Design of marine propellers with prescribed and optimal spanwise circulation distributions based on genetic algorithms and neural network

Lifting-surface design methods are proposed for marine propellers based on genetic algorithms (GAs) and a two -layer back-propagation neural network (BPNN). For propellers with prescribed spanwise circulation distribu-tions, the design problem is solved as GA-based optimization of camber surface geometry and pitch distribution which produce a circulation distribution to best fit the prescribed one. An in-house code based on the vortex lattice method (VLM) is employed to simulate circulation distribution and hydrodynamic performance of the propeller. Computer codes are developed in this research based on existing genetic algorithms, with a measure devised to accelerate convergence and improve the quality of solution. To optimize the spanwise circulation distribution, GAs are utilized again to explore the BPNN model established via the MATLAB toolbox and the in-house VLM code. Then the optimal circulation distribution is taken as the prescribed one for the GA-based design method mentioned above. Numerical tests are conducted to determine proper ranges of modeling parameters, such as the population size for GAs and the number of vortex lattices, and to assess the performance of the BPNN established. To numerically validate the proposed methods, viscous-flow simulation by solving the Reynolds -averaged Navier-Stokes equations is carried out for the propeller designed by using both methods mentioned above. The predicted pressure distributions over blade surfaces correlate consistently with the circulation dis-tributions used to design the propeller, thus indicating that present design methods are effective and reasonably accurate.

Automated summary

A lifting-surface design method for marine propellers is proposed using genetic algorithms and a back-propagation neural network. The method optimizes the geometry and pitch distribution of the propeller to best fit a prescribed circulation distribution. The effectiveness and accuracy of the method are confirmed through numerical tests and viscous-flow simulations.