Boundary-Layer Transition on a Hypersonic Forebody:Experiments and Calculations

摘要

The natural laminar–turbulent transition of the flow under a hypersonic forebody is investigated, bothnexperimentally and numerically. Experiments are conducted on a 1 3-scale model, in the T-313 conventionalnblowdown wind tunnel of the Institute of Theoretical and Applied Mechanics–Russian Academy of Science atnNovosibirsk, atMach numbers 4 and 6. The transition is detected frompitot pressuremeasurements in the boundarynlayer. Transition onset occurs very near the nose at Mach 4 and is delayed to the middle part of the forebody atnMach 6. For the stability analysis, the mean flow is obtained from Navier–Stokes calculations for the wind-tunnelnconditions.The localmodal linear stability theory, coupledwith the eN method, is applied in a three-dimensional fullyncompressible formulation. At Mach 4, transition is due to a traveling crossflow instability, and a weak oblique firstnmode coexists independently. At Mach 6, the crossflow instability turns progressively to a first mode. N-factors atntransition are around five.