Menu

Discussion Forum

New Discussion
查找

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Damping Factor too small

Posted 2010年4月15日 GMT-4 08:44 5 Replies

Arun Thomas
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam


Hi

I am trying to simulate the wind flow past a cylinder of dimension 0.00084m as radius and with density 1.23 and viscosity as 1.85e-5. Using the property of similutde when i scaled down to this dimensions given above,but then my velocity has to be 500m/s.

When I solve using SPOOLES as the solver. I got the errror " Damping Factor too Small.Returned solution has not converged". I am not so familiar with these terms.But if I run with a lower velocity like 1m/s I get a good solution.

Can we use comsol only to small parameter problems.

Please let me know what can be done to solve this problem.

Best Regards

Thomas
5 Replies Last Post 2010年4月16日 GMT-4 08:14
Danial Tz
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2010年4月15日 GMT-4 10:16
What is the Reynolds number (with respect to the diameter of the cylinder) you are trying to achieve?

If it is higher than 1000-2000 you will need special treatments with nearly everything in Comsol.
What is the Reynolds number (with respect to the diameter of the cylinder) you are trying to achieve? If it is higher than 1000-2000 you will need special treatments with nearly everything in Comsol.
Arun Thomas
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2010年4月15日 GMT-4 10:51
Hi Danial

Thank you for replying to my problem.

My dimensions are diamter of cylinder 0.168m with 5 m/s velocity ,density of air 1.23 and viscosity of 1.85e-5.

So when i calulate it Reynolds number its realy very high, arounf 56,000. Does that mean I cannot solve this problem?

Thanks for helping.

Best Regards
Thomas

Hi Danial Thank you for replying to my problem. My dimensions are diamter of cylinder 0.168m with 5 m/s velocity ,density of air 1.23 and viscosity of 1.85e-5. So when i calulate it Reynolds number its realy very high, arounf 56,000. Does that mean I cannot solve this problem? Thanks for helping. Best Regards Thomas
Danial Tz
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2010年4月15日 GMT-4 11:22
I do not have an answer to whether it is possible or not.

You should take care of turbulence, either using Turbulent models inside the Comsol, i.e. k-e model if you want to just simulate the general flow behaviour. Otherwise if you want to resolve the eddies and vortices behind the cylinder, I am not sure if you can do it with the methods available in Comsol. In that case I can imagine you go with methods like LES to resolve the eddies at high Re's.

I do not have an answer to whether it is possible or not. You should take care of turbulence, either using Turbulent models inside the Comsol, i.e. k-e model if you want to just simulate the general flow behaviour. Otherwise if you want to resolve the eddies and vortices behind the cylinder, I am not sure if you can do it with the methods available in Comsol. In that case I can imagine you go with methods like LES to resolve the eddies at high Re's.
Arun Thomas
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2010年4月16日 GMT-4 07:57

Hey Daniel

Thanks for the tip.It worked!

I just wanted to simulate the flow past a cylinder.Now I got great simulation with turbulences.
Hey Daniel Thanks for the tip.It worked! I just wanted to simulate the flow past a cylinder.Now I got great simulation with turbulences.
Danial Tz
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2010年4月16日 GMT-4 08:14
great to hear it works!
great to hear it works!

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content