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

Steady state

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

LinkBack Thread Tools Display Modes
Old   June 27, 2006, 01:13
Default Re: Steady state
Posts: n/a
Thanks Praveen!!
  Reply With Quote

Old   June 27, 2006, 06:43
Default Re: Steady state
Posts: n/a
Ruben OP:

I'm writting a code for solving the Euler equations of compressible flow.

I'm interested in state state solutions and I have problems with the oscillations. Even in the subsonic case I have spurious oscillations and the convergence is too slow. I think that I need a time integration scheme with damping. What scheme can I use?


diaw comments:

After all has been said & argued on this thread, & after spending a while reviewing both Euler & Potential derivations & equations forms, I must say that I fail to see a useful valid connection between the two.

Potential flow:

Irrotational flow => transform via u=d(phi)/dx ; v=d(phi)/dy

=> d2(phi)/dx2 + d2(phi)/dy2 =0

Euler flow (weak form):

d()/dt + u.d()/dx + v.d()/dy = f(x,y,t)

The two are completely different animals:

1. The Laplace equation is going to either decay/grow in time, if a d(phi)/dt is bolted on & dependent on the sign used & possibly some forcing function. If in steady form, then we have a nice smooth shape.

2. Euler eqn is a convection flow which is inherently unstable & wants to produce instability, waves & the like. Not too smooth at all...

If you really begin to look deeply into the physics of what these forms actually represent, they are very different.

I have no doubt that the OP sees waves - & so he should with a good algorithm. It is a poor algorithm that adds unwanted numeric viscosity.

  Reply With Quote

Old   June 27, 2006, 17:17
Default Re: Steady state
Posts: n/a
Thnaks for your comments diaw.
  Reply With Quote

Old   May 7, 2011, 03:32
New Member
m p
Join Date: Nov 2010
Posts: 15
Rep Power: 9
moein_joon27 is on a distinguished road
what are the correct boundary conditions for this problem? we need 4 in 2D .among them one is extrapolation which I use riemann invariant extrapolation,but what are the others when we have the inlet mach number?
moein_joon27 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
plz help,urgent, vof model steady state Garima Chaudhary FLUENT 3 November 13, 2017 03:35
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
Constant velocity of the material Sas CFX 15 July 13, 2010 08:56
mass flow in is not equal to mass flow out saii CFX 2 September 18, 2009 08:07
steady state, laminar vof_model Garima Chaudhary FLUENT 0 May 24, 2007 03:11

All times are GMT -4. The time now is 20:44.