A Computational Study of Hypersonic Flows Using Energy Relaxation Method

Suryakant Nagdewe,H. D. Kim,G. R. Shevare 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.6

Reasonable analysis of hypersonic flows requires a thstrong shock waves or high pressure and temperature states in the flow field. The energy relaxation method (ERM) has been used to model such a non-equilibrium effect which is generally expressed as a hyperbolic system of equations with a stiff relaxation source term. Relaxation time that is multiplied with source terms is responsible for non-equilibrium in the system. In the present study, a numerical analysis has been carried out with varying values of relaxa-tion time for several hypersonic flows with AUSM (advection upstream splitting method) as a numerical scheme. Vi-laxation time reduces to zero, the solution marches toward equilibrium, while it shows non-equilibrium effects, as the relaxation time increases. The present computations predicted the experiment results of hypersonic flows with good accuracy. The work carried out suggests that the present energy relaxation method can be robust for analysis of hyper-sonic flows.

Flow Field Analysis on the Stagnation Streamline of a Blunt Body

이창호 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.2

The hypersonic flow on the stagnation streamline of a blunt body is analyzed with quasi one-dimensional (1-D) Navier-Stokes equations approximated by adopting the local similarity to the two-dimensional (2-D)/axisymmetric Navier-Stokes equations. The governing equations are solved using the implicit finite volume method. The computational domain is confined from the stagnation point to the shock wave, and the shock fitting method is used to find the shock position. We propose a boundary condition at the shock, which employs the shock wave angle in the vicinity of the stagnation streamline using the shock shape correlation. As a result of numerical computation conducted for the hypersonic flow over a sphere, the proposed boundary condition is shown to improve the accuracy of the prediction of the shock standoff distance. The quasi 1-D Navier-Stokes code is efficient in computing time and is reliable for the flow analysis along the stagnation streamline and the prediction of heat flux at the stagnation point in the hypersonic blunt body flow.

지구 재돌입 시 우주왕복선 주위 유동 수치 해석

안상준,채정헌,이준우,최중근,허진영,김규홍 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.4

우주왕복선이 지구 재돌입을 할 때 발생하는 극초음속 물리 현상은 열화학적으로 비평형인 고온 유동으로 가정할 수 있다. 본 연구에서는 이러한 가정을 바탕으로 지구 재돌입하는 우주왕복선의 극초음속유동을 해석하였다. 전산해석에 사용된 비평형 코드는 two-temperature 모델과 11 화학종의 화학반응을 고려하였다. 공간차분에는 AUSM+의 수치진동 문제를 해결한 AUSMPW+ 기법을 사용하였고, 시간적분과 제한자는 각각 LU-SGS 기법과 MLP 기법을 적용하였다. 전산해석 결과 우주왕복선 하단부에서 강한 충격파와 고온 고압의 유동이 나타났다. 이로 인하여 산소와 질소의 해리가 발생하는 것을 확인할 수 있었다. Hypersonic physical phenomena occur when the Space Shuttle re-entry to the Earth, it can be assumed as the high-temperature and non-equilibrium flow. Based on these assumptions, in the present study, we analyzed the hypersonic flow of the Space Shuttle re-entry to Earth. Non-equilibrium code that was used in the computational analysis, should be considered the chemical reaction of 11-species and two-temperature model. To the spatial difference, we use AUSMPW + scheme that solves the problem of numerical oscillations of AUSM +, a time integer and limiter, we applied the method LU-SGS and MLP, respectively. Computerized analysis, high-temperature, high-pressure flow and strong shock wave became clear from the bottom of the Space Shuttle. This allows oxygen and nitrogen occurs disassociation.

Flow Field Analysis on the Stagnation Streamline of a Blunt Body

Lee, Chang-Ho The Korean Society for Aeronautical and Space Scie 2016 International Journal of Aeronautical and Space Sc Vol.17 No.2

The hypersonic flow on the stagnation streamline of a blunt body is analyzed with quasi one-dimensional (1-D) Navier-Stokes equations approximated by adopting the local similarity to the two-dimensional (2-D)/axisymmetric Navier-Stokes equations. The governing equations are solved using the implicit finite volume method. The computational domain is confined from the stagnation point to the shock wave, and the shock fitting method is used to find the shock position. We propose a boundary condition at the shock, which employs the shock wave angle in the vicinity of the stagnation streamline using the shock shape correlation. As a result of numerical computation conducted for the hypersonic flow over a sphere, the proposed boundary condition is shown to improve the accuracy of the prediction of the shock standoff distance. The quasi 1-D Navier-Stokes code is efficient in computing time and is reliable for the flow analysis along the stagnation streamline and the prediction of heat flux at the stagnation point in the hypersonic blunt body flow.

극초음속 유동에서의 표면 촉매 재결합

김익현(Ikhyun Kim),양요셉(Yosheph Yang) 강원대학교 산업기술연구소 2023 産業技術硏究 Vol.43 No.1

This paper provides a general overview of surface catalytic recombination in hypersonic flow. The surface catalytic recombination phenomena is elaborated in terms of its general overview and numerical modeling associated with it. The general overview of the surface catalytic recombination phenomena describes the elementary surface reactions for the surface catalytic and the role of the surface catalytic recombination efficiency in the heat transfer determination. In the numerical modeling, the surface catalytic recombination is described based on the stagnation-point boundary layer analysis, and finite-rate surface reaction modeling. Throughout this overview manuscript, a general understanding of this phenomena is obtained and can be used as foundation for deeper application with the numerical computational fluid dynamics (CFD) flow solver to estimate the surface heat transfer in the hypersonic vehicles.

Flow Field Analysis on the Stagnation Streamline of a Blunt Body

Chang-Ho Lee 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.2

The hypersonic flow on the stagnation streamline of a blunt body is analyzed with quasi one-dimensional (1-D) Navier-Stokes equations approximated by adopting the local similarity to the two-dimensional (2-D)/axisymmetric Navier-Stokes equations. The governing equations are solved using the implicit finite volume method. The computational domain is confined from the stagnation point to the shock wave, and the shock fitting method is used to find the shock position. We propose a boundary condition at the shock, which employs the shock wave angle in the vicinity of the stagnation streamline using the shock shape correlation. As a result of numerical computation conducted for the hypersonic flow over a sphere, the proposed boundary condition is shown to improve the accuracy of the prediction of the shock standoff distance. The quasi 1-D Navier-Stokes code is efficient in computing time and is reliable for the flow analysis along the stagnation streamline and the prediction of heat flux at the stagnation point in the hypersonic blunt body flow.

마하 7 극초음속 충격파 터널에서 항력 감소를 위한 플라즈마 제트 발생 장치 연구

이재청(Jae Cheong Lee),이유석(Yu Seok Lee),이형진(Hyoung Jin Lee),허환일(Hwanil Huh) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.11

초음속/극초음속 비행체의 선두부에서 발생하는 충격파에 의한 항력을 줄이기 위해 역분사 유동에 대한 연구가 시도되고 있다. 본 연구에서는 플라즈마 제트를 분사하기 위해 DC 플라즈마 발생 장치를 제작하고 기초 실험을 수행했다. 고속 유동은 마하 7 극초음속 충격파 터널에서 모사되며, 해당 유동 조건에서 플라즈마가 방전될 수 있는 요구 조건을 분석했다. 질소, 아르곤, 헬륨 가스를 이용한 방전성능 시험을 거쳐 마하 7 극초음속 충격파 터널에서 질소 플라즈마 제트를 분사하여 실험하였다. 실험결과, 마하수 7 극초음속 유동에서 분사 전압력에 따라 플라즈마 역분사 제트가 분사됨을 확인했다. Counterflow jets have been used in an attempt to reduce the drag caused by the shock wave in front of a supersonic/hypersonic vehicle. In this study, a direct-current plasma generator was designed and fabricated to inject plasma jets and fundamental experiments were performed. To simulate high-speed flow, a Mach 7 hypersonic shock tunnel was used and the requirements for plasma discharge under high-speed flow conditions were analyzed. After discharge performance tests using N₂, Ar, and He gas, the N₂ plasma jets were injected and tested in the Mach 7 hypersonic shock tunnel. The results show that counterflow plasma jets were injected according to injection pressures in Mach 7 hypersonic flow.

가상풍동 개발을 위한 극초음속 유동 해석 및 검증

채정헌,이준우,안상준,김규홍 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

현재 국방과학연구소와 한국과학기술정보연구원의 주도하에 ‘가상 현실을 이용한 가상풍동 개발’이 연구 중에 있다. 가상풍동 연구 개발은 크게 격자생성, 전산해석 그리고 가시화로 이루어져 있으며, 전산해석 분야에 있어서는 아음속, 천음속, 초음속 그리고 극초음속 해석 기법의 연구 및 검증으로 이루어져 있다. 본 연구에서는 극초음속 해석 기법을 가상풍동에 성공적으로 적용하기 위해 가상풍동 환경에서 극초음속 유동 해석 코드의 검증을 수행하였다. 가상풍동 환경에서 극초음속 유동 해석 코드의 검증을 위하여 3차원 난류 평판 해석과 받음각이 있는 3차원 로켓 형상의 해석을 수행하였고, 이를 참고문헌의 이론값과 풍동시험 결과와 비교하여 검증하였다. Led by Agency for Degense Development (ADD) and Korea Institute of Science and Technology Information (KISTI), a study of the development of virtual wind tunnel in virtual reality is being conducted. The development of virtual wind tunnel consists of grid generation, numerical analysis and visualization processes. Numerical analysis on the virtual wind tunnel requires to develop analysis method of subsonic, transonic, supersonic and hypersonic flow. In this study, we apply computing code of hypersonic fluid dynamics analysis to virtual wind tunnel. For this verification, we compare the results of 3D turbulence flow on plate and flow on rocket model with theory and results of wind tunnel test.

Aero-optical effects in the hypersonic flow field

Shi, Ketian,Miao, Wenbo,Li, Pengfei,Chen, Xiaoli The Society for Aerospace System Engineering 2015 International Journal of Aerospace System Engineer Vol.2 No.1

Aero-optical effects induced by the flow around the optical window degrade the performance of the IR seeker, especially for the hypersonic flow. For the thermochemical non-equilibrium flow, index of refraction model and optical transmission calculation method are developed to predict the aero-optical effects. The optical distortion is discussed for the typical optical widow shape and flow condition. The influence on aero-optical effects is analyzed.

Numerical Simulation of Hypersonic Viscous Flows Using an Improved Gas-Kinetic BGK Scheme on Unstructured Meshes

T.H. Yang,O.J. Kwon 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.10

This paper concerns the development of a gas-kinetic flow solver on unstructured meshes in the study of two-dimensional continuum and transitional flows. The gas-kinetic BGK scheme is based on numerical solutions of the BGK simplification of the Boltzmann transport equation. In the initial reconstruction, the unstructured version of the linear interpolation is applied to compute left and right states along a cell interface. In the gas evolution step, a modified discretization of distribution functions is adopted to improve the convergence characteristics for viscous flows. The numerical transports for mass, momentum, and energy are computed from the evaluation of the time-dependent gas distribution function around a cell interface. Two-dimensional hypersonic viscous simulations have been conducted to verify the performances of the current kinetic solver for flows considered into transitional regime. The computed results show fair agreement with other standard particle-based approaches for both continuum part and transitional part.