# Defining Evaporation - A How To Guide.

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 July 25, 2005, 04:59 Defining Evaporation - A How To Guide. #1 Owen Guest   Posts: n/a A search through this forum and the Fluent UDF guide has left me with the idea that modelling evaporation isn't going to be a simple process. I am seeking to model the evaporation from a free surface specifically to investigate the effect of wind speed on evaporation rate and thus cooling of the vessel. When writing the UDF to define mass/heat transfer at the interface (using VOF model) I'm stuck trying to define the cell/face interface thread - so the gas is being generated through the bulk of the fluid instead of only on the surface. Please inform how evaporation can be handled with a UDF.

 July 25, 2005, 09:56 Re: Defining Evaporation - A How To Guide. #2 Joey Guest   Posts: n/a Hi, Owen I want to simulate evaporation like this later this year. Can you tell me the formula of the mass/heat transfer during the evaporation process or just give me some information about the material required? If you like, there is my email address. Thanks a lot! I will looking for the method on how to chase the interface of water/vapor.If there is any information I will tell you about it. And now I have an idea about this, maybe it is just an approximation. You can define two source terms for the water and vapor continuation equation and one for energy equation.In the DEFINE macro you can judge the whether a cell is interface cell, if it is a inter face cell return the source if not return 0. How to judge whether the cell is a interface cell? Two process: the first:if(( C_VOF(c,pt[0])*C_VOF(c,pt[1]*..) != 0)/*none of C_VOF(c,pt[i]is zero)*/ the cell is a interface cell; and then in the second process: loop over every face of the cell to judge whether there is an adjacent cell in which the VOF(c1,pt[0])=0(no water in the cell),if so it is an interface cell. I think this could help before you find the proper method of chasing the interface. I am not familiar with the VOF model. Joey

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