CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > NUMECA

Strange Results in FineMarine

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 23, 2020, 05:55
Default Strange Results in FineMarine
  #1
New Member
 
Stefano Siciliano
Join Date: Jun 2020
Posts: 1
Rep Power: 0
StefanoSic is on a distinguished road
Good day,

I am fairly new to FineMarine and have still got a few hiccups in some of the computations I have been running.

I had completed a set of computations for a 35m vessel and realised that the viscous layers were not added correctly, so I went to change that and started having issues with the solver crashing.

I believed it to be a mesh quality issue and so I refined several areas, until the mesh quality check brought back a favourable result. 2/3 Computations then ran and completed thereafter but the third proved more troublesome, this one included actuator disks.

I tried further refining the mesh but this did not help my case. I analysed the monitor and saw an odd occurrence. Visible in the Residuals and 'Fx' mainly, there were large spikes every few iterations: Seen in Capture 1-4.

Captures 1 and 2 are from a computation using a much smaller timestep of about 0.003s and Captures 3 and 4 are using the standard timestep of 0.0124s.

I read through the documentation and saw the section recommending fixes for spikes in the forces, seen in the monitor and that is why I changed my timestep size. I also tried increasing the acceleration ramp from 1s to 1.5s but with no visible difference.

With my last computation, using the standard timestep and a 1.5s ramp, the solver did not crash, however, while the computation would normally be finished overnight, this morning it was only on about 3500 Iterations, compared to the normal 7500 it should have reached. So I believe it is also running slower than usual for some reason.

The 'Fx' had seemingly converged and so I stopped the computation early and inspected the results to find a very odd free surface. Seen in Capture5, the wake is very short and in previous computations of this scenario, prior to adjusting the viscous layers, the wake was better represented and far larger. It also seems as if the free surface is "Stuck" to the fore section of the vessel, rising as high as the deck.

I'm not sure why the free-surface appears this way and I'm not sure if it is related to the spikes seen in the monitor during computation. Has anybody had a similar experience to this, specifically the spikes, and do you have a potential solution?

Thank you.


Capture.JPG

Capture2.JPG

Capture3.JPG

Capture4.JPG

Capture5.jpg
StefanoSic is offline   Reply With Quote

Reply

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
simpleFoam-MRF to rhoSimpleFoam-MRF strange results Krao OpenFOAM Running, Solving & CFD 2 August 20, 2021 15:55
Simultaneous rotation and translation yields strange results with gmsh BPeters Mesh Generation & Pre-Processing 2 November 19, 2018 03:52
[mesh manipulation] Strange results after using refineMesh on radial 2D-Mesh Zarchias OpenFOAM Meshing & Mesh Conversion 1 October 30, 2018 11:57
Strange DNS results LijieNPIC OpenFOAM 14 June 14, 2011 05:30
upwind schema strange results; Solution of Versteeg example differs from OpenFOAM sol idrama OpenFOAM 12 May 10, 2011 06:38


All times are GMT -4. The time now is 09:08.