Flow through a submerged nozzle

Abstract

Measurements of mean and fluctuating velocity components are obtained with refractive-index-matching laser velocimetry in a submerged nozzle representative of thrust-vectoring nozzles in solid rocket motors. The approaching flow has a structure similar to that approaching a sudden contraction, but is affected by the large annular recirculation bubble that fills the outer annular cavity around the nozzle and reattaches on the nozzle lip. Turbulence production is increased, with large fluctuations in the shear layer bounding the recirculation bubble and core flow. Immediately upstream of the nozzle; this production is balanced by relaminarization processes associated with acceleration of core flow into the nozzle. The development of the wall flow inside the nozzle is significantly different from that in a simple nozzle, and the present measurements provide benchmark data that give insight into turbulence modeling assumptions used in procedures to design solid rocket motors. Nomenclature D = diameter of the upstream duct, mm d = diameter of the nozzle at the throat, mm n = refractive index R = local radius from the centerline to the wall, mm Re = Reynolds number r = radial position (origin on the centerline), mm T = temperature, K U, V = mean components of axial and radial velocity, m/s u,v = fluctuating components of axial and radial velocity, m/s x = axial position (origin in the plane of the nozzle tip), mm v = dynamic viscosity, m2/s p = density, kg/m3