Henry McDonald

On the use of k-epsilon turbulence model for computation of solid rocket internal flows

The internal flow in a solid propellant rocket motor cold-flow model has been simulated via numerical solution of the ensemble-averaged Navier-Stokes equations and a modified k-r turbulence model. The modifications incorporated in the turbulence model utilize the ratio of the wall injection velocity to the friction velocity as a relevant similarity parameter in characterizing the relative dominance of the injection effects over the boundary layer effects. This parameter is used in evaluating the turbulence kinetic energy and length scale at the porous surface. Furthermore, the low Reynolds number terms in the k-r turbulence model are also modified using this parameter. The modified turbulence model has been used with a linearized block-implicit code to simulate the internal flow in a nozzleless solid rocket cold-flow model. The computed results have been compared with the experimentally measured axial velocity, turbulence intensity, Mach number and pressure profiles.

Calculation of three-dimensional turbulent subsonic flows in transition ducts

A method for computing three-dimensional turbulent subsonic flow in curved ducts is being developed. A set of tube-like surface oriented coordinates is employed for a general class of geometries applicable to subsonic diffusers with offset bends. The geometric formulation is complex and no previous treatment of this class of viscous flow problems is known to the authors. The duct centerline is a space curve specified by piecewise polynomials. A Frenet frame is located on the centerline at each axial location. The cross sections are described by super-ellipses imbedded in the Frenet frame. Duct surfaces are also coordinate surfaces, which greatly simplifies the boundary conditions. The resulting coordinates are nonorthogonal.