|Last modified date：2023.07.18
Associate Professor / Department of Aeronautics and Astronautics, Graduate School of Engineering / Department of Aeronautics and Astronautics / Faculty of Engineering
|Last modified date：2023.07.18
|Fujio, C. and Ogawa, H., Inverse Design and Sensitivity Analysis of Scramjet Intake Using Deep Learning, 11th Asian Joint Conference on Propulsion and Power (AJCPP 2023), 2023.03.
|Ozawa, T., Yeo, S. K. and Ogawa, H., Physical Insight into Microwave Electrothermal Thruster Startup via Multi-Objective Design Optimization and Plasma Simulation, AIAA Scitech 2023 Forum, 2023.01.
|Ogawa, H., Matsunaga, M., Hew, J. K. J., Boswell, R. W., Fujio, C., Higa, Y., Watanabe, Y., Handa, T. and Ohtani, K., Characterisation of Centreline Reflection for Inward-Turning Axisymmetric Shock Waves, 22nd International Symposium on Advanced Fluid Information (AFI 2022), 2022.11.
|Higa, Y., Watanabe, Y., Handa, T., Matsunaga, M., Fujio, C., Ogawa, H. and Ohtani, K., Study on Visualization Method for Axisymmetric Shock Reflection in Supersonic Flow, 19th International Conference on Flow Dynamics (ICFD 2022), 2022.11.
|Hew, J. K. J., Matsunaga, M., Ogawa, H. and Boswell, R. W., Improved Modelling of Conical Mach Reflection Impinging on an Axis of Symmetry, 20th Australian Space Research Conference (ASRC 2022), 2022.09.
|Ueda, S. and Ogawa, H., Application of Neural Ordinary Differential Equations to Trajectory Control Laws for Lunar Landing, International Astronautical Congress (IAC 2022), 2022.09.
|Fujio, C. and Ogawa, H., Multi-Objective Design Optimization of Scramjet Intakes via Evolutionary Algorithms Assisted by Multi-Dimensional Predictive Modeling Based on Deep Learning, 2nd International Conference on High-Speed Vehicle Science and Technology (HiSST 2022), 2022.09.
|Ghosh, D. and Ogawa, H., Design and Numerical Investigation of a Hypersonic Waverider based Entry, Descent, and Landing Architecture Assisted by Supersonic Retro-Propulsion, 26th AIAA Aerodynamic Decelerator Systems Technology Conference, 2022.05.
|Akiyama, K. and Ogawa, H., Fast Prediction and Sensitivity Study of Two-Dimensional Fuel Injection Flowfields via Deep Learning, 33rd International Symposium on Space Technology and Science (33rd ISTS), 2022.02.
|Ozawa, T., Yeo, S. H., Ogawa, H. and Suraweera, M., Multi-Objective Design Optimization of Microwave Electrothermal Thruster, 33rd International Symposium on Space Technology and Science (33rd ISTS), 2022.02.
|Fujio, C. and Ogawa, H., Scramjet Intake Design Based on Exit Flow Profile via Global Optimization and Deep Learning toward Inverse Design, AIAA Scitech 2022 Forum, 2022.01.
|Yeo, S. H. and Ogawa, H., Multi-Objective Design Optimization and Uncertainty Analysis of a Downscaled Cusped Field Thruster, 2021 Asia-Pacific International Symposium on Aerospace Technology (APISAT 2021), 2021.11.
|Ogawa, H., Fujio, C., Matsunaga, M., Higa, Y., Handa, T. and Ohtani, K., Investigation on Viscous and Base Effects in Supersonic Ring Wedge Intake Flowfield, 21st International Symposium on Advanced Fluid Information (AFI 2021), 2021.10.
|Foo, Y., Ogawa, H., and Ueda, S., Survey of Low-Energy Transfers to Lunar Libration Point Orbits with Targeted L1 Transits, 2021 AAS/AIAA Astrodynamics Specialist Conference, 2021.08.
|Ueda, S. and Ogawa, H., Global Trajectory Optimization of Earth-NRHO Transfer via Multiple Impulsive Maneuvers Using Highly Parallel GPU Architecture, 2021 AAS/AIAA Astrodynamics Specialist Conference, 2021.08.
|Ueda, S. and Ogawa, H., Global Trajectory Optimization of Earth-NRHO Transfer Using Weak Stability Boundary Via GPU-Based Super-Parallelization, 31st AAS/AIAA Space Flight Mechanics Meeting, 2021.02.
|Xu, Z., Bando, M., Ogawa, H. and Hokamoto, S., Application of Halo Orbit on Extension for Launch Window Limited by Direct Earth-Mars Transfer, 31st AAS/AIAA Space Flight Mechanics Meeting, 2021.02.
|Foo, Y., Ogawa, H., Ueda, S. and Bando, M., Global Optimization of Manifold-Based Transfers to Halo and Butterfly Orbits Using Highly-Parallel GPU Architecture, 31st AAS/AIAA Space Flight Mechanics Meeting, 2021.02.
|Furutachi, K., Ogawa, H. and Ueda, S., Multidisciplinary System Design Optimization of Lunar Surface Access from Cislunar Orbit via Surrogate-Assisted Evolutionary Algorithms Using Highly-Parallel GPU Architecture, 31st AAS/AIAA Space Flight Mechanics Meeting, 2021.02.
|Fujio, C. and Ogawa, H., Multi-Objective Design Optimization and Analysis of Streamline-Traced Intakes for Scramjet-Powered Ascent Flight, AIAA Scitech 2021 Forum, 2021.01.
|Brahmachary, S. and Ogawa, H., Multi-Point Design Optimization of Busemann Based Intakes for Scramjet-Powered Ascent Flight via Surrogate-Assisted Evolutionary Algorithms, AIAA Scitech 2021 Forum, 2021.01.
|Brahmachary, S., Fujio, C., Aksay, M. and Ogawa, H., Design optimisation and off-design performance study of an axisymmetric scramjet intake for ascent flight, 8th International and 47th National Conference on Fluid Mechanics and Fluid Power (FMFP 2020), 2020.12.
|Mazumdar, R., Ogawa, H., and Pudsey, A., Reduced Order Chemical Kinetic Modeling for a Hydrogen Fueled Radical Farming Scramjet, 5th World Congress on Momentum, Heat and Mass Transfer (MHMT’20), 2020.10.
|Ogawa, H., Fujio, C., Shoesmith, B., Mölder, S., Timofeev, E., Shoev, G. and Ohtani, K., Centreline Reflection of Axisymmetric Shock Waves in Supersonic Ring Wedge Intakes, 20th International Symposium on Advanced Fluid Information (AFI 2020), 2020.10.
|Ueda, S. and Ogawa, H., Multiple Impulse Cislunar Transfer via Multi-Fidelity Approach using GPU-based Super Parallelization, 2020 Astrodynamics Specialist Conference, 2020.08.
|Brahmachary, S., Tokuda, A., Ogawa, H., Bang, J., Ahn, J., and Ueda, S., Multi-target rendezvous optimization for active debris removal via multi-fidelity approach, SICE International Symposium on Control Systems 2020, 2020.03.
|Ueda, S. and Ogawa, H., Global Trajectory Optimization Framework via Multi-Fidelity Approach Supported by Machine Learning and Primer Vector Theory for Advanced Space Mission Design, SICE International Symposium on Control Systems 2020, 2020.03.
|Roos, T., Pudsey, A., Bricalli, M., and Ogawa, H., Numerical Investigation of Upstream Cavity Enhanced Combustion in a Scramjet Combustor, 23rd AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2020.03.
|Salloum, J., Candon M., Ogawa, H., and Kodera, M., Influence of Turbulence Modelling on Combustor Flowfield in Scramjet Mode of RBCC Engine, 23rd AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2020.03.
|Brahmachary, S., Tokuda, A., Ogawa, H., Bang, J., Ahn, J., and Ueda, S., Multi-Fidelity Optimisation of Multi-Target Rendezvous Problems by Using GPU Super-Parallelisation, 11th Kyushu-University-KAIST Symposium on Aerospace Engineering, 2019.12.
|Hideaki Ogawa, Chihiro Fujio, Shuvayan Brahmachary, Taiki Watanabe, Kiyonobu Ohtani, Numerical and Experimental Investigation of Centreline Shock Reflection in Ring-Shaped Supersonic Intake Geometries, 2019.11.
|Michael Candon, Peter Driscoll, Joseph Salloum, Hideaki Ogawa, Masatoshi Kodera, Performance Design Optimization of RBCC Combustor in Ramjet and Scramjet Operation via Surrogate-Based Evolutionary Algorithms, 2019.09.
|G. Shoev, Hideaki Ogawa, Numerical Investigation on Axisymmetric and Planar Shock Reflections in Steady Viscous Flow, 2019.07.
|Julian Escalante, Ruipeng Xu, Hideaki Ogawa, Adrian Pudsey, CFD-Coupled 6-DOF Attitude & Trajectory Analysis for Hypersonic Air Vehicles, 2019.02.
|Matthew Rozek, Hideaki Ogawa, Satoshi Ueda, Toshinori Ikenaga, Multi-Objective Optimisation of NRHO-LLO Orbit Transfer via Surrogate-Assisted Evolutionary Algorithms, 2019.02.
|Christopher Hewitt, Hideaki Ogawa, Mathew Bricalli, Numerical Analysis of Thermal Loading in Dual-Bell Rocket Nozzles, 2019.02.
|Suk H. Yeo, Hideaki Ogawa, Investigation of influence of magnet thickness on performance of cusped field thruster via multi-objective design optimization, Asia-Pacific International Symposium on Aerospace Technology, APISAT 2018, 2019.01, The cusped field thruster (CFT) is a class of advanced electric propulsion (EP) technology for satellite and space missions, offering advantages over other types of EP including enhanced electron confinement owing to the magnetic mirror and reduced particle loss effects at the dielectric wall. The increasing demand for downscaling for micro-satellite class platforms while keeping performance at similar level has led to considerable efforts dedicated to physical modeling and performance characterization of downsized CFT. Multi-objective design optimization is conducted in this study by employing performance parameters of downscaled CFT, namely, thrust, total efficiency, and specific impulse as the objective functions to maximize and design parameters including anode voltage and current, mass flow rate, and inner and outer magnet radii as the decision variables. Two geometric configurations are considered, i.e., those comprising three magnets with fixed thickness and four magnets with variable thickness to gain insights into the influence of magnet thickness on the performance. Considerable effects of magnet thickness on the performance have been found, including thrust increase of up to approximately 20% and increase in specific impulse by up to approximately 10%, as compared to the configuration with fixed thickness magnets..
|Suk H. Yeo, Thomas Fahey, Hideaki Ogawa, Angus Muffatti, Paul Matthias, Daniel Kahnfeld, Maya Padivattathumana, Ralf Schneider, Multi-objective optimization and particle-in-cell simulation of cusped field thruster for micro-satellites platform, AIAA Scitech Forum, 2019, 2019.01, Electric Propulsion (EP) is a suitable propulsion technology for satellite and space missions, offering advantages over chemical propulsion in various aspects including fuel consumption hence launch cost. The cusped field thruster (CFT) offers advantages over other types of EP such as the gridded ion thruster and Hall effect thruster, with enhanced electron confinement owing to the magnetic mirror and reduced particle loss effects at the dielectric wall. The increasing demand for performance improvement of the propulsion system while downscaling for micro-satellite class platforms has led to considerable efforts dedicated to physical modeling and performance characterization of downsized CFT. In the present study a multi-objective design optimization (MDO) study has been conducted to characterize the performance to maximize three performance objectives of downscaled CFT, namely, thrust, total efficiency, and specific impulse defined by common design parameters, namely, anode voltage, anode current, mass flow rate and geometric configuration. Particle-in-cell simulations have been performed for the selected design points identified in MDO studies for verification by accurately accounting for phenomena and performance losses that originate from uncertainties and complexities associated with the thruster design and physics..
|Zheng Yang, Hideaki Ogawa, Numerical Analysis of Transonic Buffet Control Using a Two-Dimensional Bump for a Supercritical Aerofoil, Asia-Pacific International Symposium on Aerospace Technology, APISAT 2018, 2019.01, The aerodynamic behaviour of transonic flow around a supercritical aerofoil is strongly influenced by shock-wave/boundary-layer interaction (SBLI) due to compressible and viscous effects. SBLI causes undesirable effects in various manners including flow instability, drag rise, and buffet, which crucially limit the flight envelop hence operation. In this paper, a numerical investigation is conducted for an OAT15A supercritical aerofoil under a typical buffet onset condition. Unsteady Reynolds-Averaged Navier-Stokes (URANS) equation is used to simulate the compressible, viscous flowfield. A two-dimensional (2D) surface bump based on preceding research on SBLI control is employed as a flow control device. It is placed on the suction side of the aerofoil relative to the shock position, with a fixed location of 27% of the chord length. A freestream condition of Mach 0.73 and a 3.5° angle of attack have been considered for the unsteady flowfield. It has been found that the trailing edge vortices within the separation bubble have considerable influence on self-sustained shock oscillation by scrutinising the flowfields in the presence/absence of bump control. The establishment of a λ-shock structure effectively restricts the motion of the front shock leg without incurring significant re-expansion generated by the moving rear shock leg. This subsequently suppresses flow separation at the trailing edge within an acceptable range, and attenuates the periodic lift fluctuation associated with the oscillating shock movement..
|Hideaki Ogawa, Ben Shoesmith, Sannu Mölder, Evgeny Timofeev, Georgy Shoev, Kiyonobu Ohtani, Characteristics of Centreline Shock Reflection in Stunted Busemann Intakes, 2018.11.
|Suk Hyun Yeo, Hideaki Ogawa, Analysis of Effects of Magnet Configurations for Downscaled Cusped Field Thruster via Surrogate Assisted Evolutionary Algorithms, 2018.09.
|Michael Candon, Robert Carresey, Nish Joseph, Hideaki Ogawa, Pier Marzocca, Characterization of control surface freeplay with nonstationary aerodynamic loading via the hilbert-huang transform, AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2018, 2018.01, The Hilbert-Huang Transform is used to analyze the nonlinear aeroelastic response of a 2D 3DOF aeroelastic airfoil system with control surface freeplay under transonic flow conditions. Both static aerodynamic condition and dynamic aerodynamic condition, that is for accelerating freestream speed, are considered using a linearized aerodynamic model. The main aim of this paper is to provide physical insights as to the observed transition between periodic and aperiodic behavior, and the presence of a stable periodic region well below the region characterized by stable limit cycles. Physical insights towards this transition are presented by showing that multiple internal resonances exist. It is shown that the abrupt transition from aperiodic / chaotic to periodic behavior is a result of multiple internal resonances between linear and nonlinear modes. Initially a 2:1 IR between linear modes leads to a shift in the frequency composition and dynamic behavior of the system, then immediately a secondary 2:1 IR occurs between of linear and nonlinear modes which drives a stable periodic region..
|Magesh R. Ravindran, Mathew G. Bricalli, Adrian S. Pudsey, Hideaki Ogawa, Mixing characteristics of cracked gaseous hydrocarbon fuels in scramjets, 22nd AIAA International Space Planes and Hypersonics Systems and Technologies Conference, 2018, 2018.01, High-performance hydrocarbon-fuelled scramjet engines require efficient fuel-air mixing due to the relatively short flow residence time through the combustor. At high temperatures, hydrocarbon fuels react endothermically and absorb thermal energy from the surroundings. The process known as cracking becomes essential at high Mach numbers to increase the total heat-sink capacity of the fuel. This study presents the results of numerical simulations that investigate the mixing characteristics of cracked gaseous heavy hydrocarbon fuels injected through a circular, flush-wall porthole injector inclined at 45-deg to the freestream. The mixing characteristics of six fuel compositions representing various cracking efficiencies ranging from 0-100% are investigated. The mixing rates and flow structures are found to change with fuel compositions. As the cracking increases, the mixing and streamwise circulation increase for an injectant. However, the jet penetration and stagnation pressure losses decrease. The density gradients determine the strength of vorticity in the vicinity of the injector. The streamwise circulation is found to have a strong influence on the mixing and the strength of bow shock on the jet penetration. Overall, it is shown that there are mixing benefits to be gained by injecting cracked hydrocarbon fuels compared to heavy uncracked fuels in scramjets..
|Yeong Jia Boom, Kit Fong Lio, Hideaki Ogawa, Multi-objective design optimization of flow control behind backward facing steps with dielectric barrier discharge plasma actuators, AIAA Aerospace Sciences Meeting, 2018, 2018.01, In the present research, the effects of dielectric barrier discharge plasma actuators on the flow control behind a backward facing step with various step angles are analyzed. A multi-objective optimization study has been conducted by means of evolutionary algorithms assisted by surrogate modelling coupled with computational fluid dynamics. A set of decision variables including input voltage, frequency, width of generated plasma and distance from the flow inlet to the start of the generated plasma are employed for an optimization problem aiming to simultaneously minimize the total pressure loss and reattachment length, while maximizing the uniformity of the flow. The flowfields have been analyzed for selected individuals from the Pareto optimal front in comparison with the baseline and reference results in the absence of a plasma actuator. Global sensitivity analysis has been performed to identify key design parameters for flow control. It has revealed major impact of the design parameters of the DBD plasma actuator on the behavior of the flow and major improvements in performance for all three angle configurations. Flow separation has been suppressed considerably while achieving moderate improvements in the flow uniformity and total pressure loss..
|Joseph Salloum, Michael Candon, Andrew Ridings, Hideaki Ogawa, Masatoshi Kodera, Shuichi Ueda, Numerical investigation of an RBCC combustor during ramjet/scramjet mode transition, AIAA Aerospace Sciences Meeting, 2018, 2018.01, Rocket-based Combined-Cycle (RBCC) engines offer a promise for efficient and flexible propulsion over a large Mach number range by combining rocket and ramjet/scramjet technology. To achieve this, an RBCC engine uses four different modes of operation: rocket, ramjet, scramjet and dual-mode. During operation, the engine must make the transition from subsonic to supersonic combustion, i.e., ramjet to scramjet mode. The objective of this study is to gain physical insight into the ramjet-scramjet-ramjet mode transition by elucidating the underlying mechanics. Numerical simulations with chemical reactions have been performed for the transient flowfields of a two-dimensional RBCC combustor by using an unsteady Reynolds-Averaged Navier-Stokes solver. Mode transition is effected by changing the flow rate of the secondary hydrogen fuel injectors installed on the top and bottom walls of the combustor. A parametric study was conducted to investigate the characteristic and behavior of RBCC combustion in mode transition. The results indicated that transition is affected considerably by the presence and development of flow separation and pseudo-shock structures near fuel injectors. The complex effects of aerodynamic and aerothermal interactions on the transient flowfields and performance, along with a hysteresis observed between the scramjet-to-ramjet and ramjet-to-scramjet transition processes..
|Hideaki Ogawa, Georgy Shoev, Sannu Mölder, Ben Shoesmith, Téa Nicolas, Ramandeep Kaur, Evgeny Timofeev, Yevgeniy Bondar, Kiyonobu Ohtani, Shigeru Ohbayashi, Investigation on Behaviour and Characteristics of Centreline Shock Reflection in Supersonic Flow, 2017.11.
|Hideaki Ogawa, Georgy Shoev, Numerical Investigation of Viscous Effects on Centreline Shock Reflection, 2017.11.
|Mahima Katugampola, Adrian Chiem, Leonard Aguero, Hideaki Ogawa, Numerical Analysis for Supersonic Transport with Integrated Linear Aerospike Nozzles, 2017.10.
|Yeong Jia Boom, Kit Fong Lio, Hideaki Ogawa, Optimization of Backward-Facing Step Flow Control using Dielectric Barrier Discharge Plasma Actuators, 2017.10.
|Graham E. Dorrington, Hideaki Ogawa, Pavel M. Trivailo, Enceladus plume and icy body exospheric particle sampling using rotating tether and alternative architectures, 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017, 2017.01, A synopsis of missions to icy bodies, in particular ones involving the resampling of the plumes of Enceladus, is offered. Following the speculation of others, it is assumed that any microbes possibly existing in the putative water mantle of Enceladus could be swept-up by the plume. After consideration of instrument capabilities, it is concluded that no planned or proposed hypervelocity plume fly-through missions is likely to result in a definitive confirmation of such possible life. Instead, it is suggested that plume particle collection with relative encounters at ∼200 ms-1 with more relevant detection instruments, is far more likely to result in definitive confirmation. An illustrative model of the Enceladus plume is also presented to justify the need for collection of larger ice particles at altitudes of ∼3 km. To provide the recommended encounters at low velocity and altitude the potential use of tethered collection systems is briefly introduced. It is concluded that an Enceladus orbiter should be prioritized..
|Thomas Fahey, Angus Muffatti, Hideaki Ogawa, High fidelity multi-objective design optimization of a downscaled cusped field thruster, 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017, 2017.01, There is a clear demand for advanced electric propulsion systems for current and future satellite applications for a variety of commercial and research missions to reduce launch costs. The HEMP-T/CFT propulsion systems are very complex and require a detailed analysis of how design criteria influence performance. By downscaling the CFT, further propellant and system reductions would result in lower costs while maintaining high performance. The CFT concept has demonstrated significantly improved performance over the HET and GIT, however little is understood about the complexities of the interactions and interdependencies of the geometrical, magnetic and ion beam properties of the thruster. This study applies an advanced design methodology combining a modified power distribution calculation and evolutionary algorithms assisted by surrogate modeling to a multi-objective optimization for the performance optimization and characterization of the CFT. Optimization is performed for maximization of performance defined by 5 design parameters (i.e., Φa, Ia, ma, and magnet radii), simultaneously aiming to maximize 3 objectives, that is, thrust, efficiency and specific impulse. Statistical methods based on global sensitivity analysis are employed to assess the optimization results in conjunction with surrogate models to identify key design factors with respect to the 3 design objectives and additional performance measures. Significant effects of the anode power and magnet radii have been observed on the considered design criteria with the anode current exhibiting the most significant degree of influence on all 3 objectives. Several optimum design points were analyzed and one has demonstrated the most comprehensive advantages in important design criteria..
|Michael Candon, Robert Carrese, Hideaki Ogawa, Pier Marzocca, Carl Mouser, Oleg Levinskik, Walter A. Silva, Identification and characterization of a nonlinear aeroelastic system with freeplay and aerodynamic nonlinearities via higher–order spectra, 58th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2017, 2017.01, The identification of nonlinear systems in aeroelasticity poses a significant challenge for practitioners, often hampered by the complex nature of aeroelastic response data which may contain multiple forms of nonlinearity. Characterizing and quantifying nonlinearity is further complicated when the dynamic oscillations are of a high–amplitude limit cycle form, masking the underlying nonlinear contributions. In the present paper, a three– degree–of–freedom airfoil with freeplay in the control surface and transonic aerodynamics is investigated. The main form of analysis is via higher–order spectra to unveil the form of nonlinearity that i) freeplay with linearized aerodynamics and ii) freeplay with nonlinear inviscid aerodynamic phenomena will produce. It is shown that the freeplay nonlinearity with linearized aerodynamics is characterized solely by cubic interactions, i.e., the quadratic interactions are negligible. However, when considering the Euler-based CFD simulations, as the amplitude of the of the oscillations increases and Type-B shock motion becomes more apparent, the strength of the quadratic interactions becomes prominent. The findings demonstrate how the interaction between the different types of nonlinearity and the different solution methods affect the nonlinear spectral content of the system and how different forms of nonlinearity can be characterized by their higher–order spectra..
|Philipp Klink, George N.A. Coulloupas, Hideaki Ogawa, Performance analysis of RBCC-based TSTO space transportation systems via multi-objective design optimisation, 68th International Astronautical Congress: Unlocking Imagination, Fostering Innovation and Strengthening Security, IAC 2017, 2017.01, Efficient and flexible space transportation systems are fundamental to the future success of routine scientific, commercial and strategic space missions. RBCC (rocket-based combined cycle) systems comprising rockets and airbreathing engines such as ramjet and scramjets are a reusable launch propulsion concept, offering considerable advantages for space transport over traditional propulsion in various aspects, including efficiency and flexibility. Multiobjective design optimisation studies have been performed for a conceptual RBCC-based TSTO (two-stage-to-orbit) system by means of evolutionary algorithms and trajectory optimisation with respect to important design criteria. The results highlight complex and nonlinear aerodynamic and propulsion characteristics, associated with numerous design characteristics, whilst evaluating the feasibility of the transportation system and providing physical insight into key design parameters with predominant influences identified by sensitivity analysis..
|Michael Candon, Robert Carrese, Hideaki Ogawa, Pier Marzocca, Characterization of the nonlinear aeroelastic behavior of an airfoil with freeplay and aerodynamic nonlinearity, 30th Congress of the International Council of the Aeronautical Sciences, ICAS 2016, 2016.01, Higher-order spectra (HOS) are utilized to investigate the nonlinear flutter behavior of a two-dimensional pitch/plunge airfoil system in transonic flow with freeplay and aerodynamic nonlinearity. It is shown that on the route to diverging flutter the system begins with the pitching and plunging modes being uncoupled and undergoes various evolutions exhibiting quasi-periodic behavior as it moves towards an ordered state of high-amplitude periodic limit cycle behavior. New physical insights come from the bispectral densities being computed at critical stages as the system evolves from through different stages of periodicity with the coalescence of the pitching and plunging frequencies into a single coupled limit cycle. Based on these estimates the nonlinear interaction mechanisms which occur within the nonlinear aeroelastic system prior to diverging flutter can be characterized. Furthermore, aerodynamic nonlinearity in the form of Tijdeman Type-B shock motion is quantified and its effect in combination with freeplay assessed..
|Michael Candon, Hideaki Ogawa, Robert Carrese, Pier Marzocca, Identification of nonlinear aeroelastic behavior of a wing with pitching and plunging freeplay via higher-order spectra analysis, 57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2016, 2016.01, Higher-order spectra (HOS) analysis is utilized to analyze the nonlinear utter aspects of the AGARD 445.6 wing with pitching and plunging freeplay nonlinearities installed at the root. High-fidelity fluid-structure interaction simulations are conducted and the transient responses are monitored at the root and tip of the wing. The transient responses are truncated such that only the static portion of the signal remains and and the HOS are evaluated. The pitching/plunging freeplay ranges of motion and initial setting angle are varied, and the effect on nonlinear interactions and transient response are monitored. It is demonstrated that the presence of pitching freeplay is a major driver in the nonlinear phenomena, that the amplitude of the LCO is highly sensitive to the plunging freeplay range of motion whilst the presence of nonlinear interactions are dependent on interactions between the pitching and plunging freeplay effects. The application of this methodology from a practical perspective includes structural health monitoring, and the ability to identify and mitigate undesirable nonlinear aeroelastic phenomena in the design phase..
|K. Tanimizu, T. Jones, H. Ogawa, A. Pudsey, Numerical investigation of the flow structures in a quasi-axisymmetric scramjet engine, 20th Australasian Fluid Mechanics Conference, AFMC 2006, 2016.01, The flowfield characteristics of a relatively small quasi-axisymmetric scramjet vehicle at a Mach 6 flight condition have been investigated numerically. To this end, three-dimensional, compressible, turbulent, reacting flow calculations with a finite rate chemistry model consisting of 33 reactions and 13 species and two-equation SST k-ω RANS model have been performed. Hydrogen is used as the fuel and the injection pressure of fuel is varied from 1 to 7 MPa in order to study the effect of the injection pressure on the flowfields in the scramjet model. The combustion length has been found to decrease as the injection pressure increases. However, rather little thrust gain has been achieved by combustion heat release in the present configurations..
|Michael Candon, Hideaki Ogawa, Robert Carrese, Pier Marzocca, An investigation into the effect of freeplay on the nonlinear aeroelastic behavior of a wing via higher-order spectra, 26th International Conference on Adaptive Structures and Technologies, ICAST 2015, 2015.01, Higher-order spectra analysis is used to analyze the nonlinear flutter characteristics of the AGARD 445.6 wing benchmark model, modified to include freeplay structural nonlinearities in pitch and plunge at the wing root. High-fidelity coupled CFD-CSD fluid-structure interaction simulations are conducted and bispectral densities are computed from selected aeroelastic wing dynamic response signals to identify the presence of quadratic nonlinearities within the available time histories. Initially, various freeplay conditions are investigated, before focusing on the intensity of nonlinear behavior at various wing spanwise stations. The considerable effect of freeplay is clearly demonstrated as the wing enters a bounded limit cycle oscillation (LCO) with amplitudes several orders of magnitude larger than that of the case without freeplay. Nonlinear coupling is demonstrated via self-interaction of the LCO frequency and coupling between the LCO frequency and the first torsional mode, this is shown to be strongest at the root where the pitch / plunge mechanism is installed and torsion is most prominent, dissipating spanwise from the pitch / plunge mechanism as the torsional motion becomes less significant. Modal analysis, alongside analysis of the leading-trailing edge phase change and wing deformation shapes supports the findings of the HOS, generating understanding of the underlying physical attributes leading to the observed nonlinear aeroelastic phenomena..
|Robert Carrese, Pier Marzocca, Michael Candon, Hideaki Ogawa, Evolutionary shape optimization of transonic airfoils for aerodynamic and aeroelastic performance, 26th International Conference on Adaptive Structures and Technologies, ICAST 2015, 2015.01, The ongoing use and development of optimization frameworks for aircraft design is due to their ability to identify optimal and often non-intuitive shapes pertaining to the multi-disciplinary design criteria. Airfoil design is a continuously revised multi-disciplinary problem in the literature, and is pivotal to illustrate the performance of optimization frameworks involving numerical simulation, flexible shape parameterization, and intelligent evolutionary algorithms. An often overlooked component of this classic problem is to consider the dynamic aeroelastic behavior under trim conditions, which can impose explicit boundaries to the flight envelope. In this paper, a multiobjective particle swarm optimization framework is presented, pertaining to aerodynamic and aeroelastic design criteria at the trim condition. Designer preferences are used to reflect the optimal compromise between the objectives. Results of the optimization process indicate a large spread in design variable influence and interaction, and a subtle yet clear distinction between all objectives is illustrated through the final airfoil shapes obtained..
|Trent Jones, Nitin Karwa, Hideaki Ogawa, Gary Rosengarten, Flow analysis of the effect of tube geometry on the performance of pre-coolers for turbine-based hypersonic air-breathing propulsion, 7th Asia-Pacific International Symposium on Aerospace Technology, APISAT 2015, 2015.01, In this work the effect of the tube geometry on the performance of a staggered tube cross-flow heat exchanger, similar to the inlet air pre-coolers in hypersonic aircrafts and air-breathing launch vehicles, is studied using computational fluid dynamics (CFD) at sea level conditions with air velocity of up to 50 m/s. Single tube simulations showed a decrease in drag coefficient and increased utilization of tube surface area for heat exchange when elliptical or obround tubes are used instead of a circular tube. In a tube bank, the heat transfer coefficient is enhanced and the friction factor is reduced by using the elliptical and obround tubes as compared to circular tubes. Overall, for the same heat duty, elliptical and obround tube pre-coolers are lighter and compact but the pressure drop is higher than a circular tube pre-cooler..
|Tuan Quang Ho, Hideaki Ogawa, Cees Bil, Investigation on Effective Sampling Strategy for Multi-objective Design Optimization of RBCC Propulsion Systems via Surrogate-assisted Evolutionary Algorithms, Asia-Pacific International Symposium on Aerospace Technology, APISAT 2014, 2015.01, Rocket-based combined cycle (RBCC) engines are an airbreathing propulsion technology that offers considerable potential for efficient access-to-space. Successful design of RBCC-powered space transport systems requires reliable databases for both vehicle and engine performance, calling for an effective sampling method to accurately resolve non-linear characteristics in vast design space. This paper presents an optimal sampling strategy based on the function gradients to realize efficient database construction based on evolutionary algorithms and assesses its effectiveness by applying the methodology to various test functions with multiple objectives as well as surrogate models representing scramjet intake characteristics for validation..
|H. Ogawa, B. Capra, P. Lorrain, Numerical investigation of upstream fuel injection through porous media for scramjet engines via surrogate-assisted evolutionary algorithms, 53rd AIAA Aerospace Sciences Meeting, 2015, 2015.01, A multi-objective design optimization study has been conducted for upstream fuel injection through porous media applied to the first ramp of a two-dimensional scramjet intake. The optimization has been performed by coupling evolutionary algorithms assisted by surrogate modeling and computational fluid dynamics with respect to three design criteria, that is, the maximization of the mixing efficiency, total pressure saving, and fuel penetration. A distinct Pareto optimal front has been obtained, highlighting the counteracting behavior of the total pressure against fuel penetration, while the mixing performance crucially depends on the fuel/air equivalence ratio, as suggested by an additional optimization using the absolute mixing quantity. The Darcian and Forchheimer coefficients in the porous flow direction have been identified as the key design parameters in conjunction with the geometric parameters as a result of a sensitivity analysis. Flowfield visualization has revealed the presence of local hot pockets with intensely high pressure and temperature offered by a long injector positioned upstream due to augmented shock interactions..
|Graham Bell, Hideaki Ogawa, Simon Watkins, Numerical investigation on the efficiency of a plasma actuator for turbine applications, 53rd AIAA Aerospace Sciences Meeting, 2015, 2015.01, Plasma actuators are all electrical devices capable of altering flow paths and preventing separated boundary layers. The application to low pressure turbine stages in axial turbine engines offers further fuel eficiency improvements at low Reynolds numbers. Validated against wind-tunnel experiments, a numerical plasma model via steady-state RANS tur- bulence modeling simulations was developed. Reasonable agreement has been observed in the calibration of the numerical plasma model to experimental data. Further parametric studies are considered, aiming to optimize control, reduce pressure loss for turbine stages, and offset actuator power consumption. Results indicate that optimum flow control and positioning can prevent flow separation, reducing aerodynamic drag by 70% and offset power consumption inclusive of the actuator by up to 20 ± 4 %..
|Michael J. Candon, Hideaki Ogawa, Graham E. Dorrington, Thrust augmentation optimization through supersonic after-burning in scramjet engine nozzles via surrogate-assisted evolutionary algorithms, 53rd AIAA Aerospace Sciences Meeting, 2015, 2015.01, Scramjets are a class of hypersonic airbreathing engine that are associated with realizing the technology required for economical, reliable and high-speed access-to-space and atmospheric transport. The expanding flow in the scramjet nozzle comprises of unburned hydrogen which under ideal conditions, can be utilized to introduce an after-burning scheme. After-burning augments the thrust produced by the scramjet nozzle and creates a more robust nozzle design. This paper presents a single-objective design optimization considering three design variables with the objective of producing maximum thrust augmentation. It is found that significant levels of thrust augmentation are produced based upon contributions from increased pressure, mass flow and energy in the nozzle. Further understanding of the phenomenon by which thrust augmentation is being produced is provided in the form of variance-based global sensitivity analysis, force contribution breakdowns, analysis of the nozzle flowfields, analysis of the surface pressure and shear stress distributions acting on the nozzle wall and analysis of the combustion efficiency..
|Masatoshi Kodera, Hideaki Ogawa, Sadatake Tomioka, Shuichi Ueda, Multi-objective design and trajectory optimization of space transport systems with RBCC propulsion via evolutionary algorithms and pseudospectral methods, 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014, 2014.01, In this study, a multi-objective design optimization coupling evolutionary algorithms and trajectory optimization via pseudo-spectral methods has been conducted for the first stage of two-stage to orbit (TSTO) system with a rocket-based combined cycle (RBCC) engine which combines rockets and ramjets by blending two kinds of vehicle configurations with different aerodynamic characteristics. The design criteria include the minimization of fuel consumption and the maximization of the final Mach number up to a separation of the TSTO system at the maximum altitude under certain ranges of acceleration and dynamic pressure. The optimization results reveal a counteractive trend between the final Mach number and fuel mass ratio and the major impact of effective specific impulse on those two objectives, which is mainly controlled by thrust throttling parameter within the trajectory optimization. In addition, the RBCC-powered vehicle tends to fly at lower altitude to attain the minimum fuel mass ratio, in contrast to the case for maximum final Mach number, which is attributed to the hybrid aerodynamic performance of the two configurations. The insight gained here can be usefully applied to the design of high-performance RBCCpowered vehicles..
|Masatoshi Kodera, Hideaki Ogawa, Sadatake Tomioka, Shuichi Ueda, Multi-objective design and trajectory optimization of space transport systems with RBCC propulsion via evolutionary algorithms and pseudospectral methods, 52nd Aerospace Sciences Meeting 2014, 2014.01, In this study, a multi-objective design optimization coupling evolutionary algorithms and trajectory optimization via pseudo-spectral methods has been conducted for the first stage of two-stage to orbit (TSTO) system with a rocket-based combined cycle (RBCC) engine which combines rockets and ramjets by blending two kinds of vehicle configurations with different aerodynamic characteristics. The design criteria include the minimization of fuel consumption and the maximization of the final Mach number up to a separation of the TSTO system at the maximum altitude under certain ranges of acceleration and dynamic pressure. The optimization results reveal a counteractive trend between the final Mach number and fuel mass ratio and the major impact of effective specific impulse on those two objectives, which is mainly controlled by thrust throttling parameter within the trajectory optimization. In addition, the RBCC-powered vehicle tends to fly at lower altitude to attain the minimum fuel mass ratio, in contrast to the case for maximum final Mach number, which is attributed to the hybrid aerodynamic performance of the two configurations. The insight gained here can be usefully applied to the design of high-performance RBCCpowered vehicles..
|H. Ogawa, M. Kodera, S. Tomioka, S. Ueda, Multi-phase trajectory optimization for access-to-space with RBCC-powered TSTO via surrogated-assisted hybrid evolutionary algorithms incorporating pseudo-spectral methods, AIAA AVIATION 2014 -19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2014, 2014.01, A multi-objective design optimization study coupling evolutionary algorithms and trajectory optimization via pseudo-spectral methods has been conducted for two-stage to orbit (TSTO) system with a rocket-based combined cycle (RBCC) comprising airbreathing components besides rocket engines, aiming to examine its feasibility to achieve efficient access to space, particularly to the international space station. The optimization has been performed with respect to three important design criteria, that is, the maximization of the final velocity, altitude, and mass at the terminus of the orbiter trajectory under certain constraints of acceleration and dynamic pressure. The results have revealed complex interactions of numerous design parameters and a counteractive trend between the final velocity and mass. Most influential parameters have been identified from trajectory investigation and sensitivity analysis, providing insights into the design requirements needed to fulfill the desired mission with the vehicle and propulsion configurations considered here..
|G. W. Bell, H. Ogawa, S. Watkins, Numerical investigation on flow control effects of plasma actuators for subsonic aerofoils in turbine applications, 19th Australasian Fluid Mechanics Conference, AFMC 2014, 2014.01, Plasma actuators are all electrical devices capable of altering flow paths and reattaching separated boundary layers. The application to low pressure turbine stages in axial turbine engines indicates further fuel efficiency improvements at low Reynolds numbers. Using wind tunnel experiments, a numerical plasma model through steady-state simulations with RANS turbulence modeling was developed. Reasonable agreement has been observed in the calibration of the numerical plasma model to experimental data. Further parametric studies are considered, aiming to optimize control, reduce pressure loss for turbine stages, and reduce actuator power consumption..
|H. Ogawa, C. Y. Wen, Y. C. Chang, Physical insight into fuel mixing enhancement with backward-facing step for scramjet engines via multi-objective design optimization, 29th Congress of the International Council of the Aeronautical Sciences, ICAS 2014, 2014.01, Fuel injection into crossflow behind a backwardfacing step is studied by means of multi-objective design optimization, aiming at fuel/air mixing for supersonic combustion of scramjet propulsion. A variety of injector configurations have been examined in the optimization process using evolutionary algorithms in conjunction with local search methods and surrogate modeling. Data mining has been performed by applying statistical techniques including variance-based sensitivity analysis to the surrogate models constructed with solutions from computational fluid dynamics. The injection angle and backward step height have been found to be the most influential design parameters on the mixing performance for the configurations considered in this study..
|G. E. Dorrington, H. Ogawa, J. McCarthy, R. Carrese, Simulation and experimental testing of Leonardo da Vinci's helical rotor, 19th Australasian Fluid Mechanics Conference, AFMC 2014, 2014.01, Preliminary thrust tests carried-out on a 0.5 metre diameter, helical rotor based on a sketch by Leonardo da Vinci are presented, along with the results of computational flow simulation. Some of the key geometric variables that define the helical rotor and their influence on the maximum achievable thrust level are also discussed. It is concluded that with sufficient input power, da Vinci's helical rotorcraft could achieve hovering flight; however, the technical challenges involved in a developing a free-flight hovering demonstrator would be formidable..
|M. J. Candon, H. Ogawa, G. E. Dorrington, Thrust augmentation by after-burning in a scramjet nozzle, 19th Australasian Fluid Mechanics Conference, AFMC 2014, 2014.01, A numerical study of scramjet after-burning through the injection of liquid oxygen into the nozzle is conducted. A maximum thrust augmentation of 300% is found. An understanding of the thrust augmentation phenomenon is provided in the form of a force contribution breakdown, analysis of the nozzle flowfields and finally the analysis of the surface pressure and shear stress distributions acting upon the nozzle wall..
|Hideaki Ogawa, R. R. Boyce, Computational investigation of fuel injection with various injector geometries and mixing into hypersonic crossflow in scramjet engines, 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013, 2013.08, Efficient fuel/air mixing plays a crucial role in successful operation of hypersonic airbreathing engines, particularly scramjets, where fuel must be injected into high-speed crossflow and mixed with air at an extremely short timescale. This paper presents the results of a numerical study that investigates the effects of various orifice shapes on fuel mixing into hypersonic airflow at Mach 5, aiming at the application to scramjet operation at Mach 10. The performance of the injectors are assessed with respect to various criteria such as the mixing efficiency, streamwise circulation, total pressure recovery, and fuel penetration. The injection flowfields are scrutinized in order to identify the key geometric features and underlying flow mechanism that are responsible for mixing enhancement, with particular focus on the interactions of the jet plume with streamwise vortices..
|H. Ogawa, R. R. Boyce, Multi-objective design optimization of fuel injection for mixing enhancement in scramjets by using surrogate-assisted evolutionary algorithms, 18th AIAA/3AF International Space Planes and Hypersonic Systems and Technologies Conference 2012, 2012.12, Scramjet propulsion is a promising hypersonic airbreathing technology that can enable flexible and economical systems for access-to-space and atmospheric cruise in both civilian and strategic applications. Fuel injection and efficient mixing play a crucial role in scramjet operation, which depends critically on the sequential flow process, particularly for scramjet configurations featuring upstream fuel injection. However, designing high-performance injection systems represents a substantial challenge to conventional design approaches due to complex flowfields introduced by highly coupled aerodynamic phenomena. The present study is conducted by applying an advanced methodology combining computational fluid dynamics and evolutionary algorithms assisted by surrogate modeling to a multi-objective optimization problem for high-performance injector design, assuming scramjet operation at Mach 7.6. Optimization is performed for elliptical injector configurations defined by four design parameters, namely, injection angle, spacing, aspect ratio, and hole radius, simultaneously aiming to maximize three objectives, that is, fuel/air mixing, total pressure recovery and fuel penetration into air. Flowfields are scrutinized for selected injector configurations and global sensitivity analysis is applied to the surrogate models trained during the optimization, in order to gain physical insight into underlying flow mechanism and to identify key design factors for mixing enhancement. It has been found that the injection angle and aspect ratio are primarily responsible for fuel/air mixing efficiency, while fuel penetration largely depends on the injector spacing in conjunction with the injection angle..
|A. Saha, T. Ray, Hideaki Ogawa, R. Boyce, Robust design optimization of high-performance axisymmetric scramjets based on surrogate-assisted evolutionary algorithms, 28th Congress of the International Council of the Aeronautical Sciences 2012, ICAS 2012, 2012.12, Hypersonic airbreathing engines offer great potential for reliable and economical access-tospace and high-speed atmospheric cruise for both civilian and strategic applications. Scramjet (supersonic combustion ramjet) propulsion, in particular, is a promising technology to materialize efficient and flexible transport systems by removing the need to carry oxidizers and other limitations of rocket engines. In the actual development procedure of aerospace applications, the design for fabrication is carefully determined in consideration of various requirements and criteria, based on the optimal results obtained in numerical analysis and experiments. This stage typically involves a significant amount of engineering activities and human-related factors, which may well give rise to unexpected errors, uncertainty, and accuracy loss in the design values. Discrepancies in the design between the numerical/analytical solutions and the actual product can also arise during operation, originating from various factors such as structural deformation due to aerodynamic loads and surface ablation due to aerothermal heating in hypersonic flight. It is desirable that such discrepancies do not drastically affect the performance of the design. In this work, we present our findings of Multi-objective robust design optimization of the nozzle and external contour of an axisymmetric scramjet. We analyze the effect that uncertainties in the design variables can have on the final solutions and try to understand the behavior from the physical point of view..
|A. L. Grainger, R. R. Boyce, S. C. Tirtey, H. Ogawa, G. Paniagua, S. Paris, The unsteady flow physics of hypersonic inlet starting processes, 18th AIAA/3AF International Space Planes and Hypersonic Systems and Technologies Conference 2012, 2012.12, A 2D numerical investigation was undertaken utilising transient, time-accurate, RANS computational fluid dynamics, with the aim of investigating the influence of viscous and unsteady effects when attempting to start a hypersonic scramjet inlet. A variable geometry inlet starting mechanism incorporating sliding doors was utilised, with the two doors initially extending upstream from the scramjet leading edge. After establishing a steady-state solution, the doors were retracted up and over the inlet and the resulting flow field captured. A started flow regime was achieved only when retracting the doors at such a speed (0.1ms total retraction time) that at no point could quasi-steady Kantrowitz assumptions be applied to the internal flow field. Viscous effects were seen to play a significant role in the inlet starting process, with unstart being obtained earlier for lower Reynolds number conditions. Shockwave boundary layer interactions (SWBLI) were found to be the key driver behind inlet unstart..
|H. Ogawa, S. Mölder, R. R. Boyce, Numerical investigation of diaphragm mass and viscous effects on pulse starting of axisymmetric scramjet inlets, 18th Australasian Fluid Mechanics Conference, AFMC 2012, 2012.01, Scramjets are a promising hypersonic airbreathing technology for economical access-to-space and atmospheric transport. Reliable scramjet inlet starting is of crucial importance for successful scramjet operation. It is shown that unsteady flow, resulting from the rupture of a diaphragm, can result in a steady started inlet flow. Time-accurate computations illustrate flow and wave motion during the unsteady starting process. The effects of viscosity and diaphragm mass on the inlet flowfields are investigated by time-accurate computational simulations..
|H. Ogawa, Y. Alazet, A. Pudsey, R. R. Boyce, A. Isaacs, T. Ray, Full flow-path optimization of axisymmetric scramjet engines, 17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2011, 2011.12, Scramjet propulsion is a hypersonic airbreathing technology that offers the great potential for economical and flexible access to space and high-speed atmospheric transport. This paper presents the results and physical insight obtained in a design optimization study conducted for axisymmetric scramjet engines. A single-objective optimization has been performed to maximize the performance of a full flow-path scramjet configuration in the presence of nonuniform upstream fuel injection represented by a set of geometric parameters and injection scaling factors. Use is made of a state-of-the-art design methodology coupling a high-fidelity CFD code with an advanced optimization capability based on evolutionary algorithms assisted by surrogate modeling. The flowfields have been investigated to identify key factors and gain insight into underlying physics particularly in comparison with premixed fuel/air flowfields. The optimum flowfield with fuel injection is characterized by a mixed supersonic/subsonic flow regime similar to a transitional mode. The optimum design has been achieved by maximizing the nozzle thrust while reducing skin friction drag by boundary-layer combustion, although it represents a sensitive flowfield due to the delicate mechanism upon which it relies..
|Russell R. Boyce, Sandy C. Tirtey, Laurie Brown, Michael Creagh, Hideaki Ogawa, SCRAMSPACE
Scramjet-based Access-to-Space Systems, 17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2011, 2011.12, Scramjet-based launch systems offer considerable promise for safe, reliable and economical access to space. Through both flight and ground tests, leveraging Australia's world leadership in scramjet R&D, the SCRAMSPACE project is designed to answer key scientific and technological questions and build an industry-ready talent pool for a future Australian space industry..
|H. Ogawa, R. R. Boyce, Physical insight into scramjet inlet behaviour via multi-objective design optimisation, 27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010, 2010.12, Scramjet propulsion is a promising technology for reliable and economical access to space and high-speed atmospheric transport. The inlet plays a key role in determining the performance of scramjets, in particular for the axisymmetric class of scramjet engines that are currently explored due to their advantages in numerous aspects. In the present study a multi-objective design optimisation (MDO) has been conducted with respect to four major inlet design criteria: compression efficiency, drag, adverse pressure gradient, and exit temperature. The former three criteria are used as the objective functions and the last as the constraint function to evaluate the inlet flowfields in the state-of-the-art coupled CFD / MDO approach. The influential parameters and key physics have been identified by scrutinising the flowfields that have been obtained as an outcome of the optimisation..
|Hideaki Ogawa, Alex L. Grainger, Russell R. Boyce, Inlet starting of high-contraction axisymmetric scramjets, 16th AIAA/DLR/DGLR International Space Planes and Hypersonic Systems and Technologies Conference, 2009.12, Reliable in-flight starting of the inlet is of critical importance for the successful operation of scramjet engines, particularly axisymmetric configurations with high contraction inlets. The present research is undertaken to examine the capability of various inlet starting methods based on two principles: unsteady flow effects and variable geometries. Timeaccurate viscous computations have been performed to investigate the transitional flowfields introduced by a variety of methods that are applicable to axisymmetric geometries. Parametric studies have been conducted for instantaneous rupture of conical diaphragms and addition of bleed slots, which induce highly unsteady flow phenomena. Several methods employing variable inlet geometries have been tested for the latter principle, including opening doors, rocket plugs and sliding doors (or diaphragm erosion). Successful inlet starting has been achieved as a result of unsteady transition induced by diaphragm rupture and quasi-steady transition due to the sliding door opening process. In particular, a bleed addition to the diaphragm rupture method has been found to be highly effective and pronounced flow stability has been observed in the sliding door process..
|H. Ogawa, H. Babinsky, Shock / boundary-layer interaction control using three-dimensional bumps in supersonic engine inlets, 46th AIAA Aerospace Sciences Meeting and Exhibit, 2008.12, The effects of three dimensional bump control on separated shock-wave / boundarylayer interactions have been investigated experimentally at M ∞ = 1.5, aiming to reduce total pressure losses incurred by strong normal shock / boundary-layer interactions. Such a situation occurs, for example, inside mixed-compression supersonic engine inlets or on external-compression inlets. Various bump configurations have been tested and their effects have been evaluated in various aspects such as total pressure recovery and boundary-layer thickness. Without control, the normal shock caused a region of relatively two-dimensional separation. Three-dimensional bumps commonly broke up this separation into individual regions of attached and separated flow, giving an overall reduction of the magnitude of separation. Fairly two-dimensional λ-shock structures and streamwise vortex pairs have been observed in all tested configurations. A configuration comprising multiple long, high, narrow rounded bumps has demonstrated the best performance, producing an appreciable total pressure saving as much as 30% owing to a λ-shock benefit with minimum viscous penalty from localised separation..
|H. Ogawa, H. Babinsky, M. Pätzold, T. Lutz, Shock / boundary-layer interaction control using three-dimensional bumps for transonic wings, 45th AIAA Aerospace Sciences Meeting 2007, 2007.07, Three-dimensional bumps have been developed and investigated, aiming at the two major objectives of shock-wave / boundary-layer interaction control, i.e. drag reduction and suppression of separation, simultaneously. An experimental investigation has been conducted for a default rounded bump in channel now at University of Cambridge and a computational study has been performed for a spanwise series of rounded bumps mounted on a transonic aerofoil at University of Stuttgart. Observed in both cases are wave drag reduction owing to A-shock structures produced by three-dimensional surface bumps and mild control effects on the boundary layer. The effects of rough surface and tall extension have been investigated as well as several geometric variations and multiple bump configurations. A double configuration of narrow rounded bumps has been found to best perform amongst the tested, considerably reducing wave drag through a well-established A-shock structure with little viscous penalty and thus achieving substantial overall drag reduction. Counter-rotating streamwise vortex pairs have been produced by some configurations as a result of local flow separation, but they have been observed to be confined in relatively narrow wake regions, expected to be beneficial in suppressing large-scale separation under off-design condition despite increase of viscous drag. On the whole a large potential of three-dimensional control with discrete rounded bumps has been demonstrated both experimentally and numerically, and experimental investigation of bumps fitted on a transonic aerofoil or wing is suggested toward practical application..
|H. Ogawa, H. Babinsky, Experimental investigation of 3D shock / boundary layer interaction control in transonic flows, 44th AIAA Aerospace Sciences Meeting 2006, 2006.12, A novel supersonic wind tunnel setup is proposed to enable the investigation of control on a normal shock wave. Previous experimental arrangements were found to suffer from shock instability. Wind tunnel tests with and without control have confirmed the capability of the new setup to stabilise a shock structure at a target position without changing the nature of the shock wave / boundary layer interaction flow at M∞ = 1.3 and M ∞ = 1.5. Flow visualisation and pressure measurements with the new setup have revealed detailed characteristics of shock wave / boundary layer interactions and a λ-shock structure as well as benefits of control in total drag reduction in the presence of 3D bump control..
|Holger Babinsky, Hideaki Ogawa, Three-dimensional SBLI control for transonic airfoils, 3rd AIAA Flow Control Conference, 2006.12, The application of shock control to transonic airfoils and wings has been demonstrated widely to have the potential to reduce wave drag. Most of the suggested control devices are two-dimensional, that is they are of uniform geometry in spanwise direction. Examples of such techniques include contour bumps and passive control. Recently it has been observed that a spanwise array of discrete three-dimensional controls can have similar benefits but also offer advantages in terms of installation complexity and drag. This paper describes research carried out in Cambridge into various three-dimensional devices, such as slots, grooves and bumps. In all cases the control device is applied to the interaction of a normal shock wave (M=1.3) with a turbulent boundary layer. Theoretical considerations are proposed to determine how such fundamental experiments can provide estimates of control performance on a transonic wing. The potential of each class of three-dimensional device for wave drag reduction on airfoils is discussed and surface bumps in particular are identified as offering potential drag savings for typical transonic wing applications under cruise conditions..
|H. Ogawa, H. Babinsky, Evaluation of wave drag reduction by flow control, 43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005.12, An analytical expression is proposed to estimate the wave drag of an aerofoil equipped with shock control. The analysis extends the conventional approach for a single normal shock wave, based on the knowledge that all types of successful shock control on transonic aerofoils cause bifurcated λ-shock structures. The influence of surface curvature on the λ-shock structure has been taken into account. The extended method has been found to produce fairly good agreement with the results obtained by CFD methods while requiring negligible computational effort. This new formulation is expected to be beneficial in the industrial design process of transonic aerofoils and wings where a large number of computational simulations have to be performed..