[HuifengGong]

Hi,

I want to use CONVERGE to simulate a droplet-laden jet flow, in which fuel droplets are carried out by the air flow through a long tube, forming a two phase spray jet. Now, I have some difficulties in setting the boundary conditions. I intend to use the Eulerian-Lagrangian framework to do this simulation, but I found that the spray modeling in CONVERGE was specially designed for pressurized nozzle spray, and seemed to be not convenient for my simulation. how could I do this simulation in CONVERGE?

I want to set the inflow boundary conditions at the tube outlet, where the velocity distribution of gas phase and the size&velocity distribution of droplets should be designated according to the experimental data, and then the coupling between the gas phase and droplets will be observed in simulation (Does CONVERGE consider the two-way coupling effect?).

Thanks in advance

HuifengGong

[jhuang]

Hi Huifeng,

I think what you may need is similar to VOF-Spray One-Way Coupling (section 16.5 of CONVERGE 2.3 manual). However, for VOF-Spray one-way coupling, VOF simulation writes out a map file as the initial condition for the spray simulation. In your case, you want this map file to be based on experimental results, which is the challenge. Please read section 16.5 of the manual and take a look at the format of vof_map.out. If you think it's possible to write such a file based on your experimental results, we are here to help.

Regarding your second question, the interaction between liquid phase (spray parcel) and gas phase in CONVERGE spray simulation is a two-way coupling. You can find more details in CONVERGE 2.3 manual section 12.4: Drop Drag and Liquid/Gas Coupling.

Hope this helps. Thanks!

[HuifengGong]

Thanks for your advice!

I have looked the manual about this method, but the problem still remains. The VOF result is basically Eulerian, and the vof_map.out file doesn't cover the droplet information (droplet size & velocity). My inlet boundary condition is gas phase (Eulerian-based, continuous) velocity varied with spatial locations and droplet (Lagrangian-based, discrete) velocity&size varied with spatial locations. I'm afraid this method can't fix my problem.

I get another idea from your advice. Since the VOF-Spray One-Way Coupling method is generally some kind of information transmitting, can I transmit any general simulation results to another domain? In my case, the droplet-laden flow goes through a long tube to generate the spray, so, maybe I could do a pipe flow simulation for the tube with spray model in CONVERGE, and gather the gas and droplet information (velocity & droplet size vs location) at the tube outlet. Is there any approach to transmit this information to the further spray simulation?

Huifeng

Originally Posted by jhuang

Hi Huifeng,

I think what you may need is similar to VOF-Spray One-Way Coupling (section 16.5 of CONVERGE 2.3 manual). However, for VOF-Spray one-way coupling, VOF simulation writes out a map file as the initial condition for the spray simulation. In your case, you want this map file to be based on experimental results, which is the challenge. Please read section 16.5 of the manual and take a look at the format of vof_map.out. If you think it's possible to write such a file based on your experimental results, we are here to help.

Regarding your second question, the interaction between liquid phase (spray parcel) and gas phase in CONVERGE spray simulation is a two-way coupling. You can find more details in CONVERGE 2.3 manual section 12.4: Drop Drag and Liquid/Gas Coupling.

Hope this helps. Thanks!

[MFGT]

Originally Posted by HuifengGong

I get another idea from your advice. Since the VOF-Spray One-Way Coupling method is generally some kind of information transmitting, can I transmit any general simulation results to another domain? In my case, the droplet-laden flow goes through a long tube to generate the spray, so, maybe I could do a pipe flow simulation for the tube with spray model in CONVERGE, and gather the gas and droplet information (velocity & droplet size vs location) at the tube outlet. Is there any approach to transmit this information to the further spray simulation?

You could use the map file from that pipe flow simulation with spray modeling, which you the use to initialize the orher simulation domain. Should work

Check chapter 7.1.2 of the Manual.

[HuifengGong]

Originally Posted by MFGT

You could use the map file from that pipe flow simulation with spray modeling, which you the use to initialize the orher simulation domain. Should work

Check chapter 7.1.2 of the Manual.

Thank you very much, MFGT

I have gone through the user manual of this part, but there is still a problem. I think mapping is the kind of method for initialization, while my problem is about defining the boundary condition. What I want to specify are:
1. spatially varied velocity of gas phase;
2. spatially varied velocity of droplet, which could be the same to the gas velocity ;
3. droplet size distribution.

For the first one, I could use the velocity profile to define the velocity distribution, and for the third one, I could use the user defined distribution(injdist.in). The only problem is the second one, to specify the droplet velocity distribution. In the spray model, droplet velocity is generally determined by the injection rate and the nozzle hole diameter, I don't know whether or not there is a way to specify it by the user.