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

Euler equations with heat conduction!

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 29, 2004, 19:33
Default Euler equations with heat conduction!
  #1
salem
Guest
 
Posts: n/a
Hi every body I am thinking to add heat conduction to Euler equations for solving two dimensional flow. Does this true or the thermal conductivity is related to viscosity which is neglected in Euler equations. if true, any material related to Euler equations with heat conduction.

  Reply With Quote

Old   July 29, 2004, 19:43
Default Re: Euler equations with heat conduction!
  #2
jenn
Guest
 
Posts: n/a
Hi, two things have to be clear:

1) Euler equation is inviscid Navier-stoker equations, which neglects the viscosity diffussion term. While heat conduction equation is another equation. So not sure "..add heat conduction to Euler equations...".

2) thermal conductivity relates to viscosity by Prandtl number. I don't think there is any material which has no viscosity. Of course you can do that numerically.

  Reply With Quote

Old   July 30, 2004, 02:53
Default Re: Euler equations with heat conduction!
  #3
salem
Guest
 
Posts: n/a
thanks jenn for reply
  Reply With Quote

Old   July 30, 2004, 02:58
Default Re: Euler equations with heat conduction!
  #4
salem
Guest
 
Posts: n/a
I use conduction for Euler equation to over come the problem of low density region especially when an airfoil at large angle of attack in that region the internal energy comes negative.
  Reply With Quote

Old   July 30, 2004, 03:58
Default Re: Euler equations with heat conduction!
  #5
Qu Kun
Guest
 
Posts: n/a
Maybe neg energy isn't resulted from absence of heat conduction. Maybe your scheme has not enough dissipation.

Even if heat conduction is added, heat convection still dominates the process of energy transfering. So heat conduction plays little affection.
  Reply With Quote

Old   July 30, 2004, 09:10
Default Re: Euler equations with heat conduction!
  #6
salem
Guest
 
Posts: n/a
Qu Kun thanks for reply do you know some material uses Euler equations with heat conduction. best regards
  Reply With Quote

Old   July 30, 2004, 16:18
Default Re: Euler equations with heat conduction!
  #7
jenn
Guest
 
Posts: n/a
salem:

Let me understand your physical problem first.

1) where is your interested region? In the front area of the airfoil around the stagnation point? I think there is very sharp velocity gradient there or you can say there is boundary layer there. But it DOESN't mean the velocity there is small every where. So you may still put heat convection into the heat equation i.e. u.\grad T as T is the temperature and u is the local velocity. If that region is really thin and there is hugh density drop cross it, there will be shock waves. Then there you have to solve compressible Euler equation combined with heat equation!

2) You mentioned there the internal energy is negative. Internal energy equals the kinetic energy of molecules plus the potential energy among them. Since the molecular energy is alway positive, the negative energy comes from the larger negative potential energy. Or in another word, the distance between two molecules is very big. Is it true in the region you are interested with low viscosity?

  Reply With Quote

Old   July 30, 2004, 18:17
Default Re: Euler equations with heat conduction!
  #8
salem
Guest
 
Posts: n/a
Hi jenn 1) May be there is misunderstanding of my question I am not interesting to heat equation, I mean the heat conduction at the energy equation of the Euler equations, q=-k grad (T). 2) the internal energy numerically may comes negative when the kinetic energy dominates the total energy ,e=E-1/2*rho*(U)^2,when one use Conservative variable as COL(Rho,Rho*u,Rho*v,E)and using the Ghost cell boundary condition, reflection boundary condition wall, I mean when there is expansion wave, the vacuum or near vacuum region occurs ,Pressure~=0.0 any inaccuracies in the conserved quantities can easily lead to the kinetic energy exceeding the total energy, causing computational breakdown in from of internal energy being negative .see paper "W.H Hui and S. Kudriakov, on wall overheating and other computational difficulties of shock capturing methods page 22" you can get it online search by google.

  Reply With Quote

Old   July 30, 2004, 23:53
Default Re: Euler equations with heat conduction!
  #9
Qu Kun
Guest
 
Posts: n/a
Dear salem

I am not familiar with this, although I met the problem of neg energy at the back region of a cylinder, too.

regards
  Reply With Quote

Old   August 2, 2004, 01:26
Default Re: Euler equations with heat conduction!
  #10
Qu Kun
Guest
 
Posts: n/a
Hi, salem

Maybe this paper is usful for you:

Noh W. F. (1987), Errors for calculations os strong shocks using an artificial viscosity and an artificial heat flux, Journal of Computational Physics, 72:78-120
  Reply With Quote

Old   August 2, 2004, 04:16
Default Re: Euler equations with heat conduction!
  #11
salem
Guest
 
Posts: n/a
thanks qu kun
  Reply With Quote

Reply


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
Delta form of Heat, Euler and NS equations RameshK Main CFD Forum 3 May 30, 2012 11:41
Euler equations & expansion shocks technophobe Main CFD Forum 5 April 28, 2009 16:11
Conduction heat not balanced? Nepal CFX 7 May 31, 2005 12:51
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55
Conduction Heat Transfer ? Jim Park Main CFD Forum 1 February 14, 2002 11:53


All times are GMT -4. The time now is 21:25.