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-   -   can i use field functions in star ccm for this? (https://www.cfd-online.com/Forums/siemens/56299-can-i-use-field-functions-star-ccm.html)

 stu October 4, 2007 07:23

can i use field functions in star ccm for this?

Hi,

I am modelling a number of bio-heat sources confined in a room.

I want each each source to respond to local air velocity and temperature conditions by regulating heat flux, i.e. thermoregulation.

If I have a simple equation to describes this response, can I prescribe it as a heat flux boundary condition with the use of field functions, or must I attempt some user coding.

Also would I need to run a transient simulation.

Looking forward to any suggestions, Regards, stu

 Aeron October 8, 2007 20:59

Re: can i use field functions in star ccm for this

This should be possible in STAR-CCM+ using field functions. Review the help section in CCM+ for examples on field functions. Set up a few easy ones as models, for example, start with pressure at the surface (velocity won't work for this) and tie the pressure to some factor of cooling or rate of heat transfer. Field functions examples are often only single lines. However, it may not be clear in their examples, but they can be nested into multiple loops. Or generate several stand-alone field functions based on others you have made. This is a little more cumbersome, but it still gets the job done.

Something else to consider is to create a geometry where the bio sources are solids, except for a small sphere or cube subtracted from inside the solid. The boundary created by subtracting the sphere can used as your source, then the solid heats/cools based on the internal boundary and the airflow going over the outside. If the value at the inside of the hollow (located inside the solid bio object, animal, plant, etc. whatever it is) is a good starting condition, then this approach is the more physical one.

 stu October 12, 2007 15:50

Thanks Aeron; I have one more question

Thanks Aeron for your interesting suggestions,

I have did what you said and designed a hollow sphere; however I'd like its thermal conductivity to vary as a function of local temperature.

Is it possible to use field functions to reference a suitable cell, or group of cells for this temperature, i.e. an average temperature taken from a group of cells in the ambient, a little away from influence of the heat source.

There is very little documentation on user defined field functions, and none on nested loops, which I'd find helpful.