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 J. McCarthur October 26, 1999 12:18

Strouhal Frequency

Guys,

Does anybody know how to calculate the Strouhal Frequency for a highly turned (about 90 degrees) turbine blade? I know how to do that for cylinder, for thin airfoil, but not for such a high turning turbine blade. thanks.

J.M.

 Md. Ziaul Islam October 26, 1999 13:07

Re: Strouhal Frequency

I have done similar kind of calculations to visualize incylinder fluid phenomena using similarity principles. The analysis also involve calculations using other numbers such as Euler Number, Reynold's Number and some other parameters. But for turbine blade, I heard of a number called Dean Number can be used for calculations. Results are obtained at Dean Number from 50 to 1100 which include laminar channel flow, laminar flow with Dean vortex pairs, flow with secondary instabilities, channel flow with local regions of augmented turbulence, and turbulent channel flows.

 Rainer Kurz October 26, 1999 15:52

Re: Strouhal Frequency

I assume that you're looking for the Strouhal number associated with the von Karman vortices in the wake of the turbine blade. For a turbine blade, this Strouhal number depends mainly on the Reynoldsnumber and the Mach number. I'm not aware of any simple equation, but I vaguely remember that for many subsonic flow regimes and Reynoldsnumbers above 1000 , the Strouhal number is between 0.2 and 0.3, if the trailing edge thickness is used as the lenghth dimension.

 Md. Ziaul Islam October 26, 1999 16:18

Re: Strouhal Frequency

Do you know anything about Dean Number? If you know then we would really appreciate if you would please explain to us in a simple manner. Thank you.

 Gabor BALINT October 31, 1999 09:51

Re: Strouhal Frequency

See

Robert D. Blevins: Flow Induced Vibration, 1977, van Nostrand

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