Cd too large

rgs36 · August 13, 2012, 14:43

Hi all

I'm fairly new to CFD, and I have a problem with obtaining a drag coefficient. I know that one should be wary when using the drag coefficient from CFD, but I wanted to obtain a value for it anyway just out of interest. However, the solution seems to be converging with a Cd of 55000, which is obviously at least 5 orders out. Also, look at a total pressure plot for the model, the flow does not appear to even separate.

Has anyone had this problem before, or know what I might be doing wrong? I displayed the drag coeff plot by clicking on monitors, and showing Cd for my model (not the walls of the box surrounding it).

Many thanks

Richard

joseph@CFD · August 13, 2012, 16:56

Hi Richard,

I am currently working on low Re airfoil simulation ......so Could you pls let us know with what data you are comparing your results and what type of airfoil are you using and is your simulation 2D or 3D ?

dsking · August 13, 2012, 18:09

check the values you have under "Reference Values"

Fluent uses these to compute the drag coefficient

August 13, 2012, 14:43	Cd too large	#1
rgs36 New Member Richard Stephens Join Date: Aug 2012 Posts: 1 Rep Power: 0	Hi all I'm fairly new to CFD, and I have a problem with obtaining a drag coefficient. I know that one should be wary when using the drag coefficient from CFD, but I wanted to obtain a value for it anyway just out of interest. However, the solution seems to be converging with a Cd of 55000, which is obviously at least 5 orders out. Also, look at a total pressure plot for the model, the flow does not appear to even separate. Has anyone had this problem before, or know what I might be doing wrong? I displayed the drag coeff plot by clicking on monitors, and showing Cd for my model (not the walls of the box surrounding it). Many thanks Richard Last edited by rgs36; August 13, 2012 at 15:11.

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August 13, 2012, 16:56		#2
joseph@CFD New Member Jos Join Date: Jun 2012 Posts: 5 Rep Power: 13	Hi Richard, I am currently working on low Re airfoil simulation ......so Could you pls let us know with what data you are comparing your results and what type of airfoil are you using and is your simulation 2D or 3D ?

August 13, 2012, 18:09		#3
dsking New Member dking Join Date: Aug 2012 Posts: 12 Rep Power: 13	check the values you have under "Reference Values" Fluent uses these to compute the drag coefficient