Torque in CFD-Post

beyonder1 · September 23, 2015, 06:11

Hi,
I have went through many threads regarding this, so i hope i am not repeating.
I calculated torque about an co-ordinate system using 'torque_z_C1()@airfoil3'. The value that i obtained is 1000 order less than what i am getting experimentally. I want to calculate pitching moment of airfoil.

1. Am i am supposed to multiply something to torque value?
2. Will that torque expression mentioned give pitching moment of unit(N-m).
Please suggest anything.

Opaque · September 23, 2015, 16:01

What units are being shown in the software ?

What units are you expecting ?

beyonder1 · September 23, 2015, 16:36

It is showing [J] which is N-m which i am expecting.
But magnitude of torque i am getting is quite low. I checked my pressure values but they are good. I don't know why this is happening.

JuPa · September 23, 2015, 17:55

Have a look at the axis at which torque is calculated. In CFD Post go into calculators and calculate the torque value about the correct axis.

Antanas · September 23, 2015, 22:51

Quote:

Originally Posted by shubham2941

Hi,
I have went through many threads regarding this, so i hope i am not repeating.
I calculated torque about an co-ordinate system using 'torque_z_C1()@airfoil3'. The value that i obtained is 1000 order less than what i am getting experimentally. I want to calculate pitching moment of airfoil.

1. Am i am supposed to multiply something to torque value?
2. Will that torque expression mentioned give pitching moment of unit(N-m).
Please suggest anything.

What about the area of your airfoil? Is it the same as in your experiment?

beyonder1 · September 24, 2015, 00:57

I think you are right. I don't know how i missed this aspect. There is significant difference in both areas. Thank you for your suggestion.

One thing i am thinking is to normalize torque values with their areas. Is it correct to do this and then compare the values?

Antanas · September 24, 2015, 04:36

Quote:

Originally Posted by shubham2941

I think you are right. I don't know how i missed this aspect. There is significant difference in both areas. Thank you for your suggestion.

One thing i am thinking is to normalize torque values with their areas. Is it correct to do this and then compare the values?

Of course if areas are different then forces are also different and to compare results you should multiply them by areas ratio.

September 23, 2015, 06:11	Torque in CFD-Post	#1
beyonder1 Member beyonder Join Date: May 2015 Posts: 67 Rep Power: 10	Hi, I have went through many threads regarding this, so i hope i am not repeating. I calculated torque about an co-ordinate system using 'torque_z_C1()@airfoil3'. The value that i obtained is 1000 order less than what i am getting experimentally. I want to calculate pitching moment of airfoil. 1. Am i am supposed to multiply something to torque value? 2. Will that torque expression mentioned give pitching moment of unit(N-m). Please suggest anything.

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September 23, 2015, 16:01		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,803 Rep Power: 32	What units are being shown in the software ? What units are you expecting ?

September 23, 2015, 16:36		#3
beyonder1 Member beyonder Join Date: May 2015 Posts: 67 Rep Power: 10	It is showing [J] which is N-m which i am expecting. But magnitude of torque i am getting is quite low. I checked my pressure values but they are good. I don't know why this is happening.

September 23, 2015, 17:55		#4
JuPa Senior Member Mr CFD Join Date: Jun 2012 Location: Britain Posts: 361 Rep Power: 14	Have a look at the axis at which torque is calculated. In CFD Post go into calculators and calculate the torque value about the correct axis.

September 24, 2015, 00:57		#6
beyonder1 Member beyonder Join Date: May 2015 Posts: 67 Rep Power: 10	I think you are right. I don't know how i missed this aspect. There is significant difference in both areas. Thank you for your suggestion. One thing i am thinking is to normalize torque values with their areas. Is it correct to do this and then compare the values?