Discussion Forum

Hi Alexey,

You might want to read the model library model on phase change, this includes some graphs which show what is meant here.

1. What is the parameter "Ratio of specific heats"
en.wikipedia.org/wiki/Heat_capacity_ratio
2. Transition interval between Phase1 and Phase 2 - how much should be this parameter?
Depends on mesh size and overall temperature differences in the model. I would advise to test several settings, and compare the results. Say for water -> ice start with a value of around 1K, and for steel melting 20K or so.
3. How to set the variable conditions depending on the time?
You can create a function, say interpolation, and use that function in your physics. The input should then be "t". Note that this is also done in the model library example, so that should help you out as well.

Good luck modelling!

Best regards,
Frank

Hello, Frank!

Very much for your answer!

Could you tell how much this value (ratio of specific heats) for water? I take is 1 - this is correct?
Thanks, I will be trying various value mesh. (my problem temperatures range from -5 to +60 [degC]).
It did you mean? (see pict.) But this dont work.

Best regards,
Alexey

Dear Alexander,

For ice to water you can use 1 indeed.

Regarding your screenshot, you need to specify the functions under definitions before you can use them. As you did not include your whole model, I have no way of seeing what you did there.

Please add the model so I can see what is happening there.

best regards,
Frank

Dear Frank,

This is my model, please, see it. yadi.sk/d/nRRxBU_-a4BSH

Best regard,
Andy

Dear Andy,

I notice that you only got a warning (yellow) for the functions because of the units that were inconsistent. You can usually ignore that, but I attached your file where I fixed it for you.

Under the functions, you can fill in the units of the arguments and the function itself.
Note that you can also specify that the output is in degC, and then you can skip the +273.15.

Furthermore I slightly adjusted your mesh to better follow the changes in the time.
And I set the interpolation of the functions to "piecewise cubuc", this smoothens out the function so the derivative is continuous as well.

Good luck with your model.

Best regards,
Frank

Dear Frank,

Thank you so much! You helped me a lot.

Best regards,
Andy

Dear Frank,

I have another question. What I doing, What can I do to add periodicity of function. It is necessary that the values ​​of function repeated from year to year.

Best regards,
Andy

You could perhaps set the time to years, and subtract floor(t) from t. Or use if statements to shift the fucntion by a year when needed.
But by far the easiest solution is to export your table, and create the full one for all the years you have in excel for instance.

Best regards,
Frank

Dear Frank,

I think, what I do it of last way. Thank you!

P.S.: Can I write you an pvivate messange if i have others questions?

Best regards,
Andy

Dear Andy,

good to hear that it works now.

Private email would be via support. Otherwise it is better to use the forum for these type of questions.

Best regards,
Frank