CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   Fluent Multiphase (http://www.cfd-online.com/Forums/fluent-multiphase/)
-   -   how to modelling dispersed phase (http://www.cfd-online.com/Forums/fluent-multiphase/118664-how-modelling-dispersed-phase.html)

harkerz June 1, 2013 03:17

how to modelling dispersed phase
 
Hi all, I want to simulate the water droplets in cooling tower using euler multiphase with k epsilon for viscous. The continuous phase is air and the disperse phase is liquid water.

The problem is, I don't know the method to model dispersed phase. What button should I use in ffluent?

oj.bulmer June 4, 2013 11:38

http://www.sharcnet.ca/Software/Flue...tg/node337.htm

harkerz June 5, 2013 12:42

Quote:

Originally Posted by oj.bulmer (Post 431973)

I've just know that dispersed phase was using injections. So, how to couple between continous phase and dispersed phase?

One of injections requiremnt for droplet is two chemical species, but actually water is just one species (h20) right? So, how can i solve it?

oj.bulmer June 6, 2013 06:05

On the discrete phase model dialogue box, enable "Interaction with Continuous Phase". This models the interphase transfer of mass/momentum (and heat if energy equation is enabled) thus discrete phase influences the continuous phase.

I have worked with injection of air etc, without problem. Why do you see it needs two chemical species?

OJ

harkerz June 6, 2013 12:50

Quote:

Originally Posted by oj.bulmer (Post 432392)
On the discrete phase model dialogue box, enable "Interaction with Continuous Phase". This models the interphase transfer of mass/momentum (and heat if energy equation is enabled) thus discrete phase influences the continuous phase.

I have worked with injection of air etc, without problem. Why do you see it needs two chemical species?

OJ

because I rode the tutorial and it mentions that if we activate "droplet", there are two chemical species needed. But, actually I just model water are introduced from spray. So, water just only contains one species right? But the droplet need two chemical species to be active

Behnam Ghadimi June 8, 2013 03:53

Quote:

Originally Posted by oj.bulmer (Post 432392)
On the discrete phase model dialogue box, enable "Interaction with Continuous Phase". This models the interphase transfer of mass/momentum (and heat if energy equation is enabled) thus discrete phase influences the continuous phase.

I have worked with injection of air etc, without problem. Why do you see it needs two chemical species?

OJ

Hi OJ
I have modeled water injection in air, it seems that the temperature and pressure distribution in the fluid domain is correct and all of the equations are converged. but still I have a problem with the inlet and outlet mass flow rate. the following boundary conditions are applied to modeling the water injection in rectangular channel for mass flow rate:
air inlet mass flow rate: 1 kg/s
ware injection mass flow rate at the middle of the channel: 0.5 kg/s
after solving the eqs. with FLUENT Injection modeling, the inlet and outlet mass flow rate are reported as 1 Kg/s, which is equal to the inlet mass flow rate of air.
it seems that the fluent is not used the water droplet injection in solving momentum eq. and only droplets were affect the air temperature and preesure reduction due to the heat transfer and drag force of water droplet, respectively.
Do you have any idea about this problem?

oj.bulmer June 10, 2013 10:14

Quote:

because I rode the tutorial and it mentions that if we activate "droplet", there are two chemical species needed.
You select "droplet" injection only when you are modelling a heat transfer between the phases and there is evaporation/boiling, or when you are modelling a combustion. For a simple case of air in water, you should select particle type as inert.

Quote:

it seems that the fluent is not used the water droplet injection in solving momentum eq. and only droplets were affect the air temperature and preesure reduction due to the heat transfer and drag force of water droplet, respectively.
Can you provide the following values:

Report fluxes >> Mass flux at inlet, outlet and the middle surface of water injection
Report volume integrals >> Options: Sum >> Filed variable: Discrete phase model - DPM mass source

OJ

Behnam Ghadimi June 11, 2013 02:14

Quote:

Originally Posted by oj.bulmer (Post 433126)


Can you provide the following values:

Report fluxes >> Mass flux at inlet, outlet and the middle surface of water injection
Report volume integrals >> Options: Sum >> Filed variable: Discrete phase model - DPM mass source

OJ

Dear Oj
thanks for your reply
The values of your interest are reported in follows:

Mass Flow Rate (kg/s)
-------------------------------- --------------------
air-side-inlet 1
air-side-outlet -1
---------------- --------------------
Net 1.110223e-16

Mass Flow Rate (kg/s)
-------------------------------- --------------------
middle_line 0.9985739

Sum
DPM Mass Source (kg/s)
-------------------------------- --------------------
fluid 0

It is very strange, DPM mass source is zero!!!
Are you have any idea?
Do you think I have any mistake in my modeling procedure?
the water was injected into air and I can see the temperature difference due to the injection.
Thanks a lot.

oj.bulmer June 11, 2013 10:55

Yes, this is strange. Can you also report the following:

Report ->Discrete Phase->Summary, Select all the injections and click on Summary

OJ

Behnam Ghadimi June 11, 2013 15:09

Quote:

Originally Posted by oj.bulmer (Post 433406)
Yes, this is strange. Can you also report the following:

Report ->Discrete Phase->Summary, Select all the injections and click on Summary

OJ

Dear OJ
Thanks for your reply
Summary menu is inactive in my case, I can not report this value.

harkerz June 13, 2013 03:40

Quote:

Originally Posted by oj.bulmer (Post 433126)
You select "droplet" injection only when you are modelling a heat transfer between the phases and there is evaporation/boiling, or when you are modelling a combustion. For a simple case of air in water, you should select particle type as inert.



Can you provide the following values:

Report fluxes >> Mass flux at inlet, outlet and the middle surface of water injection
Report volume integrals >> Options: Sum >> Filed variable: Discrete phase model - DPM mass source

OJ

Actually Im modelling a heat and transfer between the phases, because in my cooling tower, the hot water introduced from top of the tower and the cold air is cooling the water.

So, how I can solve this?


All times are GMT -4. The time now is 07:38.