Transonic Pressure Distribution and Boundary Layer Characteristics of a Projectile with an Asymmetric Afterbody

摘要

Measurements of pressure distribution and boundary layer characteristics were obtained on an asymmetric boattail projectile. Such configurations are being studied as potential alternatives to conventional boattails because of their reduced variation in moments in the transonic speed range. Wind tunnel tests were performed in the NASA Langley Research Center 8' Transonic Pressure Tunnel on a 5.8 caliber model with a triangular, conical and cylindrical afterbody. Integration of the pressure distribution data showed that the contribution of the triangular afterbody to the total drag is fifty percent of that of a conical configuration. Base drag and forebody drag for the triangular afterbody are assumed the same as for the conical boattail if the base areas are the same in the two cases. Integration of the moments of the pressure distribution permit the evaluation of the pitching moment configuration of the different afterbodies. The moments due to the triangular afterbody contribute relatively little to the overall pitching moment as compared to the strongly destabilizing effect of the conical boattail and the stbilizing effect of a cylindrical afterbody. Because of the asymmetric configuration the moments created depend on the orientation of the afterbody.