## Fluids

#### Set Reynolds and Mach number

• Andrea159357
Subscriber

Hello, i'm trying to validate an experimental test on an airfoil on fluent. I don't know how to set up Reynolds and Mach number. I've got Re = 460000 and Ma = 0.13 while the total pressure is 15 psi. Can someone help me?

• raul.raghav
Subscriber

So you don't have an input for Reynold number or Mach number in Fluent. You can calculate the velocity based on your Reynolds number of 460,000. Since your Mach number is 0.13, you can use an incompressible fluid to solve the problem. And what location is the total pressure measured?

And when you say "I've got Re = 460000 and Ma = 0.13 while the total pressure is 15 psi", do you mean you got them the experimental test?

• Andrea159357
Subscriber

Thanks Raul for your answer. Yes I've got them on experimental test. I suppose total pressure was measured in the center of the wind tunnel so it's like p-infinity. I know my problem is incompressible but i read that a better simulation is always compressible, is that true?

I've already calculate free stream velocity supposing air density (rho=1.225), Temperature (T = 15°C) and dynamic viscosity (mu=1,78 10^-5)  but i don't know how to set boundary contition. I set inlet, outlet and pressure far-field on a C-type mesh so a can set mach number on the far field.

Another question is: should i scale my airfoil (0.14 m) like the tested one or can i let it 1 m chord length? If i use the incompressible solver i can use Reynolds to find a different velocity fit for 1 m chord length (6.68 m/s). Instead, if a use compressible one, i use Mach and i find the velocity (44,69 m/s) used in experimental test. Considering 1 m chord length, Reynolds number should increase a lot, Should i consider this problem or not?