Direct numerical simulations of subsonic plane Poiseuille flows undergoingtransition

Compressible Navier-Stokes equations are numerically solved to study spatia lly developing plane Poiseuille flows undergoing transition to turbulence. Navier-Stokes Characteristic Boundary Conditions and Compact Finite Differe nce Scheme are used in the streamwise (x) and the vertical (y) directions, however a classical Fourier method is employed in the periodic (z) directio n. Several subsonic simulations, with isothermal walls, for different Mach numbers and forced with different random-disturbances are carried out to st udy the effects of compressibility and disturbances on the transition mecha nism. Some of the simulations in their early transitional state, (i.e. DNS of Re = 2 500 and M = 0.5 plane Poiseuille flow perturbed at the inlet with 5% of the streamwise velocity amplitude) show the appearance of omega (y) vorticity component in the vicinity of the walls. This near wall vertical v orticity along with the generated streaks, located between the counter rota ting vortices, evolve downstream with a longitudinal elongation.