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Implement advective term in a UDS scalar

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Old   March 2, 2018, 07:37
Default Implement advective term in a UDS scalar
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Stavros Rafail Fostiropoulos
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Hello, I am trying to set up a uds in fluent in order to customize the energy equation. For simplicity, I do my tests in a singlephase flow, which is heat transfer inside a channel. The scalar quantity chosen is temperature. After initialising the temperature profile with a single value 373K throught my domain, I impose a BC at the inlet with higher temperature than 373K and a velocity value. I cancel the diffusion term, in order to test only the transient and advective term. In my test I activate both my Uds and Fluent Energy equation in order to compare the outcome of the simulation. Using the default option of Fluent for the advective term (mass flow rate in Define Scalar) I obtain exactly the same results in my Uds scalar profile and temperature profile computed by Fluent energy equation. However, when I hook a Udf (DEFINE_UDS_FLUX) where I return the F_FLUX, results are slightly different. I expected that the results should be exactly the same. Could you give me any insight into that issue? Thank you very much!
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define_uds_flux, f_flux

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