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-   -   define mass transfer - define source (http://www.cfd-online.com/Forums/fluent/42265-define-mass-transfer-define-source.html)

 greg September 8, 2006 11:27

define mass transfer - define source

hi I have a probblem with boiling (defined by DEFINE_MASS_TRANSFER or DEFINE_SOURCE) using standard (provided by Fluent) tutorials - means udf`s from I can get boiling of water (both in VOF and Mixture model) but.... the temperatures are stupid. In liquid pase temperature is OK but in gas phase it reach maximum or minimum temperature (from temp. on beginning = 350K to 1K or 5000K which are max and min. temperatures in FLUENT). Do you happen to know what to do? Meybe you had the same problem. regards g

 gaza July 14, 2016 12:48

FLUENT will automatically include the terms needed to model mass transfer in all relevant conservation equations. Another option to model mass transfer between phases is through the use of user-defined sources and their inclusion in the relevant conservation equations. This approach is a more involved but more powerful, allowing you to split the source terms according to a model of your choice.

FLUENT
provides a DEFINE_MASS_TRANSFER that you can use to input models for different types of mass transfer, e.g. evaporation, condensation, boiling, etc. Note that when using this UDF, FLUENT will automatically add the source contribution to all relevant momentum and scalar equations. This contribution is based on the assumption that the mass "created'' or "destroyed'' will have the same momentum and energy of the phase from which it was created or destroyed.

If you would like to input your source terms directly into mass, momentum, energy, or scalar equations, then the appropriate path is to use UDFs for user-defined sources for all equations, rather than the UDF for mass transfer.

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