Hello,

I am working on a variable density Flow with turbulence. When I consider compressibility..is it required that I solve the enthalpy equation?.I do know that energy considerations are important. However, If i chose not to consider the importance of the energy in the system...Can i just solve for Rho, U,P, K and Epsilon ( Turbulence) ?? or do i have to necessarily consider the energy equation?

Can somebody direct me to a paper explaining some methodology to solve a compressible turbulent Flow?

Thanks for your time.

CFDtoy

You will have to solve some form of the energy equation if you are dealing with compressible flow. I assume from your comments that you are using a pressure-based solver. If so, the pressure equation has to be modified to account for pressure-density variations. The book by Peric and Ferziger can provide more information.

Hello Ag, You are right. I used PISO algorithm, pressure based solver for the formulation. Should I also use a Energy conservation procedure?

CFDtoy

If you look in the book by Peric and Ferziger you'll find a procedure for building in the energy conservation. In essence the pressure fluctuations are related to both velocity and density variations via momentum, continuity, and a thermodynamic relation between pressure, density, and enthalpy (or temperature). The pressure equation is solved for the pressure fluctuations, and the density and velocity corrections are then computed. You'll also need to include compressibility in your turbulence model.

Just a note. Incompressible flow is an exception, where the energy equation is decoupled from the other transport equations (mass, momentum, etc.), and therefore in this case it may omitted altogether or just solved after other variables were solved. In other cases it is coupled to other transport equations, and therefore should be solved along with the others.

It depends on what is causing the variable density. A fairly wide range of variable density flows at low Mach numbers can be reasonably handled assuming incompressibility and without solving an equation derived from the conservation of energy.

You will have to say more about the physics of the problems you wish to solve before any decision can be taken about the importance of compressibility/incompressibility and the need to solve an energy equation or not.