Influence of lengthways spacing and phase difference on traveling wave energy absorption characteristics of flexible airfoils in a diamond array

Abstract

Under certain motion parameters, traveling wave motion can absorb energy from incoming flow. In addition to the geometric and motion parameters of each unit, the arrangement also has a great influence on the energy absorption efficiency of traveling wave bodies. Using NACA0012 airfoil as a two-dimensional simplified model, the influence of lengthways spacing and phase difference on energy absorption efficiency of airfoils in the diamond array is studied by numerical calculation in this paper. The results show that with the increase of the lengthways spacing between the midstream airfoils and the downstream airfoil, the transverse interference between the airfoils decreases gradually until disappear. Specifically, with the increase of lengthways spacing, the energy absorption efficiency of the midstream airfoils decreases first and then stays constant, while the downstream airfoil shows a simple harmonic fluctuation with decreasing amplitude. When there exists transverse interference in the array, the energy absorption efficiency of the midstream and downstream airfoils shows a simple harmonic fluctuation concerning the phase difference between the upstream airfoil and the downstream airfoil. When there is no transverse interference in the array, the energy absorption efficiency of the downstream airfoil is a simple harmonic fluctuation concerning the phase difference between the upstream airfoil and the downstream airfoil. Under the optimal arrangement, the energy absorption efficiency of the diamond array is 35% higher than that of a single traveling wave airfoil.