Scale effect and undersea noise of counter-rotating propellers installed in tidal stream power unit

Abstract

More attentions are paid to the renewable energies in face of global warming and depletion of fossil fuel. Tidal energy as one of the renewable energies has fruitful advantages as predictable and sustainable resources. The authors have proposed a counter-rotating type tidal stream power unit and investigated preliminarily the effect of the Reynolds number on the output, namely scale effect, and undersea noise of the counter-rotating propellers. The hydraulic loss increases at the low Reynolds number with accompanying the boundary layer separation. The noise has the dominant frequencies corresponding to the blade passing frequencies in counter-rotating propellers.