Laminar-to-turbulent transitions over an ablating reentry capsule

The aerodynamic mechanism of early transition phenomena over an ablating re entry capsule has been analytically examined. A two-equation turbulence mod el (k-epsilon model) was coupled with Reynolds averaged Navier-Stokes equat ions. Low-Reynolds-number effects on the solid wall were taken into account by modifying the Chien's correction. As a result, transition occurred at t he lower Reynolds number with higher ablation rate. The predicted transitio n-point Reynolds number was 3 x 10(4) at the surface-mass-injection rate of 100 g/sm(2). The principal mechanism of this early transition is thought a s follows; the viscosity damping effects are reduced and re-laminarization is prevented in the downstream of the capsule surface, due to the turbulenc e on the surface and due to the pushing out of near-surface stream-lines fr om the surface by successive mass injection. (C) 2000 Elsevier Science Ltd. All rights reserved