Quasi-Steady Aerodynamic Characteristics Of Terminal Sensitive Bullets With Short Cylindrical Portion

The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets (TSB) with low aspect ratio, especially in terminal trajectory. Currently, there is little research in terms of the TSB and short cylinder with two free ends, and particularly in this trajectory, where the scanning angle beta and roll angle alpha vary over a broad range between 0 degrees and 180 degrees. In this work, wind tunnel experiments are first conducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters for short cylinder with aspect ratio L/D = 1. Similar to infinite cylinder, for the short cylinder with two free ends, the drag crisis phenomenon still exists in the critical regime 1.7 x 10(5) <= Re <= 6.8 x 10(5). Then 3D simulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSB over a broad range of Re, L/D, alpha and beta. The sensitivity analysis of time step and grid are presented as well. When beta = 0 degrees, for short cylinder, the drag crisis phenomenon was also observed in the simulation, but not as obvious as in the wind tunnel test. In some attitudes, there is an obvious Karman vortex in the wake of short cylinder and TSB. The correlation between time-averaged aerodynamic coefficients and L/D, Re, alpha &beta is discussed. The vortex shedding frequency and shear layer behavior are obtained for quasi-steady and unsteady flow. Finally, the effect of end's shape on drag reduction and vortex shedding frequency is analyzed.