Hi guys

I am very new in multiphase flow modeling and I have to make a choice between CFX-5 and FLuent. I want to have a clue of the performance of CFX-5 versus FLuent in terms of multiphse flow modeling. Your information is appreciated.

Hi Paul,

Last year I had to perform numerical simulation sof two phase gas-liquid flows. First, my colleague and I tried to solve it with CFX, after three months, we could not get anywhere with it and I decided to switch to fluent. After one month, I had a first 2D model ready, the 3D model came about two months later.

I think that both CFX and Fluent are good software. But I think that Fluent have the following advantages:

1) Geometries are easier to built with gambit than CFX geometry package;

2) User defined routines are much easier to set up with Fluent.

3) At that time, CFX 5.5 could not handle 2D geometries. 2D problems could only solved in a 3D domain. (But this could have changed by now.)

Nevertheless, my colleague uses CFX to solve problems that involve combustion and transport of chemical species and is very happy with the solver.

BTW, What kind of multiphase flow do you want to solve?

Regards.

Hi Sed,

Appreciate your information. In fact, I am trying to solve gas-liquid pipe flow, such as stratified, annular, and slug flow. More importantly, I am going to look at the interactions of entrained droplets with the gas either liquid phase. Now I am doubting that annular flow can be simulated by CFX or FLuent without model modifications, not to mention droplets. So, it's good to know that it is easier to set up UDF than user fortran.

Regards

I am in the model development group of a company that makes fuel for boiling water reactors. The pressures are at about 69 bar and the flow is annular. What we have found is that cfd codes will not handle annular flow. The major problem is that one of the major things about annular flow is that the deposition and pick up of droplets are controlled somewhat by the wave height. However, the wave height is about the magnitude of the numerical roundoff. If the code sees the wave at all, it thinks it is numerical diffusion and rounds it off. Therefore, empirical methods are necessary to simulate this regime. Regards, Tom

Tom,

I guess you are right. In order to catch the wave, it might be necessary to have very fine grids near the wall region. But for annular flow, even horizontal, it is believed that the unbalanced Reyolds stress caused secondary flow can carry liquid against all the way to the top of the pipe. The key here is that we have to use Reynolds stress model instead of k-e model. I guess the Reynolds stress model is not widely accepted for multiphase flow. But for vertical annular flow, the lateral dispersive forces are crutial to firm the liquid film around the pipe althouth the effects of these forces dispear for fully developed annular flow. My major concern is that all these physics are not reflected in the current two-fluid model. Although we may get some converged results using VOF, lot of details are missed out.

Regards

Hi Paul,

for that kind of similation you are interested in, Fluent offers more than one multiphase models : drift-flux (slip model), VOF and complete euler-euler are available.

Did you give a look at FLOW3D? This code is specialized in multiphase flows. Good Luck.

Have a look at FOAM

http://www.nabla.co.uk

It is also free for academic use.

[meangreen]

MFIX is also free. Its not as user friendly, but if you know the physics and the general idea of CFD you will be fine.

[Kanarya]

hi,

I would like to simulate circulating fertilized bed in OpenFoam...I am new in it.Could somebody tell me which solvers are available for this.

thanks in advance

Recep