[xiao]

I posted the question some time ago but did not get any reply ... so I reformulated it and posting it again. I hope someone with the experience could give me some hints. Thanks!

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The question is: how to "AUTO-WRITE" a field of type "scalarField" to a file, just in the same way as other fields like "p", and "U"?

I saw the example code in "spray" where a "volScalarField" is set up by reading from a file, or by construction from existing "volScalarField", but in my case, I don't have any existing field of the same type and I don't have any boundary conditions for this field.

I am doing particle-fluid interaction simulation, and in each time step, I calculate the solid volume fraction, and I want it to write itself to a file in the same way as "p" and "U". The gamma field has a value at each cell, no bounary condition or boundary field. HrV said in a post two years ago that it is a "bad idea" for construct a "volScalarField" from a "scalarField".
So... which way should I go in order to achieve this? Could someone give me some brief hint or pointer?

Thanks very much!

Heng