Drag Predictions for Projectiles at Transonic and Supersonic Speeds

The breakdown of the total drag into its individual components (pressure drag, viscous drag, and base drag) is important in the preliminary design stage of shell. Design codes are available to predict the individual drag components and thus, the total drag. Typically, the total drag predicted by these design codes agrees well with the total drag measured from flight tests. But, how well do these codes predict the individual drag components? Experimental verification of the prediction of the drag components is an extremely difficult task. Thus a Navier-Stokes computational procedure is used in this report to predict the individual drag components and test the accuracy of the predictions of the design codes. A thin-layer Navier-Stokes code has been used to compute the entire flow field over projectiles including the base region. Numerical calculations have been made for various Mach numbers in the transonic and supersonic regimes. Pressure drag, skin friction drag, base drag and thus, the total drag are obtained from the computed results. Comparison of drag has been made with available experimental data and also with predictions from design codes employing semi-empirical techniques.