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Species Mass Transfer - results keep diverging

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Old   June 29, 2021, 00:10
Default Species Mass Transfer - results keep diverging
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Stanlee
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Hi everyone,

I am trying to simulate the natural evaporation of a thin water film. Basically, there is dry air passing through above the water liquid film, and the water liquid is expected to evaporate into the dry air. Basically, I wanna reproduce the simulation in this link (https://www.youtube.com/watch?v=uuIq...annel=AkiraIto).

I used the Eulerian Multi-Fluid VOF model, with the first phase being a mixture of air and water vapour, the second phase is also a mixture but only contains water liquid. I used the species mass transfer and kept the saturation pressure as default. The pics show the settings and boundary conditions. The result diverged almost immediately after the simulation began. The time step is 0.00005 s, so the courant number is no way greater than 250.

If I did not patch the water liquid in the domain, it worked without any errors.

Please help me!! Thank you!

The errors show below:

Error at Node 2: Global Courant

Error at Node 4: GlEE

Error at Node 5: Global Courant number is greater thr number is greater rothan 250.0an 250.00 The

vel0 The

velocitocityyr field atrror a Nod f is probably diverging. Please cheeield is pt 1 Node ck the solution

0: Global Couraand reduce the time-stent number is greater p if necessthan 250.: Global Cary.

00 ouobal Courarnt nant number is greumber isater t ghan 250.00 The r

velocity fe ield isThe

velocit probablyy fiel divergid is probng. Pleaseably d check tiverging. Plehe solution

and redase check the solution

and reduce the time-step if necessary.

uce the time-step if necessary.

ater than 250.00 The

velocity field is probably diverging. Please check the solution

and reduce the time-step if necessary.

robably diverging. Please check the solution

and reduce the time-step if necessary.

Error at Node 3: Global Courant number is greater than 250.00 The

velocity field is probably diverging. Please check the solution

and reduce the time-step if necessary.







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Old   June 29, 2021, 07:40
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Lorenzo Galieti
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Did you try to reduce the timestep a lot? Look that a courant of 250is freaking high for complicated physics like the one you are simulating
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Old   June 29, 2021, 16:16
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Stanlee
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Hi Logal,
The current time step is 0.0005, mesh size is 0.002, velocity is 1 m/s, so the courant number should 0.025..it is low enough i think.
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Old   June 30, 2021, 17:09
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Lorenzo Galieti
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Sorry man but I read 250 in the log you are posting, clearly something you miscalculated?
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