UDS boundary for pressure-out

Lee 小亢 · May 23, 2018, 11:00

Hi~every one,
I found a problems in my work and want to discuss with you. I calculated a uds in my case so I need to set the boundary condition for my outlet. Tne quesition is how I set the boundary condition? Here are two ways to set the boundary condition:specified flux and specified value...I am confused about it. Is the value of UDS at the outlet I am going to calculate? Why I need set it?

AlexanderZ · May 23, 2018, 21:58

yes, that is the value of your UDS (if you use fixed value option)
to calculate UDS you must define source and boundary condition, to get the distribution field in domain.

Let suppose, you have source and only flux = 0 everywhere, in that case you UDS may get any value

I hope this will help you

best regards

Lee 小亢 · May 24, 2018, 07:56

thanks AlexanderZ, I konw what you means. But I want to ask a question like this: If there is one inlet and one outlet in my geometry.Fluid material is liquid. The UDS transport equation includes transient term（by default）, source term (user defined ) , Convective term（flux function is mass flow rate） and diffusion term (I defined the diffusion coefficient）. I set the fix value of the UDS at the inlet.All the other boundary condition is standard wall and UDS bondary condition is fix value of 0. I mean this condition I need set the bondary condition for the UDS at the outlet? Isn't it computering by the transport equation?
best wishes

May 23, 2018, 11:00	UDS boundary for pressure-out	#1
Lee 小亢 New Member Lee Join Date: Feb 2018 Posts: 12 Rep Power: 8	Hi~every one, I found a problems in my work and want to discuss with you. I calculated a uds in my case so I need to set the boundary condition for my outlet. Tne quesition is how I set the boundary condition? Here are two ways to set the boundary condition:specified flux and specified value...I am confused about it. Is the value of UDS at the outlet I am going to calculate? Why I need set it?

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May 23, 2018, 21:58		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	yes, that is the value of your UDS (if you use fixed value option) to calculate UDS you must define source and boundary condition, to get the distribution field in domain. Let suppose, you have source and only flux = 0 everywhere, in that case you UDS may get any value I hope this will help you best regards

May 24, 2018, 07:56		#3
Lee 小亢 New Member Lee Join Date: Feb 2018 Posts: 12 Rep Power: 8	thanks AlexanderZ, I konw what you means. But I want to ask a question like this: If there is one inlet and one outlet in my geometry.Fluid material is liquid. The UDS transport equation includes transient term（by default）, source term (user defined ) , Convective term（flux function is mass flow rate） and diffusion term (I defined the diffusion coefficient）. I set the fix value of the UDS at the inlet.All the other boundary condition is standard wall and UDS bondary condition is fix value of 0. I mean this condition I need set the bondary condition for the UDS at the outlet? Isn't it computering by the transport equation? best wishes