Dissolved oxygen

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pinardagistan posted this 07 April 2019

Hello,

The model that I'm working with is a lake and I'm developing an aeration system for it. I have initial dissolved oxygen data with respect to depth within the lake. How do I add dissolved oxygen feature to the model and how should I get the results as dissolved oxygen amount at the end of the simulation?

(The model is multiphase: water and air(not pure oxygen) coming from the aerator.)

Regards.

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abenhadj posted this 08 April 2019

The liquid phase to be defined as a mixture of water and dissolved oxygen.

Best regards, Amine

abenhadj posted this 04 December 2019

Better create a new thread and add more details.

Best regards, Amine

mikel posted this 07 January 2020

Hi again, I will put more details:

I know that the change of the temperature change the disolved oxygen that is in wáter and this creates bubbles in water so I want to simulate this. I think that is posible to use the eulerian multiphase model but i am not sure. Do you have any idea?

 

abenhadj posted this 07 January 2020

Yes that can he done with Eulerian and mixture model (slip on). Other possible way using DPM with custom laws.

Best regards, Amine

mikel posted this 09 January 2020

Hi

Do you mean that I have to use the mixture model inside of multiphase models?

Thanks

mikel posted this 09 January 2020

If I use the eulerian model, the result dont change changing the temperatura. The eulerian model dont take into account the change of the temperature.

abenhadj posted this 09 January 2020

It should take.

Best regards, Amine

mikel posted this 10 January 2020

Thanks for your advice but in the case of the multiphase models, the volumen fraction equation doesnt take into account the temperatura so I cant see any difference in the oxygen volumen fraction distribution when I change the temperature. How can I resolve it?

abenhadj posted this 10 January 2020

You need to solve the energy equation if you want to see temperature field and temperature differences. 

Again: You want to account for temperature change which will affect the solubility of dissolved oxygen in water. At higher temperature you will expect the creation of more bubbles etc.. in other words the Henry's law. To do that either EE model or Mixture with Slip or customizing DPM model.

 

 

Best regards, Amine

mikel posted this 10 January 2020

Thanks, I know that I have to modelate henry's law. For that also I have to actívate species transport and define my mixture that is water and oxygen. Ones I have this which are my primary and secondary phases in the multiphase model? Also how can I apply the species mass transfer? from which species to wich species?

Thanks

abenhadj posted this 10 January 2020

The primary phase is the continuous one. Mass transfer always from liquid side to the gaseous side (inbuilt).

Best regards, Amine

mikel posted this 10 January 2020

Hi again, the equation of the energy doesnt work well--> "temperatura limited to…" and the temperatura in the results is not correct. Why happens this?

Thanks

abenhadj posted this 10 January 2020

Large exchange source terms and/or wrong setup.

Best regards, Amine

mikel posted this 10 January 2020

Hi again, I define an Eulerian multiphase model and I actívate species transport. I define two mixtures, one is water (primary phase) and the other one oxygen (secondary phase). Then I apply species mass transfer from wáter to oxygen. Could be this correct?

Thanks

abenhadj posted this 10 January 2020

No. You need a multicomponent primary phase.

Best regards, Amine

mikel posted this 10 January 2020

Primary phase (water+oxygen) and secondary phase (only oxygen)? Then species mass transfer from water to oxygen?

abenhadj posted this 11 January 2020

Sounds okay.

Best regards, Amine

mikel posted this 11 January 2020

Hi again, in the initialization I have to put the mass fraction of O2 at 25Cº and with that is enough? or I have to put also the volumen fraction of my secondary phase? I want to visualize only the change of the disolved oxygen in wáter...

mesakca posted this 2 weeks ago

Hi Amine

In my problem, (gas dissolution in water) the experiments were held on constant temperature (21 C)

Do i need to turn on energy equation to include effect of this?

Thank you.

 

abenhadj posted this 2 weeks ago

If you require a built-in van't hoff correlation it will require just to set the temperature on 21 C. Enable Energy Equation, set the temperature to 21 C (Initialization and all boundaries) and do not solve the energy equation. But bear in mind that doing this you will aslo ignore the secondary source terms due to phase change (might be okay as they are very very small and might be ignored here).

Best regards, Amine

mesakca posted this 2 weeks ago

I didn't understand what you mean by do not solve the energy equation?

I will enable energy equation and set the temperature to 21 C at initilization and boundaries. After that should i turn it (energy equation) off again?

 

abenhadj posted this 2 weeks ago

You can disable equations in Fluent even if the model is turned on. Look in Solution Controls.

Best regards, Amine

mesakca posted this 2 weeks ago

OK. Thank you very much sir.

abenhadj posted this 2 weeks ago

Next time open new thread You are welcome.

Best regards, Amine

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