A NUMERICAL STUDY OF TURBULENT SUPERSONIC ISOTHERMAL-WALL CHANNEL FLOW

A study of compressible supersonic turbulent flow in a plane channel w ith isothermal walls has been performed using direct numerical simulat ion. Mach numbers, based on the bulk velocity and sound speed at the w alls, of 1.5 and 3 are considered; Reynolds numbers, defined in terms of the centreline velocity and channel half-width, are of the order of 3000. Because of the relatively low Reynolds number, all of the relev ant scales of motion can be captured, and no subgrid-scale or turbulen ce model is needed. The isothermal boundary conditions give rise to a flow that is strongly influenced by wall-normal gradients of mean dens ity and temperature. These gradients are found to cause an enhanced st reamwise coherence of the near-wall streaks, but not to seriously inva lidate Morkovin's hypothesis: the magnitude of fluctuations of total t emperature and especially pressure are much less than their mean value s, and consequently the dominant compressibility effect is that due to mean property variations. The Van Driest transformation is found to b e very successful at both Mach numbers, and when properly scaled, stat istics are found to agree well with data from incompressible channel f low results.