DIRECT NUMERICAL-SIMULATION OF HYPERSONIC BOUNDARY-LAYER FLOW ON A FLARED CONE

The forced transition of the boundary layer on an axisymmetric flared cone in Mach 6 flow is simulated by the method of spatial direct numer ical simulation (DNS). The full effects of the flared afterbody are in corporated into the governing equations and boundary conditions; these effects include nonzero streamwise surface curvature, adverse streamw ise pressure gradient,and decreasing boundary-layer edge Mach number. Transition is precipitated by periodic forcing at the computational in flow boundary with perturbations derived from parabolized stability eq uation (PSE) methodology and based, in part, on frequency spectra avai lable from physical experiments. Significant qualitative differences a re shown to exist between the present results and those obtained previ ously for a cone without afterbody Bare. In both cases, the primary in stability is of second-mode type; however, frequencies are much higher for the Bared cone because of the decrease in boundary-layer thicknes s in the flared region. Moreover, Goertler modes, which are linearly s table for the straight cone, are unstable in regions of concave body f lare. Reynolds stresses, which peak near the critical layer for the st raight cone, exhibit peaks close to the wall for the flared cone. The cumulative effect appears to be that transition onset is shifted upstr eam for the Bared cone. However, the length of the transition zone map possibly be greater because of the seemingly more gradual nature of t he transition process on the flared cone.