Surrogate-model-based drag reduction of a SUBOFF model using blowing and suction

Abstract: Reducing the drag and noise of high-speed underwater vehicles is important for ocean exploration and the ocean economy. This work develops an active control technology to reduce the drag of underwater vehicles at high Reynolds number (Re - 10^7). Reynolds-averaged Navier-Stokes equations, closed with a turbulence model of realizable k-ε two-layer, are used to investigate the drag reduction (DR) of a bare SUBOFF model by blowing and suction. Three arrays of steady blowing/suction jets through annular slots are deployed, incorporating 5, 5, and 10 slots, respectively, and have been shown to yield significant DR. Meanwhile, net-energy-saving rate (S), defined as the change rate of net saved energy after subtracting the input energy for active control from the energy saved from DR, can be achieved. Combined control of 15 parameters from two effective arrays of blowing jets achieves a maximum DR of 23.2%, but with a negative S of -7.1%, when performing surrogate-model-based optimization. An efficient control is discovered with a maximum S of 3.8% and DR = 8.0%. The innovatively modified surrogate model is shown to quickly find optimal solutions. Keywords: Underwater vehicle, active drag reduction, numerical simulation, steady blowing/suction