Transition Characteristics of Flowfield in a Simulated Solid-Rocket Motor

Abstract

The e ow characteristics in a two-dimensional porous-walled duct simulating a solid-propellant rocket motor are numerically computed to investigate the effects of viscosity, compressibility, and ine ow turbulence ( w) on the e ow transitions. The e nite volume technique is used to solve the time-dependent compressible Navier‐ Stokes equations with a subgrid-scale turbulence model, and the numerical e uxes are computed using a modie ed Godunov scheme. In addition to computed axial mean velocity and turbulence intensity proe les, the axial variations of skin friction coefe cient and the transverse location of peak turbulence intensity are used to identify the mean-e ow transition and turbulence-intensity transition, respectively. In particular, a new way of identifying turbulence-intensity transition by the use of the power spectrum of velocity e uctuations is presented for the e rst time in the present study. The minimum centerline Mach number for the onset of mean-e ow transition is obtained as the compressibility is considered alone. The critical values of w for the onset of turbulence-intensity transition and mean-velocity transition advance as well as for the concurrence and delay between the two transitions are also determined to illustrate why some researchers could observe only a single transition whereas others observed two transitions.