Shallow water effect of tandem flapping foils on renewable energy production

Studies about the flapping foil hydrokinetics turbines, as a new method to extract energy from incoming flow field, have recently increased significantly. Studies on the effect of shallow water conditions on the performance of the turbine have not been seen so far. This study investigates the effect of working environment on the performance of flapping foil hydrokinetic turbine. The unsteady and incompressible flow around two flapping foils in tandem operate in shallow water is simulated using Computational Fluid Dynamic (CFD) method. The results of shallow water conditions are compared with deep-water case. It is observed that the shallow water condition heavily affects the performance of the system and the total efficiency decreases considerably. Particularly, when the kinematic parameters are optimum for performance, the total power extraction efficiency of the system for h(0)?=?6c, h(0)?=?3c and h(0)?=?1.5c has a reduction of 7.24, 8.5, and 10.14%, respectively, compared with deep-water case. The interaction between the boundary layer of the sea floor and the flapping foils was found to be the main factor of efficiency reduction.