Basic question on scaling

jomunkas · June 9, 2020, 16:08

Hi,

I have a very basic question. I have a fairly small airfoil around 5 cm. To calculate it's lift and drag I am using a solver in which the characteristic length is fixed to 1. Should I calculate the Re number like:
$\rho*U*0.05/\mu$
And run simulation with this Re, which will mean that the rho,U,mu numbers will change.

Or I should run simulations with $\rho*U*1/\mu$ and then scale down the coefficients, but that means that the simulations are performed at a higher Re number then the real problem?

Kind Regards,
Jomunkas

tas38 · June 10, 2020, 10:47

Your goal should be to match the Reynolds numbers between the physical domain and the model. In this way you are striving for dynamic similitude.

June 9, 2020, 16:08	Basic question on scaling	#1
jomunkas New Member Peter Join Date: May 2019 Posts: 13 Rep Power: 7	Hi, I have a very basic question. I have a fairly small airfoil around 5 cm. To calculate it's lift and drag I am using a solver in which the characteristic length is fixed to 1. Should I calculate the Re number like: $\rhoU0.05/\mu$ And run simulation with this Re, which will mean that the rho,U,mu numbers will change. Or I should run simulations with $\rhoU1/\mu$ and then scale down the coefficients, but that means that the simulations are performed at a higher Re number then the real problem? Kind Regards, Jomunkas

June 10, 2020, 10:47		#2
tas38 Senior Member Troy Snyder Join Date: Jul 2009 Location: Akron, OH Posts: 220 Rep Power: 19	Your goal should be to match the Reynolds numbers between the physical domain and the model. In this way you are striving for dynamic similitude. jomunkas likes this.

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