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yin May 9, 2000 23:01

stall
 
Hi! I don't know if this is the right place to ask the question. but anyway, I'm a little confused on the term stall on airfoil flow, some books categorize stall as Leading Edge stall, Trailing Edge Stall and Thin Airfoil Stall, while some other (in journal papers usually, without exactly defining the terms) use the term Static and Dynamic stall. I undetstand the first 3 terms, but am not sure of the latter two. I've tried searching through aerodynamic books but none have used these terms. Could anyone help me out. Thanks in advance.

-yin-

Tim Franke May 10, 2000 04:03

Re: stall
 
Hi,

static stall means the decay of lift of an airfoil having exceeded a certain angle of attack. In this case the airfoil is in rest. If that airfoil executes a pitching motion (mostly oscillatory), stall occurs delayed (at higher aoa) compared with the static case and so you get higher max lift coefficents. The lift for the downstroke motion is on a lower level because of delayed reattachement of the flow. So there's a hysteresis in lift (in drag and moment coefficient as well). This is a typical characteristic of dynamc stall. Dynamic stall is a phenomen which occurs e.g. at helicopter rotor blades or wind turbines.

Hope this helps,

Tim



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