|
[Sponsors] |
![]() |
![]() |
#1 |
New Member
Abdel Rhman Al-Tawil
Join Date: Nov 2017
Posts: 1
Rep Power: 0 ![]() |
I'm trying to simulate remotely controlled underwater vehicle "ROV" to get the coefficient of drag, lift force, drag force. however, I'm experiencing instability in the residual plot " especially in the continuity and k, omega" it starts stable until it reach 6e-3 then is start constant fluctuating around the value. I have tired to adjust under-relaxation factors no improvement.
here is model information Analysis 1-steady fluid flow 2-turblent flow Mesh info and Quality meshing method tetrahedral patch independent 1- orthogonal quality rang from 0.30 to 0.99 "most of the elements above 0.70" 2-Aspect Ratio rang from 1.18 to 7.18 "most of the elements below 3" 3-skewness rang from 0 to 0.78 "most of the elements below 0.60" 4- Maximum Conner Angle rang from 71.56 to 152.60 "most of the elements below 112.5" Fluent Model setup 1-k-omega SST 2-Fluid liquid water 3-Boundary Conditions inlet " velocity 1 m/s", outlet " pressure 0 pa" no pressure difference, Wall "ROV", Symmetry "rest of the planes to eliminate no slip conditions" 4-reference values specified 5- solution methods simple my residual plot look something like this Last edited by abdelrhmanaltawil; November 26, 2017 at 13:55. |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Member
Join Date: Jun 2017
Posts: 55
Rep Power: 11 ![]() |
Hi, I'm still learning CFD so I may not be able to help a lot but try to change your pressure-velocity coupling. For steady fluid flow, try using SIMPLE or SIMPLEC. These are iterative schemes used to adjust the pressure field to ensure continuity as the pressure field can't be obtained directly (with the exception of using the "Coupled" pressure-velocity coupling scheme, which is computationally expensive).
https://www.afs.enea.it/project/nept...ple-vs-simplec Check out the differences between SIMPLE and SIMPLEC in this link. Depending on your situation, you can choose between SIMPLE and SIMPLEC. Hope this helps |
|
![]() |
![]() |
![]() |
Tags |
ansys, drag coefficient, fluctuating residuals, fluent |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
Segmentation fault when using reactingFOAM for Fluids | Tommy Floessner | OpenFOAM Running, Solving & CFD | 4 | April 22, 2018 12:30 |
chtMultiRegionSimpleFoam turbulent case | Aditya Patil | OpenFOAM Running, Solving & CFD | 6 | April 24, 2017 22:13 |
simpleFoam error - "Floating point exception" | mbcx4jc2 | OpenFOAM Running, Solving & CFD | 12 | August 4, 2015 02:20 |
calculation stops after few time steps | sivakumar | OpenFOAM Running, Solving & CFD | 7 | March 17, 2013 06:37 |
Orifice Plate with a fully developed flow - Problems with convergence | jonmec | OpenFOAM Running, Solving & CFD | 3 | July 28, 2011 05:24 |