CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > ANSYS > FLUENT

Air filter holder, questions about high turbulence viscosity and convergence

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

LinkBack Thread Tools Search this Thread Display Modes
Old   January 24, 2019, 15:38
Default Air filter holder, questions about high turbulence viscosity and convergence
New Member
Join Date: Jun 2013
Posts: 1
Rep Power: 0
clmr90 is on a distinguished road
Good day for everyone,

My case is the flow simulation of a filter holder (the carcass) where I need to calculate the pressure loss at the end. Sadly I had several problems using different configurations. It started as a way of helping a professor from my uni but now I am taking it as a personal challenge.
First I used a pressure inlet for the entrance of the flow and a mass outflow for the exit (0.1104kg/s as the engine needed). I am entering 98800 pa as operating pressure and locating the point of reference near the entrance (there are some losses from the tubes that conduct to the air to the inlet, obtained experimentally from the people that I am helping). Also, I had turbulence intensity as 5% and 0.066 for the hydraulic diameter. I started using the k-e realizable with enhanced wall functions but I could not get any sign of convergence at all after 400 iterations and the warning of high turbulence viscosity could not dissapear. Interestingly enough my max y+ was about 2421 which I though it was strange so I tried using the other turbulence models such as standard k-e with the same mesh (about 2.4 million cells) and k-omega standard and sst with a more refined one (3.1 million cells). Again, I didn’t get convergence (specially the continuity equation, like a flat salt lake) but I didn´t get any high turbulence viscosity warning or high y+ (about 80 for the std k-e and 50 for the k-omega’s ). My first question is why would that happen with k-e realizable and not with the others.

After that I tried changing my boundary conditions as pressure inlet and pressure outlet with a target mass flow and after 4000 thousand iterations I got a very small convergence with the standard k-e and the k-omega. Finally I changed to mass flow inlet and outflow and with that I got a better convergence but just around 3*10-2 with the continuity equation.
So I am still thinking what to do improve or change. I was thinking of using the RSM since there was a lot of rotation and maybe it can qualify as a swirl flow. Also, since my total pressure never converged to a stable value and always changed (sometimes very rapidly) I was thinking of a transient simulation.

So I hope I can get your feedback in what to do next. You can see the geometry and the flow from the last simulation in the pictures attached.

Thank you
Attached Images
File Type: jpg geometry.JPG (42.1 KB, 3 views)
File Type: jpg streamlines_k-e-4000 iterations.JPG (77.4 KB, 3 views)
clmr90 is offline   Reply With Quote


filter, k epsilon, k omega sst, turbulence, viscosity ratio

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
Turbulence Viscosity Ratio issue in EXtended domain with Pressure Far Field BCs Muneeb FLUENT 0 December 6, 2018 15:48
Wrong flow in ratating domain problem Sanyo CFX 17 August 15, 2015 06:20
HIgh viscosity - convergence issues manxu FLUENT 0 February 12, 2014 08:57
air bubble is disappear increasing time using vof xujjun CFX 9 June 9, 2009 07:59
convergence problem with high viscosity Jan CFX 0 February 29, 2008 04:01

All times are GMT -4. The time now is 00:42.