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March 15, 2011, 04:59 |
floatingObject in 2D or axi-symmetric
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#1 |
New Member
Jordi Muela
Join Date: Mar 2011
Posts: 27
Rep Power: 16 |
Hi everyone,
i'm trying to solve the floatingObject case (interDyMFoam solver) in 2D and 2D Axi-symmetric. I have modified de mesh, the boundary conditions and I have added the necessary constraints at the models. The problem is that i get divergence in a few time-steps because the object falls down very quickly. I'm 'playing' with the mass at patch pointDisplacement, but the body falls quickly, no matter if the mass is very high or low (differences in magnitude orders). Where is the problem? The boundary type "sixDoFRigidBodyDisplacement" only works fine in 3D models? Somebody has already implemented a similar model? Any response and helpfull will be welcome! Thank you everyone! |
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April 9, 2013, 20:48 |
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#2 | |
Senior Member
Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 845
Rep Power: 18 |
Quote:
I am facing the same problem,the box is sinking. How to handle this? |
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May 20, 2013, 06:59 |
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#3 |
New Member
QuocThien
Join Date: Apr 2013
Posts: 16
Rep Power: 13 |
hi!
I think that u need restraints the object with low factor to reduce motion and increase the relaxation factor. Maybe i'm wrong! |
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May 22, 2013, 10:47 |
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#4 |
Senior Member
Join Date: Mar 2013
Location: USA
Posts: 120
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I am having the same problem. My object is sinking very fast. I will try to restraint the object with a low factor with increasing the relaxation factor and see what happens.
Thanks for the help, |
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May 22, 2013, 19:43 |
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#5 |
Senior Member
Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 845
Rep Power: 18 |
I tried restrain it in verticalspring. looks like it can deal with the sinking . But this is not DOF. I dont know how to deal with DOF to make it normally.
http://zhan.renren.com/openfoam There is a non-newtonian fluid free surface flow |
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May 23, 2013, 12:14 |
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#6 |
Senior Member
Join Date: Mar 2013
Location: USA
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I found the problem. My "rhoInf" variable was "1000" in the "pointDisplacement" file. When I changed it into "1", my object started to float again.
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May 23, 2013, 19:28 |
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#7 |
Senior Member
Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 845
Rep Power: 18 |
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May 23, 2013, 19:39 |
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#8 |
Senior Member
Join Date: Mar 2013
Location: USA
Posts: 120
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Yes, it is 2D. But the results I am getting are weird. I don't know if it is because of "rhoInf" or there is another thing wrong somewhere else.
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May 23, 2013, 19:46 |
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#9 | |
Senior Member
Dongyue Li
Join Date: Jun 2012
Location: Beijing, China
Posts: 845
Rep Power: 18 |
Quote:
Reagrds |
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October 31, 2013, 10:15 |
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#10 |
New Member
Jorge Gadelho
Join Date: Feb 2013
Posts: 22
Rep Power: 13 |
Hello everyone,
I've made the changes has described in the first post to the floatingObject tutorial to transform it to a 2D problem. Like described, I'm facing the same problem. The object falls very fast. I've tried to change the rhoInf, but with no luck. Any news? thank you. |
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July 18, 2014, 07:11 |
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#11 |
New Member
Join Date: Aug 2013
Posts: 4
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Although this thread is now quite old, I still try to add something to the discussion.
I also modified the floatingObject tutorial and reduced the dimensionality of the problem by one by modifying the mesh and introducing appropriate 6 DoF constraints. To summarize,
Code:
type sixDoFRigidBodyDisplacement; centreOfMass (0 0 0); momentOfInertia (0.005568 0.0007893333333 0.00482133333333); mass 0.64; rhoInf 1; // needed only for solvers solving for kinematic pressure report on; value uniform (0 0 0); constraints { maxIterations 500; fixedLine1 { sixDoFRigidBodyMotionConstraint fixedLine; tolerance 1e-6; relaxationFactor 0.7; fixedLineCoeffs { refPoint $centreOfMass; direction (0 0 1); } } fixedAxis1 { sixDoFRigidBodyMotionConstraint fixedAxis; tolerance 1e-3; relaxationFactor 0.7; fixedAxisCoeffs { axis (1 0 0); } } } Code:
--> FOAM Warning : From function Time::operator++() in file db/Time/Time.C at line 982 Increased the timePrecision from 16 to 17 to distinguish between timeNames at time 0.0648223531977 #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 in "/lib64/libc.so.6" #3 void Foam::MULES::limiter<Foam::geometricOneField, Foam::zeroField, Foam::zeroField>(Foam::Field<double>&, Foam::geometricOneField const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::zeroField const&, Foam::zeroField const&, double, double, int) at ??:? #4 void Foam::MULES::limit<Foam::geometricOneField, Foam::zeroField, Foam::zeroField>(Foam::geometricOneField const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh>&, Foam::zeroField const&, Foam::zeroField const&, double, double, int, bool) at ??:? #5 Foam::MULES::explicitSolve(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh>&, double, double) at ??:? #6 at ??:? #7 __libc_start_main in "/lib64/libc.so.6" #8 at ??:? ./run.sh: Zeile 16: 45533 Gleitkomma-Ausnahme interDyMFoam P.S.: Since I think it is instructive if others can compare to their settings, I uploaded my whole case. |
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March 10, 2015, 07:37 |
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#12 |
Member
Ali
Join Date: Oct 2013
Location: St John's Canada
Posts: 31
Rep Power: 12 |
Hi,
I am trying to use waveDyMFoam (Modified according to instruction from waves2foam) to simulate 6DOF for a ship in waves at zero speed. I have run simple cases for 2D and 3D block. both cases are working fine. But when I am trying to use for ship, it is sinking very quickly. From the last time step, I found that free surface is not getting updated , it just goes downward with ship. I couldn't solve the problem for last 2 weeks. I appreciate any kind of help and suggestion. Ali |
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March 13, 2015, 07:44 |
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#13 |
New Member
Join Date: Aug 2013
Posts: 4
Rep Power: 13 |
This looks like a problem with your case setting. A bit more information would be helpful, otherwise it is difficult for us to help you. Did you check your
Code:
U Code:
type movingWallVelocity; |
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March 14, 2015, 06:35 |
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#14 |
Member
Ali
Join Date: Oct 2013
Location: St John's Canada
Posts: 31
Rep Power: 12 |
Hi MarcelK,
Thank you very much for your reply. I have checked the U boundary condition for rigid body and it is movigwallVelocity. I have correct the box property and it is not sinking now, But the force is increasing so rapidly after some times and ends with crash. Here is link of case folder. I am running the case in OF 2.3.1. I need to solve this problem within very short time. Any kind of advice is highly appreciated. Ali https://www.dropbox.com/sh/i0eg20ywb...fSJd778Ka?dl=0 |
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November 19, 2015, 15:47 |
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#15 |
New Member
Magnus
Join Date: Feb 2015
Posts: 7
Rep Power: 11 |
Hi Ashim!
This thread is abit old but did you manage to solve the problem you described in the last post? I am having a similar issue. |
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November 21, 2015, 07:10 |
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#16 |
Member
Ali
Join Date: Oct 2013
Location: St John's Canada
Posts: 31
Rep Power: 12 |
Hi Magnus,
I have solved the problem by changing the values of damping factor in dynamicMeshDict file. Just check the your object's properties and dynamicsMeshDict files carefully. Actually I moved to to foam-extend to simulate the floating body since I have to use multiple bodies in my simulation |
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January 13, 2016, 12:40 |
Free Surface goes up with object
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#17 |
Member
Gautami Erukulla
Join Date: Mar 2009
Posts: 71
Rep Power: 17 |
P { margin-bottom: 0.08in; }A:link { } Hello Ashim,
I am simulating a floating object in a 2D wave tank, using OpenFOAM 2.2.0, solver interDyMFoam. The case where the floating object is in the center of the wave tank, half immersed in water seem to work fine. Now I am trying to simulate a case where the floating object is under the water (a neutrally buoyant body ). The density of the object is taken as half the density of water. After a couple of time steps the run blows and I noticed that the free surface goes up along with the floating object (tried the same run with a high density body, the body sinks and the free surface goes down with the body). Your advise on this issue will be highly appreciated. Thank you. Most&More, Gautami Erukulla. |
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February 4, 2016, 13:44 |
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#18 | |
Member
Gautami Erukulla
Join Date: Mar 2009
Posts: 71
Rep Power: 17 |
Hello Ashim,
Please find attached my case. Thanks. Most&More Gautami Erukulla. Quote:
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September 15, 2023, 05:50 |
Free Surface moves with Object
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#19 | |
New Member
Arun Kumar
Join Date: Sep 2019
Location: Dundee, Scotland
Posts: 15
Rep Power: 7 |
Quote:
Did you happen to find a reason for why this was happening? I have an object in water that is neutrally buoyant as per my calculations but the computations always blow up after sometime with the object moving to the left and downwards, while taking the free surface with it. Please respond if you've figured a solution. Regards, Arun. |
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Tags |
2d model, axi-symmetric, floatingobject, interdymfoam |
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