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-   -   fluent inlet velocity setup (http://www.cfd-online.com/Forums/fluent/97533-fluent-inlet-velocity-setup.html)

linyx February 20, 2012 00:18

fluent inlet velocity setup
 
HI everybody
I have a problem running fluent, l am simulating a air flowing through a wing, since it is a low velocity problem, I do not have to think about the mach effect. In gambit, I construct the wing with a cord length of 1m, for convenient sake, and set flow velocity of 200m/s in order to maintain the Re. the inlet boundary type in velocity_inlet and outlet boundary type is pressure_outlet. is it OK to set up like this? I mean the inlet velocity is near the c, which is the sound velocity, will the flow generate the shock wave?
Hoping for answers!

federvo.mala February 20, 2012 04:55

Quote:

Originally Posted by linyx (Post 345228)
HI everybody
I have a problem running fluent, l am simulating a air flowing through a wing, since it is a low velocity problem, I do not have to think about the mach effect. In gambit, I construct the wing with a cord length of 1m, for convenient sake, and set flow velocity of 200m/s in order to maintain the Re. the inlet boundary type in velocity_inlet and outlet boundary type is pressure_outlet. is it OK to set up like this? I mean the inlet velocity is near the c, which is the sound velocity, will the flow generate the shock wave?
Hoping for answers!


You are in the transonic regime, therefore (maybe) some local supersonic areas might occur on the wing with related shock and compression waves.

I have never treated supersonic flow in Fluent so far, but I think you are going to take care of the supersonic effects in the setup. I don't know how, I think there might be a tutorial.

linyx February 22, 2012 04:23

Actually, I have simulated it in the fluent, yes, the velocity is around the transonic region, but the there seems no shock wave, and velocity contour is more or less the same to the simulation of the actually model(20m in chord, 10m/s in velocity). Do they happen to be the same, or is there any reasons behind them.

diamondx February 22, 2012 12:09

try pressure far field with your corresponding mach number...

Ali.

linyx February 23, 2012 01:05

Actually, I am simulating a low velocity problem, I just want to konw if it is ok to set the chord length 1 and corresponding inlet velocity of 200m/s, which maintains the Re number. the lift and drag are the same according to my simulation result.

Hypersonicflow February 23, 2012 12:36

Hi,

the Reynolds number might be the same, but your Mach number is not. At V=200 m/s, I estimate your Mach number is around 0.6, which is larger than 0.3. Hence, you will get additional effects of compressibitily in your surrogate "high speed" case. For maintaining the Reynolds analogy, rather increase the pressure than the speed.

Cheers, Rob


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