Effect of Base Bleed on Drag of a Boat-Tail Projectile

Abstract

A numerical study has been carried out on a boat-tail base bleed projectile of 63.5 mm body diameter and 7◦ boat-tail angle at Mach number 2.46 to understand the effect of base bleed, by varying injection parameter from 0.00 to 0.0226. An axisymmetric, compressible, density based mass average Navier-Stoke equations are solved using realizable non-equilibrium wall function k−ε turbulent model. The k−ε equations are solved using the implicit algorithm and second order upwind for flow and first order upwind for turbulent kinetic energy and dissipation rate. The base pressure was calculated for all five injection parameter and the results obtained through present study shows that maximum base pressure occurs earlier for boat-tail base bleed configuration at injection parameter equal to 0.0113. The primary recirculation zone was completely removed at injection parameter equal to 0.0148 and the maximum value of base pressure ratio is 0.74 which is 12 higher compared to blunt base with the base bleed projectile. A considerable reduction in skin friction coefficient has also been observed especially at boat-tail and the base section. Variation in bleed area of the projectile was done to see the pressure variation and then plotted it against different injection parameter. For all area, the same trend has been observed except when bleed ejected from the complete base.