Hydrodynamic Shape Optimization of an Autonomous Underwater Vehicle With an Integrated Lifting Line and Viscous Continuous Adjoint Approach

The designs of the optimal shape of an autonomous underwater vehicle (AUV) and its aft propeller's optimal circulation can interact with each other. We propose an optimization approach that integrates the lifting line theory and the continuous adjoint method to address this conflict. The optimal circulation of a propeller is obtained via lifting line theory. The corresponding propeller force is introduced into the Reynolds-averaged flow equations as a source term and is considered in the development of a continuous adjoint formulation for the AUV shape optimization. Adjoint equations, with boundary conditions and sensitivity derivative expressions for the drag reduction problem, are derived in detail. The shapes of a small AUV and its aft propeller are simultaneously optimized using the proposed approach. Numerical results show that the proposed method decrease AUV drag by 17% at a rated speed. And a prototype test further confirms the effectiveness of the method.