CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

Definition of propulsive efficiency

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   February 10, 2007, 23:59
Default Definition of propulsive efficiency
Posts: n/a

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

  Reply With Quote

Old   February 11, 2007, 00:13
Default Re: Definition of propulsive efficiency
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.
  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
OpenFOAM static build on Cray XT5 asaijo OpenFOAM Installation 9 April 6, 2011 12:21
Efficiency, thrust/drag with regard to hovering quarkz Main CFD Forum 0 April 21, 2010 00:51
Parelleling Efficiency kassiotis OpenFOAM 0 June 19, 2009 14:12
Efficiency for hovering flight? Zonexo Main CFD Forum 1 April 14, 2008 00:49
Negative propulsive efficiency of a moving airfoil zonexo Main CFD Forum 4 March 7, 2007 01:16

All times are GMT -4. The time now is 14:16.