Shaping of Axisymmetric Bodies for Minimum Drag in Incompressible Flow

A method is presented for the automatic synthesis of minimum drag hull shapes for axisymmetric vehicles of specified enclosed volume and constant speed submerged in incompressible, nonseparat-ing, noncavitating flow at zero incidence. The computer-oriented optimization procedure does not consider propulsion or maneuvering; drag reduction is accomplished solely through manipulation of the vehicle hull shape. The selected optimization formulation is a nongradient algorithm in a finite, constrained parameter space. This study considers an eight-parameter class of rounded-nose tail-boom bodies constrained to be well behaved as determined by previous hydrodynamic experience. The drag model, for nonseparating flows at zero incidence, is based on classical hydrodynamics and consists of computer programs from work available in the literature; the model is representative of state-of-the-art drag prediction methods. By exploiting laminar flow while avoiding turbulent sepa-ration, a body with a drag coefficient one-third below the best existing laminar design has been ob-tained. The evidence suggests that the method produces realistic hull shapes useful in engineering design. The optimization procedure is independent of any particular drag model so that the effects on minimum drag shapes due to alternate drag models can be studied. Nomenclatur