Confusion about non-dimensionalization and Reynolds no.

quarkz · June 20, 2011, 10:40

Hi,

I am confused about non-dimensionalization and Reynolds no.

I have a numerical NS solver which uses the non-dimensional NS equation to solve.

I can specify the Re and u_inf values.

Supposed I want to solve the flow past a cylinder.

I let Re = 40, u_inf = 1. I get a steady solution of cd=1.6

If I now change u_inf to 2, my cd becomes around 5.

However, Re is still 40. I thought that if my Re remains the same, I should get the same ans...

Did I miss out something? Or is there something wrong with my solver?

Hope someone can help!

morteza08 · June 20, 2011, 15:26

respected friend
I think you are trying to slove a problem that you have not the sufficient knowledge about that.
Non-dimensionalization is one the fundamental course matters in fluid mechanics...
Take a look at some fluid mechanics to get more familiar with this matter.
Explain more about the code...
I can help you........

quarkz · June 20, 2011, 18:11

Hi, I think there's something wrong with my numerical solver.

I tried to run the same case in Fluent. As long as the calculated Re=40, my result will be the same. I can double the velocity from 1 to 2. In that case, to get the same Re, I can maybe half the density. The ans for both will be the same.

June 20, 2011, 10:40	Confusion about non-dimensionalization and Reynolds no.	#1
quarkz Senior Member TWB Join Date: Mar 2009 Posts: 400 Rep Power: 19	Hi, I am confused about non-dimensionalization and Reynolds no. I have a numerical NS solver which uses the non-dimensional NS equation to solve. I can specify the Re and u_inf values. Supposed I want to solve the flow past a cylinder. I let Re = 40, u_inf = 1. I get a steady solution of cd=1.6 If I now change u_inf to 2, my cd becomes around 5. However, Re is still 40. I thought that if my Re remains the same, I should get the same ans... Did I miss out something? Or is there something wrong with my solver? Hope someone can help!

June 20, 2011, 15:26		#2
morteza08 Senior Member Morteza Join Date: May 2010 Location: Iran,Islamic Republic of Posts: 161 Rep Power: 15	respected friend I think you are trying to slove a problem that you have not the sufficient knowledge about that. Non-dimensionalization is one the fundamental course matters in fluid mechanics... Take a look at some fluid mechanics to get more familiar with this matter. Explain more about the code... I can help you........

June 20, 2011, 18:11		#3
quarkz Senior Member TWB Join Date: Mar 2009 Posts: 400 Rep Power: 19	Hi, I think there's something wrong with my numerical solver. I tried to run the same case in Fluent. As long as the calculated Re=40, my result will be the same. I can double the velocity from 1 to 2. In that case, to get the same Re, I can maybe half the density. The ans for both will be the same.