# Definition of propulsive efficiency

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 February 10, 2007, 23:59 Definition of propulsive efficiency #1 zonexo Guest   Posts: n/a Hi, I'm trying to find out how to obtain propulsive efficiency, n for a pitching, heaving and sweeping airfoil. From some references, I managed to get these formulas: n = power input / power output ( p(out) / p(in) ) p(out) = thrust (T) * u velocity p(in) = -Lift (L)(t)*dh/dt - Moment (M)(t)*d(theta)/dt There's something which I don't understand. h in dh/dt in the reference is given as the heaving height. If there is sweeping (moving the airfoil in the x-direction) involved, will the definition change? Given the point of pitching, how should the moment be calculated? Is it given by M = L*x-T*y where x,y are the horizontal and vertical distance of the airfoil's CG from the point of pitching respectively? Thank you

 February 11, 2007, 00:13 Re: Definition of propulsive efficiency #2 zonexo Guest   Posts: n/a Oh ya, do I need to modify for a case which includes sweeping to become p(in) = -Lift (L)(t)*dh(y)/dt - Moment (M)(t)*d(theta)/dt - Thrust (T)(t)*dh(x)/dt where h(x) is the horizontal sweeping displacement and h(y) is the vertical one.

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