Tham khảo tài liệu 'wind tunnels and experimental fluid dynamics research part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 548 Wind Tunnelsand Experimental Fluid Dynamics Research For the present qualitative analysis two dimensional computations carried out over the model symmetry plane are taken under consideration in particular the conditions Ho 35 MJ kg Po 2 bar are analyzed this condition corresponding to the lower freestream Knudsen number lử3 by comparing the results obtained with a classical Navier-Stokes approach and DSMC method in order to check possible local effects of rarefaction. Note that for tills high enthalpy case it has been decided to not perform the CFD slip computation since more accurate DSMC calculations are not strongly CPU-time demanding due to the reduced number of needed particles. Specifically this test case is characterized by the following flow properties Re m X 103 TA 240 K and a model attitude of 12 deg. A grid-independence study for CFD simulations has been carried out as well as a study of DSMC solution sensitivity to the number of particles not shown . A preliminary analysis has been carried out considering the wall at fixed temperature of 300 K and the following Fig. 13 and Fig. 14 show the Mach number contours and the streamlines for the two performed computations. Figures show the strong bow shock wave ahead of the model that is more inclined as expected in the case of DSMC simulation the strong expansion on the bottom part of the model and finally the shock wave boundary layer interaction around the corner and the subsequent recirculation bubble that is in incipient conditions in the case of rarefied flow simulation. Fig. 13. CFD Mach number contours and streamlines Evaluation of Local Effects of Transitional Knudsen Number on Shock Wave Boundary Layer Interactions 549 Fig. 14. DSMC Mach number contours and streamlines The Fig. 15 exhibits the slip velocity wall distribution predicted by DSMC calculation showing a peak value of about 1 3 of freestream velocity in correspondence of the beginning of the flat plate downstream of the .
