CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT > Fluent Multiphase

How to avoid velocity limiting in homogenous VOF with boundary layers?

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 9, 2023, 12:05
Default How to avoid velocity limiting in homogenous VOF with boundary layers?
  #1
New Member
 
Join Date: Aug 2023
Posts: 15
Rep Power: 2
DrZoidberg is on a distinguished road
Dear CFD community,



I have trouble to get rid of velocity limiting and bad momentum convergence a in homogenous VOF case. The settings were posted in a previous thread if you are interested: Negative Pressure in homogenous VOF with ideal gas and incompressible liquid


Problem: On meshes with boundary layers (y+=1, ~1e-7m first cell height, growth rate 1.2, 12-24 Bl in total) there occurs velocity limiting (limiter set at 300m/s) in order to avoid solver divergence.

Meshes without BL and a cell size of ~0.2mm at the wall do not have this problem. However their y+ is so high (>300), that the boundary layer cannot be modeled by a turbulence model.


Velocity limiting usually occurs at some time steps (approx. 1% of fill time is affected by this) in cells that are filled with the ideal-gas (air) phase and that are located close to the interface (aluminum melt/air) - especailly if an air bubble has formed an moves towards a wall. The high momentum of the neighbour cells filled with liquid (density ratio 1:3000) causes unrealisitc high acceleration of the air in the small boundary layer cells. Additionally, they usually have high aspect ratios.



Maybe I miss something critical here, but do you know how this problem can be solved? I searched the forum and best-practice guidelines but could not find anything on this
Must we decide between "OK convergence but missing physics (no BL resolution)" or "BAD convergence/velcity limiting in some timesteps but at least BL was resolved"?
DrZoidberg is offline   Reply With Quote

Reply

Tags
boundary layer, divergence, mesh, turbulence, vof multiphase

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
3D Windturbine simulation in SU2 k.vimalakanthan SU2 15 October 12, 2023 06:53
Centrifugal fan j0hnny CFX 13 October 1, 2019 14:55
Out File does not show Imbalance in % Mmaragann CFX 5 January 20, 2017 11:20
Wrong flow in ratating domain problem Sanyo CFX 17 August 15, 2015 07:20
Radiation interface hinca CFX 15 January 26, 2014 18:11


All times are GMT -4. The time now is 11:48.