The Near-Field Flow and Drag on Cylindrical Bodies Moving Concentrically Inside Very Long Tubes.

A differential simulation based on the k-model of turbulence describing the flow field around a streamlined body traveling through f1uid along the centerline of a closed end tube has been used to predict drag coefficients for a range of Reynolds numbers and diameter ratios. The range of interest corresponds to torpedotube combinations of interest to the U.S. Navy. Pressure coefficients are also plotted as a function of axial position along the body. A finite difference solution of the inviscid flow field is also developed and presented. Comparison of inviscid pressure coefficients with viscous pressure coefficients reveals that the nose region displays essentially inviscid behavior. The viscous differential model verified the hypothesis that total drag on the body could be found by independent calculation of nose drag, cylindrical section drag and wake drag, proving that nose drag and tail drag are independent of the length of the cylindrical section. A one dimensional control volume analysis was performed to predict drag coefficients as a function of Reynolds number.