CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Problem with rigidBodyMeshMotion library

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 7, 2024, 20:46
Default Problem with rigidBodyMeshMotion library
  #1
New Member
 
Adwaith Nath
Join Date: May 2021
Location: St John's, Canada
Posts: 5
Rep Power: 5
adwaith.nath is on a distinguished road
Hi,

I am trying to run a simulation for bare hull resistance for KCS using interFoam. I first ran a steady state simulation with LTS till the forces on the hull converged and then using this as the initial solution, I ran anunsteady simulation where the hull was allowed to move along the z direction and rotate about the y axis.

I was using rigidBodyMeshMotion library but I noticed that the trim was around 0.4 degrees which is incorrect.

When I use the sixDoFRigidBodyMesh library the trim is correct which is around 0.16 degrees.

Please note that all the other parameters are the same for both the cases . I have attached the both the dynamicMeshDict files along with this for reference.

When I say correct, it means I have experimental data, and simulations from both starccm and finemarine and all these show the same results which is 0.16 degree trim.

Is this a bug in the rigidBodyMeshMotion libarary or am I doing something incorrect. I checked the tutorial files DTCHullMoving and my setup is similar.

Thanks in advance.

dynamicMeshDicts.zip

sixDof_trim.png

rigidbody_trim.png

Last edited by adwaith.nath; March 7, 2024 at 22:09.
adwaith.nath is offline   Reply With Quote

Old   March 8, 2024, 11:47
Default Differences in code when compared with reference
  #2
New Member
 
Adwaith Nath
Join Date: May 2021
Location: St John's, Canada
Posts: 5
Rep Power: 5
adwaith.nath is on a distinguished road
I checked the book mentioned in the post regarding the implementation of the rigidBodyMeshMotion library:
Question on the differences of rigidBodyMotion and sixDoFRigidBodyMotion.

On comparing the pseudo code with the implementation, I noticed some differences. Could this be the source of the error? The code used transpose of the spatial transform matrix Xlambda_ instead of the inverse in a certain part of the code. (I apologize, it was not Hodge Dual but inverse. I misread the book)

I have attached the portions of the code where I noticed the discrepancy.

I wanted to add that I need to use rigidBodyMeshMotion library for the next step of project which is to simulate self-propulsion with a meshed propeller. I have already simulated self-propulsion (using AMI) integrating a PI controller to guess the rps based on the hull resistance and interestingly the simulation did not crash but the results including the trim and the rps were not correct. So, I am sure that the problem with library, if any, is not related to the transformation of the joints as if this was the case then the simulation would have crashed due to the ami surfaces not being correctly aligned. So, my best guess would be that the problem should be related to the forwardDynamics function.

Did any one else have a problem with this library?

Thanks in advance

reference.png

forwardDynamics.C.png

Last edited by adwaith.nath; March 8, 2024 at 23:38.
adwaith.nath is offline   Reply With Quote

Reply

Tags
openfoam, rigidbodymeshmotion

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Weird Problem while compiling new library ashish.vinayak OpenFOAM Programming & Development 3 March 15, 2019 11:39
Mesh& steptime independant: conduction-convection problem Fati1 Main CFD Forum 1 October 28, 2018 14:52
Problem linking library AlmostSurelyRob OpenFOAM Programming & Development 19 March 1, 2017 10:59
decomposePar is missing a library whk1992 OpenFOAM Pre-Processing 8 March 7, 2015 08:53
Strange Problem With updating the library farhagim OpenFOAM 0 August 10, 2010 13:34


All times are GMT -4. The time now is 15:32.