Reynolds number for simulating with different domain lengths
 

HI.....

I am simulating following flow conditions for air flowing over a flat plate (L=2m):
rho_inf = 1.2 kg/m3
u_inf = 300 m/s
T_inf = 300 k; (viscosity comes out to be = 1.8*10^-5)
Reynolds number this case is Re = rho*u*L/viscosity = 4x10^7.

In simulating above conditions, what Reynolds number should i take for

1)for a domain length of L = 4
2)for a domain length of L = 1

Basically, the aim of question is for flow over large lengths (which are difficult to simulate), we scale down the length in simulations. How the Re will change for different cases?

I'm not sure I understand your question. First, why would you scale your model? Second, your Re usually depends on the characteristic length of your body, noton your domain…

If you want to scale your model....you need to maintain Re same over all scales....and the velocities will change accordingly (we do this for pipe flows....i guess you can use it here as well...please check)....calculate Re using L=2 and use it for other two cases...so velocities will change if you keep air as fluid...

Thankyou for your suggessions...it was helpful.