Fluent Neumann boundary Condition by UDS UDF

Xuxu · September 28, 2023, 00:04

Hello,
I create a scalar transport equation using UDS in Fluent and I need to implement Neumann boundary, which can be expressed as Fig1.

Moreover, the equation I solved is needed to calculate for many times since the deltaT is changed by me, that is, after flow equation solved once, my equation gets results(velocity pressure) from flow field and the deltaT is changed into 1/10 of the flow_deltaT.
However, the DEFINE_ADJUST is execute before the calculation of flow fields. Once my equation begins to solve, the DEFINE_ADJUST won’t work, that is, since my equation is needed to be solved 10 times in one flow time-step, in the first calculation of my equation, it works; but in the second calculation, it won’t work since the DEFINE_ADJUST is only execute once. Simply, if DEFINE_ADJUST can be used, how to maintain it during many calculation within one flow time-step.

Xuxu · October 4, 2023, 11:02

Hello,
does anyone have any ideas?

September 28, 2023, 00:04	Fluent Neumann boundary Condition by UDS UDF	#1
Xuxu New Member Join Date: Sep 2023 Posts: 7 Rep Power: 3	Hello, I create a scalar transport equation using UDS in Fluent and I need to implement Neumann boundary, which can be expressed as Fig1. Moreover, the equation I solved is needed to calculate for many times since the deltaT is changed by me, that is, after flow equation solved once, my equation gets results(velocity pressure) from flow field and the deltaT is changed into 1/10 of the flow_deltaT. However, the DEFINE_ADJUST is execute before the calculation of flow fields. Once my equation begins to solve, the DEFINE_ADJUST won’t work, that is, since my equation is needed to be solved 10 times in one flow time-step, in the first calculation of my equation, it works; but in the second calculation, it won’t work since the DEFINE_ADJUST is only execute once. Simply, if DEFINE_ADJUST can be used, how to maintain it during many calculation within one flow time-step.

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October 4, 2023, 11:02		#2
Xuxu New Member Join Date: Sep 2023 Posts: 7 Rep Power: 3	Hello, does anyone have any ideas?