Use of synthetic jet to a fully-active flapping foil for power extraction enhancement

Abstract

The power extraction performance of a fully-active flapping foil with synthetic jet is numerically investigated in this work. An elliptic airfoil with ratio of 8, which is placed in a two-dimensional laminar flow, is adopted to extract power from the flow. The foil implements the imposed translational and rotational motions synchronously. A pair of synthetic jets with the same frequency and strength is integrated into the upper and lower surfaces of flapping foil. As a result, the flow field around the foil could be affected by the synthetic jets greatly. At the Reynolds number of 1000 and the pitching axis location of half chord, the effects of the jet strength, the inclined angle between the jet direction and the chord line, as well as the phase angle between the synthetic jets and the flapping motion on the power extraction performance are systematically investigated. Compared with the traditional flapping foil, it is demonstrated that the enhancement of power extraction efficiency can be achieved with the help of synthetic jets. Based on the numerical analysis, it is indicated that the jet flow on the foil surfaces alters the vortex-shedding process and modifies the pressure distribution on the foil surface. As a result, the overall power extraction of the flapping foil can be benefitted.

Numerical simulations of biological flows and their engineering applications

“…In the field of energy harvesting, Li et al. 14 study the enhancement of power extraction efficiency of a flapping foil by using the concept of synthetic jets.…”

“…Regarding numerical tools used, there are seven papers using immersed boundary methods, 5,7,11,13–15,18 nine papers using body-fitted mesh methods 6,8–10,12,16,17,19,21 and two papers using other methods. 20,22 Among the applications involving moving boundaries, there are seven papers using immersed boundary methods, 5,7,11,13–15,18 one paper using an open source finite element software Elmer, 6 and three papers using commercial software Ansys/Fluent, 8–10,12 indicating that the immersed boundary method is an emerging alternative in solving flows involving moving boundaries and fluid-structure interaction (see also a recent review paper 23 ).…”