
[Sponsors] 
December 30, 1999, 17:38 
What is Boussinesq equation?

#1 
Guest
Posts: n/a

Hi, there,
Is there anybody who can tell me what is Boussinesq equation? Is it the energy equation + NavierStokes equations? Could anybody can tell me where can find some online reference about heat transfer? Thanks a lot. Have good holiday. bao 

January 3, 2000, 03:32 
Re: What is Boussinesq equation?

#2 
Guest
Posts: n/a

The Boussinesq assumption is that the turbulent stresses are directly proportional to the velocity gradient, ie turbulence can be modeleled as an eddy viscosity.


January 3, 2000, 10:44 
Re: What is Boussinesq equation?

#3 
Guest
Posts: n/a

Jonas, I'm sorry but he was talking about the Boussinesq equations, not the Boussinesq linear stress tensor approximation. The BE may be understood as a simplified version of the full set of NavierStokes equations, i.e. continuity, momentum and heat equations. The simplification is attributed to the followings: i) effect of thermal expansion is limited to a linear buoyancy force; ii) usually, viscous dissipation of energy is neglected, and iii) all fluid properties (density, viscosity and thermal diffusivity) are assumed to be constant. In another words, you've got to solve a set of 2*d+1 equations (here d stands for the dimension of the problem). The set is strongly coupled (coupling is stronger than for the NSE for isothermal flows). Good starting would be reading of classical heat transfer books in your local library, not looking for crap on the internet. It's never late to do the latter.


January 3, 2000, 10:55 
Re: What is Boussinesq equation?

#4 
Guest
Posts: n/a

Ah, that's news to me, I'm sorry if I mislead anyone. I never even heard about the Boussinesq Equations. It is not a very common term in CFD. Thanks for correcting me.


January 3, 2000, 22:53 
Re: What is Boussinesq equation?

#5 
Guest
Posts: n/a

Hello Jonas:
I understand the confusion. Boussinesq approximation you were referring to is found in the Turbulence Modeling literature. Boussinesq equation Yangang Bao was reffering to can be found in classical heat transfer text books. I think it refers to the modifications made to momentum equations while dealing with free convection problems. Unfortunately, both carry the same name. Probably, one needs to be bit specific when talking about the above. Thanks, Thomas 

January 4, 2000, 12:27 
Re: What is Boussinesq equation?

#6 
Guest
Posts: n/a

Thomas, yeah, it is quite common that we encounter such confusions. For example, even talking about the NavierStokes equations, do people imply only momentum equations, or the full set of equations that govern the phenomena? The problem is with the terminology, though... As for your post, I'd like just to add that the Boussinesq equations are valid not only for free convections problems, but also for mixed ones (free+forced). Once stratification is present and conditions (i)(iii) in my previous post are met, the full set of NSE reduces to the BE's. Otherwise, the equations are more complex. Regards


January 5, 2000, 04:19 
Re: What is Boussinesq equation?

#7 
Guest
Posts: n/a

So.. I would assume that the Boussinesq Equations is the incompressible set of NavierStokes equations adding the Boussinesq approximation for the density variation, correct or not? The confusing about Boussinesq isn't total however, since the denotation is Boussinesq hypothesis, or assumption regarding the eddy diffusivity linear relation with velocity gradients. However I maybe adding confusion because this is another Jonas posting this...


January 21, 2000, 22:09 
Re: What is Boussinesq equation?

#8 
Guest
Posts: n/a

There is one equation about the particle motion in multiphase flow called: "BassetBoussinesqOseen equation". I am not sure if it is what you mentioned. Just for referring.


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
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 
Viscosity and the Energy Equation  Rich  Main CFD Forum  0  December 16, 2009 15:01 
mass flow in is not equal to mass flow out  saii  CFX  2  September 18, 2009 08:07 
What is the Boussinesq Term in Momentum Equation  CFDtoy  Main CFD Forum  0  August 11, 2008 09:56 