The effect of the fluidic TED is different, the separation is not suppressed, but the rear wing loading is increased and consequently the buffet onset is not delayed to higher angles of attack, but only to higher lift coefficient.
In contrary, for the turbine with less blade number, it is possible to obtain a relatively more moderate attack angle at the high rotational speed, to allow the turbine obtaining the high lift coefficient at the high rotation speed.
The GOE478 airfoil was chosen because of the ease of measuring the lift under the non-driven condition, its relatively high lift coefficient at low Reynolds numbers, and its simple shape.
Indeed, in Fig. 10a a full separation from the leading edge is evident, as expected by the experiments, while in (b) the flow is partially attached thus resulting in higher lift coefficient values and in a delay of the stall angle.
As with the angle of attack, a high camber results in a high lift coefficient, but also in an increased drag of the wing (Anderson, 1991).
We found an increasing deflection of the leading edge with decreasing speed hence suggesting a higher lift coefficient at lower flight speeds (Fig. 8a).
With increasing flight speed the requirements for a high lift coefficient is reduced and a decrease of the camber reduces the increasing profile drag (Laitone, 1997).
A higher angle of attack produces higher lift, but also higher drag, and therefore the bats are expected to reduce the angle of attack with increasing flight speed when the demand of a high lift coefficient is reduced.
It is found that in purely two-dimensional flows, very high lift coefficients can be realized.
Compared with a conventional fin, the results show the benefits of the flapping foil with relatively higher lift coefficients and lower drag coefficients.
