# Reynolds Number matching in Cavity flow

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 December 17, 2005, 06:48 Reynolds Number matching in Cavity flow #1 Endee Guest   Posts: n/a Hi, I was going through one of the test cases in cavity flows throuhg M219 cavity. ( www.qnet-cfd.net/workshop/3rd/pdf/ws3-03.pdf ). Test conditions are Mach number 0.85, Characteristic length 20 inches (length of cavity) and Reynolds number of 6.84e6. Temperature,density or pressure is not explicity stated. For this case we have the experimental windtunnel data available as well which I assume will have been on standard pressure and temperature conditions??. How to match the Reynolds number for given 20 in characteristic length and Mach no 0.85? As if I take STP (rho=1.225 kg/m3, velocity=295.11 m/s, length=20in=0.508m, meu=1.7894e-5, gives Re=10.263e6 which is greater than the test condition). I tried to vary the temperatures from 0-30 c but couldnot find any combination of rho,vel and meu to have the test reynolds no. Any suggestion is welcome. Endee

 December 18, 2005, 06:26 Re: Reynolds Number matching in Cavity flow #2 ztdep Guest   Posts: n/a i think you must give how your RE is defined.

 December 19, 2005, 05:09 Re: Reynolds Number matching in Cavity flow #3 Endee Guest   Posts: n/a Reynolds number is based on the length of cavity and Mach nymber 0.85. No temperature, density or pressure is specified. But with in a realistic range of temperature 0-40 degree celcius, the corresponding velocity at Mach 0.85, characteristic length (20 in =.508 m) and molecular viscosity (meu) does not give that Reynolds number. It is rather more than that. Thanks

 December 19, 2005, 05:21 Re: Reynolds Number matching in Cavity flow #4 Lionel Larchevêque Guest   Posts: n/a Hi, As far I as remember, QinetiQ experimental data on M219 cavity flows include operating conditions such as stagnation pressure and temperature. For my computations on this case I was using a U_\infinity=276.45 m.s^-1 resulting in a Reynolds number of about 7 millions. Best regards.

 December 19, 2005, 05:46 Re: Reynolds Number matching in Cavity flow #5 Lionel Larchevêque Guest   Posts: n/a Hi, Complementary to the previous message. The stagnation pressure and temperature I've used can be found somewhere in the following article : Larcheveque, Sagaut, Le and Comte, JFM 516, pp 265-301, 2004. Sorry, presently I have no copy of the article left to check the exact values. However I've managed to find a file containing the operating conditions for the experiments (in imperial units). If you're interested, just send me an email. Regards, Lionel

 January 2, 2006, 11:34 Re: Reynolds Number matching in Cavity flow #6 morteza yosefi Guest   Posts: n/a i am mechanical engineer. please send thise file for me. thanks.

April 20, 2010, 04:47
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Quote:
 Originally Posted by Lionel Larchevêque ;39416 Hi, As far I as remember, QinetiQ experimental data on M219 cavity flows include operating conditions such as stagnation pressure and temperature. For my computations on this case I was using a U_\infinity=276.45 m.s^-1 resulting in a Reynolds number of about 7 millions. Best regards.
lionel,i read your paper~Large-eddy simulation of a compressible ﬂow in a three-dimensional open cavity at high Reynolds number~have you obtained any data about the heat on the wall of the cavity, thanks