Unsteady internal boundary layer analysis applied to gun barrel wall heat transfer

Convective heating to gun barrel walls is of considerable importance when attempting to evaluate the degradation of performance in a ballistic device. The purpose of this study was to isolate and examine convective heating in order to calculate gun tube wall temperature as occurs during the firing of a projectile. Internal flow structure was decoupled by specifying in viscid core properties through measured and assumed axial and temporal variations. A fluid mechanics model was then used to solve the unsteady, compressible, and turbulent momentum and energy boundary layer development at discrete piston locations. Shear layer solutions were coupled through the energy equation. A consideration of radial heat conduction into the bore surface of the ballistic device was used to predict the interior wall temperature history at all locations behind a moving projectile. The results, when compared to those predictions which utilize integral methods and assumed known heat transfer coefficients, indicate that conventional integral methods do not adequately represent the convective heat transfer process. The influence of transverse curvature on the surface heating of small bore guns was examined. Recommendations are given for improving the present model.