|March 28, 2013, 11:27||
High residual for extruder mesh
Join Date: Jan 2013
Posts: 75Rep Power: 4
My problem is a cylinder oscillating(swaying) on free surface. I am comparing the horizontal force from star ccm+ with experimental values.
I am have tried to use 3 different motions to simulate the same problem. The motions used were translation(overset), morphing and rigid body(overset). My inital cell size was about 5.7 lacs. I got a good agreement with experimental and CFD values. I had used trimmer for all the 3 cases.
Now i was trying to simulate the same problem with just about 50-70k cells and using morpher. In this case i used extruder mesh. I had used fine cells even at areas(the first time) far away from the cylinder. Increasing the sizes of these cells helped me to decrease the total cell count.
When i run this mesh using morpher, i am facing a problem with residual levels. I do understand residuals are not the final say for a solution to have converged. When i check the horizontal force, it is again similar to my previous results, agreeing well with the experiments. I have attached the screen shot of the force, residuals and my mesh.
1. The residuals settle to a high value but they remain constant there.The solution is not diverging i guess. I believe this is because the cells far away from the domain have a very high aspect ratio and hence there is something going wrong with the numerical calculation in those cells. How do i ascertain this in STAR CCM+? Is it possible to plot individual cell residual for me to see if they are high in the cells which are of interest to me? Ya and when i simulated it previously i was getting residuals of order of 10^-5(the first time for all 3 motions).
2. How should i improve my mesh to get a lower value of residuals?
There is no flow, cylinder is on calm water and i have wall boundary all around.
Please guide if you know the answer
|Thread||Thread Starter||Forum||Replies||Last Post|
|Velocity blows up suddenly after 30,000+ iterations||lordvon||OpenFOAM Running, Solving & CFD||15||October 19, 2015 13:52|
|pimpleFoam: turbulence->correct(); is not executed when using residualControl||hfs||OpenFOAM Running, Solving & CFD||3||October 29, 2013 09:35|
|calculation stops after few time steps||sivakumar||OpenFOAM Running, Solving & CFD||7||March 17, 2013 07:37|
|Floating point exception error||Alan||OpenFOAM Running, Solving & CFD||10||April 6, 2012 14:02|
|lift and drag on ship superstructures||vaina74||OpenFOAM Running, Solving & CFD||3||June 8, 2010 12:30|