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Bren December 6, 2007 06:03

Divergence of trailing edge pressure?
 
Hi guys, I'm reading through a paper and the author frequently refers to the "divergence of trailing-edge pressure". I've got a rough understanding of aerodynamics but I don't know what this expression means.

If someone could please explain what it means then I'd be very grateful. Cheers, Bren

Bren December 6, 2007 07:11

clarification
 
sorry I just realised that my original question was perhaps a tad vague.

To put the expression into context:

"Pearcey shows how the trailing-edge static pressure controls the development of the steady transonic flow about a rigid airfoil and how the divergence of steady trailing-edge pressure may sometimes indicate the onset of unsteady separated flow"

Is a quote from the article. I don't understand what the author means by "divergence of steady trailing-edge pressure" - this is a physical phenomena and has nothing to do with numerical divergence.

Could someone please advise? Bren

ag December 6, 2007 13:12

Re: clarification
 
I believe that all the terminology means is that the flow field prior to separation (at onset) is very sensitive to changes in the trailing edge pressure gradient. The upstream shock wave is not strong enough to induce separation by itself, but between the shock and the trailing edge the flow is in a precarious situation. A slight disturbance causing the pressure gradient to increase is sufficient to cause a major shift in the flow field and lead to the flow separating upstream of the trailing edge. In this case it can be thought of as divergent because a very small change in dp leads to a large-scale change in the flow field.

Alex December 6, 2007 18:57

Re: clarification
 
In experimental studies of 1980s, the "divergence of trailing edge pressure" implied an abrupt increase of the pressure against the angle of attack. See a paper by Lee B.H.K. in Progress in Aerospace Sciences, Vol. 37, 2001, page 158.


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