Investigation of passive devices for axisymmetric base13; drag reduction at transonic speeds

Experiments have been made to assess the effectiveness of13; several base modifications for reducing base drag and total13; afterbody drag at transonic speeds. The modifications tested include base cavities, ventilated cavities and two vortex suppression devices. Results show that, while appreciable base drag reductions are possible with many of the devices examined, the net total drag reductions are lower, presumably because of the additional losses associated with the devices.