The effect of vortex generators on the hydrodynamic performance of a submarine at a high angle of attack using a multi-objective optimization and computational fluid dynamics

Abstract

Having a suitable maneuverability is of a high importance in the design of submarines. They should have a proper stability during depth changes and emergency rise which requires patterns in their design. In present study, the optimal design of nature inspired Vortex Generators (VGs) attached to the leading edge of side rudders of DARPA sub-off submarine is studied considering an emergency rise condition. To understand the effect of ideal design of VGs on hydrodynamic performance of the submarine, Computational Fluid Dynamics (CFD) analysis are coupled with Multi-Objective Genetic Algorithm (MOGA). To perform the CFD-based optimizations at angle of attack equal to 30°, 4 input parameters based on geometry and positioning of VGs are considered and the drag and lift coefficients of submarine are set as the objective functions. The results of CFD simulations and the optimization shows that VGs optimal geometry have the properties of L = 0.021315 (m), α = 90°, t = 0.00625 (m) and d = 0.027 (m) which results in the CD and CL of submarine being equal to 0.081005 and 0.058114, respectively. Application of VGs causes an small increase in CD in comparison with main model due to enlargement of stagnation point at the leading-edge. VGs also divide the fluid-flow into two portions, both of which experience an enhancement in their turbulent kinetic energy at the leading-edge. Finally, a sensitivity analysis demonstrates the range of applicability of VGs for all the depth changes.