Cl and Cd values very high

Phizz82 · August 9, 2013, 15:42

Hi there.

I have managed to run my aerofoil simulation but I am getting very high values of Cd and Cl. I anticipated that there may be a bit of a problem with no modelling as a compressible flow (I used the SimpleFoam solver) but not to this extent!

I have attached the my project folder if anyone can help.

Thanks

immortality · August 10, 2013, 14:53

Hi
send necessary files to me so that see if can do something:
force.of.love@gmail.com

Phizz82 · August 10, 2013, 15:04

Thanks immortality. Which filed would you need? I would guess posy processing, controldic and the whole of the 0 folder?

immortality · August 10, 2013, 15:09

Hi
0 folder constant and system if you want me run it otherwise whatever you know may the problem be there.

immortality · August 10, 2013, 16:03

why you have set rhoInf 1000? is the environment water?
but you have:
transportModel Newtonian;

rho rho [ 1 -3 0 0 0 0 0 ] 0.42;

nu nu [ 0 2 -1 0 0 0 0 ] 1.47e-05;

Phizz82 · August 10, 2013, 16:06

The environment is air at approx 11km. I have been trying to build this up from tutorials without knowing everything behind it and must have missed that. Would my rhoInf be 0.42 too or is there an equation that determines another value for it?

immortality · August 10, 2013, 16:12

yes it would be .42
correct it a look at other files carefully.run it and I have a look if another problem occurred.

Phizz82 · August 10, 2013, 16:16

>.< silly me.. of course all the values ...inf are freestream aren't they. No wonder my values were so high as only the area what a true representation. So it takes the forcecoeffs actually pulls out a lift,drag, moment values and then divides them by 1/2 rho v^2 s. I think I see where I was going wrong. Thank you very much.

Phizz82 · August 10, 2013, 16:17

Values are now in the 0.02 area for drag which seems a lot better!

immortality · August 11, 2013, 02:41

then it has been resolved?
I'm glad.what about Cl?
Send me your new settings.I want to have a look into it.

somFoam · June 30, 2015, 04:01

P { margin-bottom: 0.08in; } Hi,
I was working on OpenFoam 2.3.1. Simulated some turbulence model with komega sst for flow past Circular Cylinder Re=100000, Cd=1.12, but always getting very high cl, rms =1.
Please suggest, if there is any trick.

immortality · June 30, 2015, 05:38

is your grid fine enough near the wall of the cylinder to include viscous layer?

somFoam · June 30, 2015, 06:02

I am using wallfunction, finess is such that, yplus value varying from 18 to 310, with average 172.

somFoam · June 30, 2015, 06:06

please help, I have attached my case above.

August 9, 2013, 15:42	Cl and Cd values very high	#1
Phizz82 New Member Philip Brown Join Date: Jun 2013 Posts: 25 Rep Power: 12	Hi there. I have managed to run my aerofoil simulation but I am getting very high values of Cd and Cl. I anticipated that there may be a bit of a problem with no modelling as a compressible flow (I used the SimpleFoam solver) but not to this extent! I have attached the my project folder if anyone can help. Thanks

August 10, 2013, 14:53		#2
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	Hi send necessary files to me so that see if can do something: force.of.love@gmail.com __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

August 10, 2013, 15:09		#4
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	Hi 0 folder constant and system if you want me run it otherwise whatever you know may the problem be there. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

August 10, 2013, 16:03		#5
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	why you have set rhoInf 1000? is the environment water? but you have: transportModel Newtonian; rho rho [ 1 -3 0 0 0 0 0 ] 0.42; nu nu [ 0 2 -1 0 0 0 0 ] 1.47e-05; __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

August 10, 2013, 16:12		#7
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	yes it would be .42 correct it a look at other files carefully.run it and I have a look if another problem occurred. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

August 10, 2013, 15:04		#3
Phizz82 New Member Philip Brown Join Date: Jun 2013 Posts: 25 Rep Power: 12	Thanks immortality. Which filed would you need? I would guess posy processing, controldic and the whole of the 0 folder?

August 10, 2013, 16:06		#6
Phizz82 New Member Philip Brown Join Date: Jun 2013 Posts: 25 Rep Power: 12	The environment is air at approx 11km. I have been trying to build this up from tutorials without knowing everything behind it and must have missed that. Would my rhoInf be 0.42 too or is there an equation that determines another value for it?

August 10, 2013, 16:16		#8
Phizz82 New Member Philip Brown Join Date: Jun 2013 Posts: 25 Rep Power: 12	>.< silly me.. of course all the values ...inf are freestream aren't they. No wonder my values were so high as only the area what a true representation. So it takes the forcecoeffs actually pulls out a lift,drag, moment values and then divides them by 1/2 rho v^2 s. I think I see where I was going wrong. Thank you very much.

August 10, 2013, 16:17		#9
Phizz82 New Member Philip Brown Join Date: Jun 2013 Posts: 25 Rep Power: 12	Values are now in the 0.02 area for drag which seems a lot better!

August 11, 2013, 02:41		#10
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	then it has been resolved? I'm glad.what about Cl? Send me your new settings.I want to have a look into it. __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

June 30, 2015, 04:01	Very high Cl	#11
somFoam New Member Somsankar Mondal Join Date: Dec 2014 Posts: 4 Rep Power: 11	P { margin-bottom: 0.08in; } Hi, I was working on OpenFoam 2.3.1. Simulated some turbulence model with komega sst for flow past Circular Cylinder Re=100000, Cd=1.12, but always getting very high cl, rms =1. Please suggest, if there is any trick.

June 30, 2015, 05:38		#12
immortality Senior Member Ehsan Join Date: Oct 2012 Location: Iran Posts: 2,208 Rep Power: 26	is your grid fine enough near the wall of the cylinder to include viscous layer? __________________ Injustice Anywhere is a Threat for Justice Everywhere.Martin Luther King. To Be or Not To Be,Thats the Question! The Only Stupid Question Is the One that Goes Unasked.

June 30, 2015, 06:06	High Cl value	#14
somFoam New Member Somsankar Mondal Join Date: Dec 2014 Posts: 4 Rep Power: 11	please help, I have attached my case above.