低レイノルズ数圧縮性チャネル乱流の乱流統計量の無次元パラメータ依存性 : 第1報,平均流れ場と乱れの統計量(流体工学,流体機械)

The dependence of mean flow and turbulence statistics on the non-dimensional parameters, the Mach number and the Reynolds number, is investigated using direct numerical simulation (DNS) of the low-Reynolds number compressible turbulent channel flow between isothermal walls. The Mach number M is based on the bulk velocity and sound speed at the wall. The Reynolds number Re is based on the bulk density, bulk velocity, channel half-width, and viscosity at the wall. Five computational cases are considered. The computational cases of Re=2000 with M=1.0, 1.25 and 1.5 are Cases A, B and C, respectively. The computational cases of M=1.5 with Re=2 000, 2500 and 3000 are Cases C, D and E, respectively. The main results of this report are as follows : (1) As M increases, the semi-local friction Reynolds number based on the local density and viscosity, semi-local friction velocity, channel half-width becomes larger in y*l3 and smaller in y*g3, where y* is the semi-local wall unit. (2) The mean dilatation profile depends on Re and M, even if the variable property effect is taken into account. (3) The region where the compressibility affects on the near-wall asymptotic behavior of wall-normal velocity intensity becomes wider with the increase of M and the decrease of Re.