Hydrodynamic characteristics of cambered NACA0012 for flexible-wing application of a flapping-type tidal stream energy harvesting system

Investigation of phase difference and separation distance effects in the design of a dual flapping hydrofoil turbine

“…The characteristics of the front foil in case 23 that match the undulation wake differ from those of the rear foil in case 30 that matches the LEV, which is reported to exist at a higher AOA 25 . Moreover, it has been reported that the lift force decreases as the AOA increases from above an AOA of 15° from a water channel experiment of which the condition is close to the range of Reynolds numbers used in our simulation 26 . The maximum AOAs for both cases are above 15° as well; thus, the smaller force at the rear foil in case 30 is speculated to be due to vortex shedding from the front foil, which causes the AOA of the rear foil in case 30 to increase.…”

“…25 Moreover, it has been reported that the lift force decreases as the AOA increases from above an AOA of 15°from a water channel experiment of which the condition is close to the range of Reynolds numbers used in our simulation. 26 The maximum AOAs for both cases are above 15°as well; thus, the smaller force at the rear foil in case 30 is speculated to be due to vortex shedding from the front foil, which causes the AOA of the rear foil in case 30 to increase. The trends of the forces, pressure distributions, and vortex characteristics of the front foil in case 30 and of the rear foil in case 23 can be explained in the manner similar to that of the front foil for case 23 and the rear foil for case 30.…”

“…An in-house code, in this case a parallelized multiblock-structural Navier-Stokes solver, is adopted; it was validated and has been utilized in several FHTrelated studies. 8,18 To deal with the relative motion between the body-fitted mesh and the domain mesh for the FHT, the multigrid method known as the chimera method is used. Details of the chimera grid system for dual hydrofoils are shown in Figure 3.…”

“…They were able to verify the performance of the prototype using 2D CFD simultaneously 17 . Sitorus et al studied a dual system with a left‐swing trajectory for the front hydrofoil and a right‐swing trajectory for the rear hydrofoil through a CFD analysis 18 . In other studies of flapping mechanisms, Muscutt et al studied the motion of two pairs of flippers in ancient marine creatures and found that the phase difference and separation distance between the two flippers have considerable effects on the propulsion efficiency 19 .…”

“…17 Sitorus et al studied a dual system with a left-swing trajectory for the front hydrofoil and a right-swing trajectory for the rear hydrofoil through a CFD analysis. 18 In other studies of flapping mechanisms, Muscutt et al studied the motion of two pairs of flippers in ancient marine creatures and found that the phase difference and separation distance between the two flippers have considerable effects on the propulsion efficiency. 19 Ji et al suggested an optimization framework based on an active learning method to determine the conditions of tandem flapping wings for optimal performance in terms of thrust or efficiency.…”