S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Mechanical Aerospace Engineering (기계항공공학부) Theses (Master's Degree_기계항공공학부)
Comparison of upper boundary conditions for RANS used in wall-modeled large eddy simulation
벽 모델 큰 에디 모사에서의 RANS 상단 경계 조건 비교
- 공과대학 기계항공공학부
- Issue Date
- 서울대학교 대학원
- Large eddy simulations; Wall modeling; Wall shear stress; Turbulent flows; Numerical modeling
- 학위논문 (석사)-- 서울대학교 대학원 공과대학 기계항공공학부, 2017. 8. 최해천.
- The hybrid RANS/LES using zonal approach with wall shear stress model is one of the wall-modeled large eddy simulation (WMLES) techniques developed to reduce computation cost in high Reynolds number flow simulations. In this approach, how to exchange flow field information between solutions from a wall model and LES through the boundary conditions is one of the important issues. In general, the wall boundary condition of LES is given as the instantaneous wall shear stress obtained in the wall model RANS, whereas the upper boundary condition for RANS is provided as the instantaneous velocity component acquired from the solution of LES. However, it does not guarantee an accurate estimation of wall shear stress due to a resolved portion of turbulent shear stresses in RANS. In this study, a new WMLES is suggested which is directly imposing the instantaneous total shear stress obtained in LES as the upper boundary condition for RANS, rather than velocity component and assessed in turbulent channel and boundary layer flows. It is shown that the present WMLES based on the total shear stress boundary condition predicted the logarithmic velocity profile and the low-order turbulence statistics at high Reynolds numbers even with very coarse grid resolution.