CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Simulation time for steady state solution using transient solver

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

Like Tree1Likes
  • 1 Post By FMDenaro

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 26, 2019, 05:03
Default Simulation time for steady state solution using transient solver
  #1
New Member
 
Sebastian Pelletier
Join Date: May 2019
Posts: 12
Rep Power: 6
spelletier is on a distinguished road
This may be a slightly silly question and I`m probably misunderstanding how transient simulations run, but when I am trying to determine what an acceptable real run time for a transient simulation that is meant to find a final steady state solution. Can I base my assumption on the travel time of the fluid through the domain?

For example if the fluid is traveling at 10m/s and the domain is 1m in length is it safe to assume that the approximate length of a single real time period would be .1s? or is the total simulation time not analogous in that way to fluid velocity?

If my values of interest (Heat transfer coefficient) appears to have reached steady state would using this estimation be another appropriate check?
spelletier is offline   Reply With Quote

Old   June 26, 2019, 05:08
Default
  #2
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,738
Rep Power: 71
FMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura about
Quote:
Originally Posted by spelletier View Post
This may be a slightly silly question and I`m probably misunderstanding how transient simulations run, but when I am trying to determine what an acceptable real run time for a transient simulation that is meant to find a final steady state solution. Can I base my assumption on the travel time of the fluid through the domain?

For example if the fluid is traveling at 10m/s and the domain is 1m in length is it safe to assume that the approximate length of a single real time period would be .1s? or is the total simulation time not analogous in that way to fluid velocity?

If my values of interest (Heat transfer coefficient) appears to have reached steady state would using this estimation be another appropriate check?



No, you get only an estimation for the convective time in which a fluid particle travels in to the domain.
For laminar steady flow, one can assume the non-dimensional time for a steady state to be proportional to the Re number. But in case of a URANS formulation used to get towards the steady RANS solution this is more complex as the physical viscosity is locally changed by the turbulence model.
The proper check for the steady state is to use a specific norm on the time derivatives of the variable. Theoretically they should vanish, in practice you can set a proper threshold.
spelletier likes this.
FMDenaro is offline   Reply With Quote

Reply

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
courant number increases to rather large values 6863523 OpenFOAM Running, Solving & CFD 22 July 6, 2023 00:48
[solidMechanics] Support thread for "Solid Mechanics Solvers added to OpenFOAM Extend" bigphil OpenFOAM CC Toolkits for Fluid-Structure Interaction 686 December 22, 2022 10:10
pressure in incompressible solvers e.g. simpleFoam chrizzl OpenFOAM Running, Solving & CFD 13 March 28, 2017 06:49
How to write k and epsilon before the abnormal end xiuying OpenFOAM Running, Solving & CFD 8 August 27, 2013 16:33
time step and iterations in steady state problem using transient solver jing113cn FLUENT 2 January 15, 2010 04:18


All times are GMT -4. The time now is 11:18.