CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Steady or transient?

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

LinkBack Thread Tools Display Modes
Old   December 13, 2011, 10:02
Default Steady or transient?
New Member
Join Date: Dec 2009
Location: Italy
Posts: 23
Rep Power: 9
SerSe is on a distinguished road
Dear all,

I am analysing the flowfield of an air nozzle inserted into a hot gas pipe. Temperature of the gas is about 1000K, temperature of air is about 400K. Fluids move by pressure differences. Both materials are modelled as AIR and GAS with ideal gas behaviour and same properties (viscosity, specific heat, etc.) changing with temperature. Given the large differences in pressure, velocity, temperature, etc., I have two materials and two domains to initialize the solution with air in the nozzle and gas in the pipe. It is a 2d axisym steady problem with k-e turbulent model ON, solved by the density-based solver.
When I calculate the solution (I have tried with mass flow inlets as well as pressure inlets), it tends to converge but I get strange results (such as step changes in temperature at the nozzle exit, low Mach number in the nozzle though it should be 1 at the throat from manual calculations, etc.).
I am wondering if changing the model to transient might help!

Moreover, as I am interested in air-gas mixing, I wonder if I have to use the species model! From the "mixing elbow" tutorial, it seems that I could study mixing phenomena without species model ON.

Thank you very much for your help!


SerSe is offline   Reply With Quote


Thread Tools
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
Laminar gas flow under slight suction - transient works but not steady audrey CFX 1 September 8, 2011 19:43
Steady solution from Transient simulations wawa FLUENT 2 November 9, 2010 18:44
Mass Diffusion: Transient and Steady State BC rval CFX 3 November 19, 2008 01:52
Transient vs Steady State Adam CFX 1 April 12, 2007 11:34
Difference between steady and transient problems Jianping Zhang Main CFD Forum 9 April 14, 2003 06:17

All times are GMT -4. The time now is 21:55.