CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > FLOW-3D

multi-block mesh problem

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

LinkBack Thread Tools Search this Thread Display Modes
Old   February 12, 2019, 19:48
Default multi-block mesh problem
New Member
Join Date: Dec 2017
Posts: 15
Rep Power: 3
Farzam is on a distinguished road
Hi all,

I am working on simulating a large pond with several inlets and outlets. Thus, I use multi-block mesh, but a velocity disturbance starts to grow on the inter-block boundaries and spread throughout the domain.

For finding the source of the problem, I decided to make the problem simple, so I simulated a 10m*10m*2m pool with 0.9 water elev. without any inlet or outlet. There is no wind, and no initial vel. It has 2 linked mesh blocks with sizes of 0.5m and 0.25m (Aspect ratio is 1 for both of them). All of the BCs were left as default (symmetry). We expect the velocity remains zero, but after 1000 sec the disturbance starts and after a few seconds it takes over the whole domain.

I already increased Inter-block boundary type coefficient (alphamb), but it didnít help. Smaller mesh size and different turbulence model didnít help either. Other configurations of mesh blocks (nested or overlapping) also cause the same problem

Does anyone have an idea why this simple simulation has this error?
Thank you!
Attached Images
File Type: jpg Mesh blocks.JPG (143.1 KB, 19 views)
File Type: jpg 1000sec.JPG (29.9 KB, 18 views)
File Type: jpg 2000sec.JPG (31.2 KB, 15 views)
Farzam is offline   Reply With Quote

Old   February 13, 2019, 17:50
New Member
Join Date: Dec 2018
Posts: 3
Rep Power: 2
Fast&Furious is on a distinguished road
ِDear user

That is due to interpolation error between blocks. By choosing 1:2 mesh size ratio, and increasing alphamb, and putting the interblock boundary somewhere with less p and v gradient you can only decrease it.
To me this is a big problem of Flow3D that needs to be resolved!!! F3D guys may have a better response for you.
Fast&Furious is offline   Reply With Quote

Old   March 15, 2019, 12:34
Adwaith Gupta
Join Date: Dec 2015
Location: USA
Posts: 75
Blog Entries: 1
Rep Power: 5
thunde47 is on a distinguished road
Try alphamb = 1e-6 and alphamb = 1.0. See if the problem is resolved by setting one of these values.
thunde47 is offline   Reply With Quote


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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
[] Foam-extend-3.1 on RHEL: mesh problem lxwd OpenFOAM Installation 4 March 25, 2017 16:10
[mesh manipulation] Importing Multiple Meshes thomasnwalshiii OpenFOAM Meshing & Mesh Conversion 18 December 19, 2015 18:57
[Gmsh] 2D Mesh Generation Tutorial for GMSH aeroslacker OpenFOAM Meshing & Mesh Conversion 12 January 19, 2012 03:52
fluent add additional zones for the mesh file SSL FLUENT 2 January 26, 2008 11:55
How to control Minximum mesh space? hung FLUENT 7 April 18, 2005 09:38

All times are GMT -4. The time now is 12:53.