Role of synthetic jet control in energy harvesting capability of a semi-active flapping airfoil

The role of synthetic jet (Sj) control in the energy harvesting capability of a semi-active flapping airfoil is numerically investigated in this study. An elliptic airfoil with ratio of 8, which is placed in a two-dimensional laminar flow, is employed to harvest energy from the flow field. The airfoil undergoes an imposed pitching motion, and then an induced plunging motion can be achieved. A pair of SJs with the same frequency and strength is integrated into the upper and lower surfaces of flapping airfoil. As a result, the flow field around the airfoil would be modified by the SJs. At the Reynolds number of 1100 and the pitching axis location of one-third chord, the effects of the inclined angle between the jet direction and the chord line, the phase angle between the SJs and the pitching motion as well as the position of Si slot on the energy harvesting capability are systematically examined. With the help of SJs, it is demonstrated that the enhancement of energy harvesting efficiency can be achieved. Based on the numerical analysis, it is indicated that the jet flow on the airfoil surfaces with suitable working parameters, which results in the obvious increase of lift force, can benefit the energy extraction performance of the flapping airfoil. (C) 2020 Elsevier Ltd. All rights reserved.