CFD Online Logo CFD Online URL
Home > Forums > General Forums > Main CFD Forum

Injection of gas into tube with small holes - Supersonic flow

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

LinkBack Thread Tools Search this Thread Display Modes
Old   December 5, 2018, 06:49
Default Injection of gas into tube with small holes - Supersonic flow
New Member
Join Date: Dec 2018
Posts: 1
Rep Power: 0
mrsl is on a distinguished road
Hey guys,

as this is my first post here, I would like to introduce myself: I am a research engineer in the area of combustion engines. Right now I am dealing with injecting - lets call it - gas A into the port of an engine.

For this I use a tube (15 mm inner diameter) with smal holes (4 mm inner diameter) in it. Gas is injected into the "main tube" and then exits through the small holes. The problem is that the flow accelerates to supersonic speeds as it passes the small holes. I think this causes the simulation to diverge. When I use another gas (gas B with ~ 8 times the density of gas A) and use the same mass flow BC (--> lower velocities) I have no problems with convergence. Gas B and 8 times the gas A mass flow causes also divergence. So the high velocities seem to cause the problem.
My mesh cell size is 0.25 mm in the area of the small holes and my timestep is approx. 0.05 ms.

I am sorry for the more or less little information but as there are industry partners involved I am not able to post much information. I would like to but I can't.

Basically my question is: Why the flow becomes supersonic if this is no laval nozzle and can this cause the divergence problem? Right now I am using 0.005 ms as a timestep to see if this helps.

Best regards and thanks in advance
mrsl 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 Off
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Issues on the simulation of high-speed compressible flow within turbomachinery dowlee OpenFOAM Running, Solving & CFD 11 August 6, 2021 06:40
[How to obtain supersonic flow inside a supersonic wind tunnel ?] yx213 Siemens 1 September 17, 2014 13:52
back pressure at exit for supersonic flow BigFrank FLUENT 6 April 24, 2014 15:13
Non-steady flow simplified for use in Vissim steamerandy Main CFD Forum 0 October 31, 2011 21:08
pipe flow with normal injection through holes Fred Song CFX 2 December 21, 2006 10:42

All times are GMT -4. The time now is 02:44.