Experimental simulation of the flows in front of and behind a projectile with and without gas slippage

The interior ballistic flows in front of and behind a projectile were simulated in a high pressure shock tube. The projectile was accelerated by shock reflection in a rectangular barrel equipped with windows. The flow pattern was visualized with a differential interferometer. The heat flux into the barrel wall was measured with thin film platinum gages. In the flow pictures no influence of gas leakage on the flow pattern behind the projectile was observed. However, the flow in front of the projectile was strongly affected. The heat flux measurements show that in the presence of a gas leakage a heat flux into the wall of the barrel occurs in front of the projectile. The heat flux attains a maximum level in the slit between wall and projectile; this leads to high temperature gradients producing high thermal stresses in the barrel wall.