fluent inlet velocity setup

linyx · February 19, 2012, 23:18

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, 03:55

Quote:

Originally Posted by linyx

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, 03:23

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, 11:09

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

Ali.

linyx · February 23, 2012, 00:05

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, 11:36

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

February 19, 2012, 23:18	fluent inlet velocity setup	#1
linyx Member Linyx Join Date: Mar 2011 Posts: 31 Rep Power: 15	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!

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February 22, 2012, 03:23		#3
linyx Member Linyx Join Date: Mar 2011 Posts: 31 Rep Power: 15	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.

February 22, 2012, 11:09		#4
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 28	try pressure far field with your corresponding mach number... Ali.

February 23, 2012, 00:05		#5
linyx Member Linyx Join Date: Mar 2011 Posts: 31 Rep Power: 15	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.

February 23, 2012, 11:36		#6
Hypersonicflow New Member Robert Join Date: Apr 2011 Posts: 7 Rep Power: 15	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