Help!
 

Hello! I am a student completely new to CFD. I need to give a talk on CFD two-phase flows! and I havent the faintest of ideas. Any simple suggestions where I might find stuff to read. The books I saw never touched the two phase flows. and every else was direct application to two phase flows. I would need some theory about CFD application on 2phase flows. any help would be appreciated.

Gaurav

Re: Help!
 

It is a field for the expert ( a person who spends a lot of time on a very tough problem ). There are two approaches to compute two-phase flow problem, namely, (1), continuum approach, and (2), particle tracking approach. In the first approach, you need to write governing equations for each phase ( say gas and particle phases.) and solve both equations in the similar way. For example, dust particles in air where you have a lot of small dust particles. In the second approach, you first solve the gas phase equations, then do the particle tracking on each individual ones. You can track the location of the particle based on the size , relative velocity to the gas phase, the drag force etc.. The interaction ( force on the gas phase by the particle ) can be included by going through another loop of gas phase calculation through the source term of interaction. Spray of liquid fuel into air could be handled this way. The liquid droplet can also change size or have chemical reactions. In either case, you need to work out the governing equations first. Then find a method to solve these equations.

another question!
 

Thank's John. Now I see why and how the books were just going ahead with two phase solutions. But, in the even that there is a source term for the particle, does the stabiliity and the consistency of the discretizing methods of the governing equations change.

for example, using a lax wendroff scheme (i just know the theory) for the convection (in invisid flow) of two phase particles, will the stability of the scheme change? or will it still be valid for the limit of -1<CFL<1 as it is in single flow case.

Gaurav

Re: another question!
 

i meant in the liimit of -1<CFL<1.

Re: another question!
 

Many many years ago, one of my colleague was working on two phase flow in solid rocket motor using inviscid Euler approach, I remember that stability could be a problem on certain size particles. You maybe able to find the paper on AIAA journal. I am not to be considered as an expert in this field, so, I'd like to hear comments from those who have hands-on experience in two-phase flow calculations.

Re: Help!
 

Every year ASME has published proceedings on Multiphase Flows including CFD/Multiphase Flows. You can also see the book "Multiphase Flows with Droplets and Particles" by Crowe et al., 1998, CRC press.

two phase stability
 

i have the book "Multiphase Flows with Droplets and Particles" by Crowe et al., 1998, CRC press. that book gives the SIMPLE algorithm with the primitive variables and the conservative variables for the compressible flow. but it doesnot mention anything about the stabilities of the numerical formulations at all.

Gaurav