Sphere Drag in Solid Rockets—Non-Continuum and Turbulence Effects

Abstract

An experimental study relating to the momentum transfer between the gas and condensed phase in metallized solid propellant rocket motors has been conducted. Non-continuum and turbulence effects on sphere drag have been measured in a small, vertical, subsonic wind tunnel incorporating a magnetic suspension system. Drag data have been obtained at Reynolds numbers (Re) ranging from 40 to 5000, Mach numbers (Af) of from 0.10 to 0.57, Knudsen numbers (Kn) as high as 0.060, and turbulence intensities up to 13 %

Sphere drag measurements taken with moderate (0.4 to 3.3 %) levels of turbulence show that turbulence of these levels produces significant drag increases for Reynolds numbers between 200 and 800. The data indicate that, for a given turbulence level, the percentage drag rise due to turbulence decreases with decreasing Re; the C_D increase approaches zero for Re  100.

For sphere drag data obtained at turbulence levels of from 3 to 13% and Reynolds numbers of from 600 to 5000, a very pronounced effect of sphere diameter is evident. At a given Re, C_D increases monotonically with inverse sphere diameter. Present data for 40  Re  200 and 0.17  M  0.57 exhibit pronounced noncontinuum and compressibility effects. These data are compared with empirical relations and other experimental data found in the literature.