Learning Forum

[snr1]

I am modelling the absorption process by using the Eulerian multiphase model with species transport model along wth energy equation. For mass transfer, i.e. interaction between the phases, species mass transfer model has chosen. Timestep value = 1e-6 has chosen then initialization was done and after that simulation was run and it immediately results in the following error:

 

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: solution-species-0

Divergence detected in AMG solver: apour-species-0

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: solution-species-0

Divergence detected in AMG solver: apour-species-0

Divergence detected in AMG solver: vof-1

Divergence detected in AMG solver: pressure correction

Divergence detected in AMG solver: solution-species-0

Divergence detected in AMG solver: apour-species-0

Divergence detected in AMG solver: vof-1

Error at host: floating point exception

 

Error at Node 0: floating point exception

 

Error at Node 1: floating point exception

 

Error at Node 2: floating point exception

 

Error at Node 3: floating point exception

 

Error: floating point exception

Error Object: #f

 

Calculation complete.

 

 

How to solve this error.

 

Thanking you

 

[snr1]

 

[snr1]

[snr1]

[Amine Ben Hadj Ali]

Can you please add more details about the case: mesh, quality, models, boundary conditions and release version.

[snr1]

The geometry is as follows:

There is a pipe and at the bottom of pipe nozzle is there. Through nozzle gaseous mixture will flow and through the annulus solution mixture will flow. The meshed domain is as shown in below:

 

Quality:

 

models:

1. Multiphase-Eulerian model

2. Energy

3. SST k-w turbulence model

4. Species transport model with species mass transfer in phase interactions.

 

Boundary conditins:

1. Nozzle inlet: Mass flow inlet

2. Solution inlet (Annulus) : Mass flow inlet

3. Nozzle wall : Adiabatic

4. Pipe wall : Heat flux (negative)

5 Outlet : Pressure outlet

 

Fluent version : 18.1

[Amine Ben Hadj Ali]

Try to avoid huge cell volume change at the end of the small pipe nozzle. Please use one of the last releases and try again. We ameliorated several things which you are using now.

[snr1]

How i can avoid the huge cell volume change at the end of small pipe sir?

Can i know which things were amelorated in the latest version? and from which version onwards these are implemented?

[Amine Ben Hadj Ali]

Use the latest possible versions. Mass transfer and stability have been enhanced.

For volume cell change, mark cells with cell volume change larger than 2..5: you need to get ride of them.

[snr1]

Thank you sir for you reply. But, i dont know how to mark the cells with cell volume change larger than 2.5? can you please elobrate it how to do this.

 And i am using latest version of 18.1 only sir.

Thanks

[Amine Ben Hadj Ali]

Using Adaption Registers.

Latest version is 2019R2. After 18.1, we have had 18.2, 19.0, 19.2, 19.2 and 2019R2.

[snr1]

Dear sir, after adaption of grid also, still the same error is coming.

How reslove this issue

[Amine Ben Hadj Ali]

I have not said do adaption: I said check the region where the cell volume change is large and remesh accordingly. I also said update to the latest possible release. If then still having issues we can discuss further steps.

 

What you can do is at first to disable mass transfer and check if it is running through.

[snr1]

Currently, my institute doesnt have the recent release fluent version license.

I have done the remesh where the volume has exceeded the 2.5 by using adapt volume.

With out mass transfer the case is working fine.

[Amine Ben Hadj Ali]

And the mass transfer is via? Please screenshots of all interaction panels.

[snr1]

[Amine Ben Hadj Ali]

Henry's law us for modelling adsorption or dissolution of gas in a ideal solution. Try changing from to phase and use latest release.

[snr1]

1. Dear sir, according to the theory guide henry law is used for the non-ideal solutions. Here, my application is absorption of gas bubbles in the liquid solution which non-ideal.

2. I didn't get what do you mean changing from to phase?

3. Regarding the latest release, my institute currently having 18.1 only.

4. Will it be possible to model the gas absorption in a liquid solution by using Fluent? If so, which version will be helpful and which models?

[Amine Ben Hadj Ali]

1/Check the graph of Henry and Raoult and you will see that is not good for non-ideal solution only when the component mass fraction is small: dilute conditions

2/You change the phase order in the species mass transfer panel

3/okay. not good

4/Yes either with Henry's law or via UDF

[snr1]

 1. Means in dilute conditions, for non-ideal solutions, Henry's law won't applicable?

2. In my case, the vapour phase is having a higher mass fraction (0.99), and a solution is having a mass fraction of 0.2 so that the mass will transfer from vapour to solution-phase by species mass transfer.

3. With henry's law, we have to specify the reference henry constat and temperature dependence, which I don't for my present working pair?. how to calculate that?

[Amine Ben Hadj Ali]

1/In dilute conditions Henry law is applicable. 

2/You need to apply the mass transfer always from liquid to gas: you need just to inverse the order.

3/That your input: make a literature survey.

[snr1]

Dear sir, but in my case, the condensation process is happening. Still, I have to give my transfer from phase as a liquid? But in the actual condensation process, from phase is vapour, so I have given like that. Kindly clarify the doubt.

[Amine Ben Hadj Ali]

It does not matter if dissolution or adsoprtion: The mass transfer has to be set so that on left side you liquid and the right side gas.

[snr1]

Dear sir, in species mass transfer modelling, whether we have to specify the same species or different species in from and to species?. i.e. whether we have to give from species as water liquid in one phase and to species also as water liquid in another phase or water liquid in one phase and to species as water vapour in another phase?

[Amine Ben Hadj Ali]

In the phase interaction panel under Mass. 

 

[snr1]

Thats fine sir. But, what my doubt is that,  whether we have to specify the same species or different species in from and to species?. i.e. whether we have to give from species as water liquid in one phase and to species also as water liquid in another phase or water liquid in one phase and to species as water vapour in another phase?

[Rob]

Depends whether you're transferring between two liquids or liquid to gas? 

[snr1]

I am transferring species from gaseous phase to liquid phase, i.e. condensation. My doubt is that, whether I need to specify the same species for species mass transfer or not?