Hisashi Kihara | Last modified date：2022.05.24 |

Assistant Professor /
Thermophysics and fluid mechanics /
Department of Aeronautics and Astronautics /
Faculty of Engineering

**Presentations**

1. | Hideto TAKASAWA, Yusuke TAKAHASHI, Nobuyuki OSHIMA, Hisashi KIHARA, Study on Mitigation of Reentry Blackout by Surface Catalysis Effects in Arc-Heated Wind Tunnel , Aerospace Europe Conference 2020, 2020.02, Reentry blackout is one of the most important problems during the atmospheric reentry. In this study, we demonstrated a new mitigation method for the reentry blackout using surface catalysis effects, conducting an experiment using arc-heated wind tunnel. Firstly, for a feasibility study, we carried out plasma flow and electromagnetic waves analyses to reproduce blackout environment for non-catalysis and finite catalysis cases in the JAXA/ISAS 1MW arc-heated flow. In the numerical analysis, the electromagnetic wave was completely blocked due to reentry blackout for the case of the non-catalytic wall. On the other hand, for the case of finite catalytic wall, it was confirmed that the electromagnetic wave propagates. From the experimental results, reentry blackout occurred when using alumina as a low catalytic material. On the other hand, for the case of copper as a high catalytic material, it was found that reentry blackout is avoided.. |

2. | Soomin Park, Hisashi Kihara, Ken-Ichi Abe, Numerical study on the condensed and frozen water vapor on a flat plate using an open source code, 10th AIAA Atmospheric and Space Environments Conference, 2018, 2018.06, Numerical study on the condensed and frozen vapor on a flat plate was performed to estimate the trends of the freezing of water vapor and its thickness. For the simulation of the phase change of water vapor for the freezing, VOF(Volume of Fluid) method was used. As the freezing area growth, we investigated the flow-velocity variation in the wall-normal direction. Zero-velocity region in the frozen layer was calculated using the Carman-Kozeny equation deriving from the Darcy law in the momentum equation. The phase change rate was assumed to be mainly related the temperature difference between a plate and atmosphere. Basic concept of the freezing phenomenon was combined with the condensation vapor schematics. The calculation for the volumetric generation rate and the freezing rate of water-vapor was controlled by the thermophysical approaches and the enthalpy-porosity method to model the condensation and the freezing, respectively. The numerical simulation was conducted using an open source code, named OpenFOAM®. The obtained results were compared to the corresponding references for the variation of the frozen thickness by the phase change. The comparison of the prediction results with the reference data showed god agreement. Also, positive possibilities of the performance for obtaining better results are expected by using additional complements in further studies.. |

3. | S. Nozawa, T. Kanzaka, Hisashi Kihara, Ken-Ichi Abe, Experimental and numerical studies of spallation particles ejected from a light-weight ablator, 61st International Astronautical Congress 2010, IAC 2010, 2010, During atmospheric entry, thermal protection material (ablator) is strongly heated by aerodynamic heating. Due to this fact, micro-order particles are generated and ejected from an ablator surface, which is called 'Spallation'. In the previous ground experiments in an arc-heated facility, the presence of spalled solid particles has been confirmed upstream of a detached shock wave or a stagnation-point boundary layer. Spallation phenomena are considered to be a possible cause of increasing heat-transfer rates on an ablator surface in the downstream region. To estimate the effect of a spalled particle on an ablator, correct values of particle parameters (e.g., size, flight velocity, position) are needed. Therefore, we carried out the heating experiment for a trial manufactured light-weight ablator, and then detailed parameters for each particle were analyzed directly from the visualized pictures. As for the visualization method, the in-line holography method, that uses a recorded hologram pattern appearing behind of an illuminated particle by a collimated laser beam, was applied to evaluate the particle parameters. Moreover, the flight path of a single spallation particle was also numerically analyzed in the present study. As a result, some particles ejected from an ablator surface were visualized in the upstream region and their parameters were evaluated successfully. This fact indicates the availability of the in-line holography method for evaluation of spallation-particle parameters. By using the obtained particle parameters, the effect of a spalled particle on an ablator surface was estimated.. |

4. | Minseok Jung, Hisashi Kihara, Ken-Ichi Abe, Yusuke Takahashi, Numerical simulation of plasma flows and radio-frequency blackout in atmospheric reentry demonstrator mission, 47th AIAA Fluid Dynamics Conference, 2017, 2017.01, Numerical simulations of plasma flows and electromagnetic waves around a reentry vehicle were performed to estimate the radio-frequency blackout. The plasma flows in the shock layer and wake region were calculated using computational fluid dynamics technique. The simulation of electromagnetic waves around a reentry vehicle was conducted using a frequency-dependent finite-difference time-domain method with the plasma properties obtained by computational fluid dynamics. The numerical simulations were performed for the atmospheric reentry demonstrator at various altitudes based on the reentry orbit data. Three cases of the numerical simulations, i.e., an axisymmetric model, a three-dimensional model with non-catalytic wall and finite-catalytic wall, were performed for evaluating the effects of angle of attack and catalytic wall on the radio-frequency blackout. The formations for the number density of electrons that is an important parameter in evaluating the radio-frequency blackout were greatly changed by these three cases. The simulation model was validated based on the signal loss history of the experimental flight data. The simulation results using a three-dimensional model with finite-catalytic wall showed better agreement with the measured results compared to other two cases.. |

5. | Symposium on Shock Waves in Japan. |

6. | チョウ ヤンロン, Hisashi KIHARA, 安倍 賢一, Performance of an anisotropy-resolving subgrid-scale model for predicting turbulent channel flow with wall roughness, 8th International Symposium on Turbulence, Heat and Mass Transfer 8th, 2015.09, Large eddy simulation (LES) of a turbulent channel flow with wall roughness on one side was performed by adopting an anisotropy-resolving subgrid-scale (SGS) model at a shear Reynolds number Reτ=395. . |

7. | Y. Zhang, H. Kihara, K. Abe, Performance of an anisotropy-resolving subgrid-scale model for predicting turbulent channel flow with wall roughness, 8th International Symposium on Turbulence, Heat and Mass Transfer, THMT 2015, 2015.01, Large eddy simulation (LES) of a turbulent channel flow with wall roughness on one side was performed by adopting an anisotropy-resolving subgrid-scale (SGS) model at a shear Reynolds number = 395. To investigate the grid dependency of the LES results caused by the SGS model, three grid resolutions were tested under the same definition of a roughness shape by using the immersed boundary method. The obtained results were compared with the direct numerical simulation data without roughness (flat wall) and discussed using general knowledge in this kind of flow fields as reference. The primary concern was focused on how the present SGS model could reduce the grid dependency as well as the affects of roughness on the mean velocity and turbulent stresses.. |

8. | Yu Minghao, Yusuke Takahashi, Hisashi KIHARA, Ken-ichi ABE, Kazuhiko Yamada, Takashi ABE, Satoshi Miyatani, Thermal Nonequilibrium Modeling of an Air Inductively Coupled Plasma Flow, 飛行機シンポジウム, 2014.10, Numerical investigation of thermal nonequilibrium inductively coupled plasma (ICP) flow was carried out to study the physical properties of the flow inside a 10-kW ICP wind tunnel with the working gas being air. The flow field was described by two-dimensional compressible axisymmetric Navier-Stokes (N-S) equations that took into account 11 species and 49 chemical reactions. A four-temperature model was adopted to model thermal nonequilibrium process in the discharge torch and vacuum chamber. The magnetic vector-potential equations were tightly coupled with the flow-field equations to describe the heating process by inductive discharge. The characteristics of air ICP flow such as thermal nonequilibrium, inductive discharge, and effects of Lorentz forces became clear through the present study.. |

9. | Naoki Kawano, Hisashi KIHARA, Ken-ichi ABE, Three-Dimensional Numerical Study of High Temperature Flow Field around an Experimental Atmospheric Re-Entry Vehicle, The 5th Asian Joint Workshop on Thermophysics and Fluid Science, 2014.09. |

10. | The Difference by Line of Sight in Emission Spectroscopy around Stagnation Point in an Arc Heated Wind Tunnel . |

11. | 喩 明浩, Yusuke Takahashi, Hisashi Kihara, Ken-ichi Abe, Kazuhiko Yamada, Takashi Abe, Numerical Simulation of Nonequilibrium Inductive Plasma Flow Coupled with Electromagnetic Field Calculation, 29th International Symposium on Rarefied Gas Dynamics, 2014.06, Numerical investigation of nonequilibrium inductively coupled plasma (ICP) flow was carried out to study the physical properties of the flow inside a 10-kW ICP torch with the working gas nitrogen. The flow field was described by two-dimensional compressible axisymmetric Navier-Stokes (N-S) equations that took into account 5 species and 8 chemical reactions. The magnetic vector potential equations were tightly coupled with flow field equations to describe the heating process by inductive discharge. A four-temperature model was adopted to model thermal nonequilibrium process in the discharge torch. The characteristics of ICP flow such as thermal nonequilibrium, inductive discharge, strong effects of Lorentz forces become clear through the present study.. |

12. | Spectroscopic Measurements of a Shock Wave from the Model using an Optical Fiber. |

13. | Osamu URUMA, Hisashi Kihara, Ken-ichi Abe, An Improvement of Hybrid LES/RANS Model for Complex Turbulence with the Aide of an Anisotropy-Resolving Subgrid-Scale Model , 29th Internatonal Symposium on Space Tchnology and Sience, 2013.06, We propose a new Hybrid LES/RANS Model (HLR) which combines large eddy simulation (LES) with the Reynolds-averaged Navier-Stokes (RANS) equation with the aide of an anisotropy-resolving subgrid-scale (SGS) model based on a scale-similarity model 4). We find that the introduction of an SGS anisotropic term give a reasonable influence on the transition between RANS and LES. To investigate the model performance, the proposed model is applied to fully-developed plane channel flows with various grid resolutions and at several Reynolds numbers. For further investigation, we apply the present model to high Reynolds-number complex turbulent flows of practical interest. The Ahmed body with the 25° angle of the rear slant which the Reynolds number based on length of is Re=2.78×10⁶ is selected for verification of the present model. For the flow structure, the result of HLR model shows similar to that of experiment in coarse and fine grid. The value of the friction drag coefficient of HLR model has a smaller the grid dependence than that of LES and corresponds to that of experimental. However, the pressure drag is underestimated. As the result, the drag coefficient of Ahmed body is underestimated.. |

14. | 喩 明暁, 木原 尚, 安倍 賢一, Numerical Investigation on Plasma Flow in Low Power Inductively Coupled Plasma Wind Tunnel, The 4th Asian Symposium on Computational Heat Transfer and Fluid Flow, 2013.06, [URL]. |

15. | 松田 貴幸, 木原 尚, 安倍 賢一, Numerical Study of Thermochemical Nonequilibrium Flow around Reentry Capsule and Estimation of Aerodynamic Heating, The 7th Asian Pacific Conferenc on Aerospace Technology and Science, 2013.05, [URL], Numerical simulation of the flow fields was performed for the mission of Apollo AS-202 to investigate the influence of the laminar-turbulent transition position in the boundary layer around a reentry capsule on the heat flux at the wall. For this purpose, we intentionally varied the laminar-turbulent transition position and the obtained results were compared. It turned out that the transition position had a big influence on the heat flux at the wall in the forebody region. On the other hand, in the afterbody region, some discrepancies were seen compared with the experimental data. This is thought to be caused by the lack of considering the effects of the radiation heating and the radiation equilibrium, as well as the axisymmetric flow assumption.. |

16. | 木原 尚, 平田 尚也, Ken-ichi Abe, A Study of Thermal Response and Flow Field Coupling Simulation around HAYABUSA Capsule Loaded with Light-weight Ablator, The 11th International Symposium on Experimental and Computational Aerothermodynamics of Internal Flows, 2013.05, [URL], The numerical simulation of flow field around HAYABUSA capsule with light-weight ablator thermal response coupled with pyrolysis gas flow inside ablator was carried out. In addition, the radiation from high temperature gas around the capsule was tightly- coupled with flow field. The HAYABUSA capsule reentered the atmosphere about 12 km/sec in velocity and Mach number about 30. During such an atmospheric entry, space vehicle is exposed very savior aerodynamic heating due to convection and radiation. In this study, HAYABUSA capsule was treated as a typical model of the atmospheric entry spacecraft. The light-weight ablator had porous structure, and permeability was an important parameter to analyze flow inside ablator. In this study, permeability was a variable parameter depended on density of ablator. It found that the effect of permeability of light-weight ablator was important with present analysis.. |

17. | Yusuke Takahashi, Takashi Abe, Hiroki Takayanagi, Masahito Mizuno, Hisashi Kihara, Ken-Ichi Abe, Nonequilibrium plasma flow properties in arc-heated wind tunnels, 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2012.06, Turbulent plasma flows in arc heaters such as JAXA 750 kW, NASA 20 MW and Kyushu University 20 kW facilities were investigated and the distributions of flow-field properties were successfully obtained. For this purpose, an integrated analysis model to simulate various-scale arc-heated flows with high accuracy was developed. The turbulent flow field was described by the Navier-Stokes equations with a multitemperature model, which was tightly coupled with electric-field and radiation-field calculations. An accurate and low-cost radiation model and a low-Reynolds number two-equation turbulence model were introduced into the flow-field simulation. Arc discharge in constrictor section and expansion processes in nozzle section play key roles for forming an arc-heated flow. Thus, it is important to correctly model those phenomena for predicting the high-enthalpy flow properties accurately. To validate the present numerical model, the computed results were compared with the corresponding experimental data for the mass-averaged enthalpy, temperatures and number density. Through the comparison of the predicted results with detailed experimental data obtained by spectroscopic and laser-induced fluorescence techniques, the present integrated analysis model was validated. In addition, the mechanisms of energy input by discharge and energy loss were discussed with distributions of the temperature and heat flux derived from the arc column. Although it was indicated that more detailed discharge model is possibly required in order to describe arc discharge with higher accuracy, the present flow-field model was found to give generally good agreement for various operating conditions of the facilities.. |

18. | Numerical study of Heat-Resistance Performance for Thermochemical Non-equilibrium Flow around a Supserorbital Re-entry Capsule. |

19. | Numerical study of Heat-Resistance Performance for Thermochemical Non-equilibrium Flow around a Supserorbital Re-entry Capsule. |

20. | Improvement of Predictive Performance of Thermal-Response Analysis with Pyrolysis Gas Flow inside in Ablator. |

21. | Experimental and numerical studies of spalled particles ejected from a light-weight ablator. |

22. | Yusuke Takahashi, Hisashi Kihara, Ken-Ichi Abe, Numerical simulation of flow fields in large-scale segmented-type arc heaters, 27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010, 2010.12, Turbulent plasma flow in large-scale arc heater such as NASA 60 MW Interaction Heating Facility was numerically investigated and the distribution of the arc-heated flow-field properties were successfully obtained.The turbulent flow-field was described by the Reynolds- Averaged Navier-Stokes equations with a multitemperature model,tightly coupled with the electric field and the radiation-field calculations. In addition,an accurate and low-cost radiation model and a low-Reynolds number two-equation turbulence model were introduced into the flowfield simulation.It was quantitatively clarified that radiation and turbulence phenomena are very important mechanisms to transfer heat and momentum from high-temperature core region to cold gas region near the wall.To validate the present numerical model,the numerical solutions were compared with the experimental data,e.g.,arc voltage,mass-averaged enthalpy,chamber pressure and heat efficiency.It was indicated that the present flow-field simulation model showed good agreement over various operating conditions of the facilities.. |

23. | Thermal Response of Light-weight Ablator under Arc-heated flow. |

24. | Visualization experiment of spallated particles ejected from a light-weight ablator. |

25. | Yusuke Takahashi, Hisashi Kihara, Ken Ichi Abe, Numerical investigation of thermochemical nonequilibrium flow field in a 20kW arc heater coupled with electric field calculation, 26th International Symposium on Rarefied Gas Dynamics, RGD26, 2009.04, Numerical simulation is carried out and the distribution of flow field properties is obtained for nonequilibrium flow in a constrictor-type 20kW arc-heated wind tunnel. In the arc heater, plasma flow is highly in nonequilibrium and arc discharge plays a critical role. The flow field is described by the Navier-Stokes equations with a multi-temperature model. The flow field equations are solved with the governing equation for the electric field being coupled. Furthermore, to validate the present numerical model, the numerical solutions are compared with the corresponding experimental data. The flow characteristics in the 20kW arc heater, e.g., the arc charge and the supersonic expansion, become clear through the present simulation. Moreover, the computed results for the arc heater indicate almost full dissociation/ ionization reactions and thermochemical equilibrium in the constrictor part, while strong nonequilibrium clearly appears in the nozzle section.. |

26. | Numerical Simulation of Chemical Nonequilibrium Flows Around a Jovian Entory Probe. |

27. | Numerical Investigation of Thermochemical Nonequilibrium Flow Field in a 20kW Arc Heater Coupled with Electric Field Calculation. |

28. | Numerical Simulation of Plasma Flows in a 20kW Arc-heated Wind Tunnel Using Multi-temperature Model. |

29. | Numerical Simulation of Thermochemical Nonequilibrium Flow in an Arc-Heated Wind Tunnel. |

30. | A Basic Study of Spallation Phenomena in Ablating Heat Shielde. |

31. | Measurements of velocity field behind a small-type wind turbine. |

32. | A Thermochemical Nonequilibrium Nozzle Flow of Arc-Heated Air. |

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