Scalar Transport values too large

zobekenobe · May 23, 2018, 14:10

I am trying to solve the simple channel flow with a UDS defined for solute concentration in the flow.

I have used UDF macros to define the boundary conditions and the diffusivity, density and viscosity.

I am using the mass flow rate for the convective flux
and don't have a source term.

The solution converges but the value of the UDS is extremely high (10^7) and the value grows extremely fast (within 5-10 iterations).

Can anyone suggest any checks or ways to figure the source of the problem.

I strongly feel there is a problem with the UDF but everything seems really fine.

pakk · May 23, 2018, 17:18

Maybe you made a udf that generates conditions for which those large values are a solution. If you don't show your udf, it is hard to say if it has a problem...

zobekenobe · May 28, 2018, 12:21

Hi Pakk,

It took me a while too clean the code and have in some documentation (though minimal).

below is the link where you can have a look

https://github.com/zobekenobe/UDS-Flux.git

Please have a look and share your insights.

Looking forward to your reply.

Thanks

May 23, 2018, 14:10	Scalar Transport values too large	#1
zobekenobe Member zobekenobe Join Date: Mar 2009 Location: Dublin, Ireland Posts: 72 Rep Power: 17	I am trying to solve the simple channel flow with a UDS defined for solute concentration in the flow. I have used UDF macros to define the boundary conditions and the diffusivity, density and viscosity. I am using the mass flow rate for the convective flux and don't have a source term. The solution converges but the value of the UDS is extremely high (10^7) and the value grows extremely fast (within 5-10 iterations). Can anyone suggest any checks or ways to figure the source of the problem. I strongly feel there is a problem with the UDF but everything seems really fine.

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May 23, 2018, 17:18		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 27	Maybe you made a udf that generates conditions for which those large values are a solution. If you don't show your udf, it is hard to say if it has a problem...

May 28, 2018, 12:21		#3
zobekenobe Member zobekenobe Join Date: Mar 2009 Location: Dublin, Ireland Posts: 72 Rep Power: 17	Hi Pakk, It took me a while too clean the code and have in some documentation (though minimal). below is the link where you can have a look https://github.com/zobekenobe/UDS-Flux.git Please have a look and share your insights. Looking forward to your reply. Thanks