Need help - Divergence in AMG solver - temperature

nareshzeeda1994 · March 28, 2018, 06:23

Hi all,,

I am doing dual stream heat transfer analysis of 3 heat exchangers which are put together under a single domain.

After modelling all the three heat exchangers under a single domain ( cuboid ), I mesh it. There are many contact regions created ( nearly 300 ). After that I mesh it. And I open it in fluent.

I turn on the energy equation and I gave the cell zone. In boundary condition, I gave the air in(velocity inlet) and air out(pressure outlet) for the domain. Now for coolant I'm not able t give the boundary condition since all are under interface so that mesh interface is created.

If I change the interface option to mass flow inlet, the solution is diverged and following error pops out.

" Divergence detected in AMG Solver - temperature"
"Temperature limited to 1.000000 in 22500 cells in domain 17"
"Floating point exception"

An if I delete all the contact regions, then also it is not working and the same errors pops out.

What should I do now ??? I have clean mesh and geometry.

Help me.

Thanks in advance...

patilyogesh · March 28, 2018, 09:07

reduce the Under relaxation factor for energy near 0.2 or reduce mesh skewness

nareshzeeda1994 · March 28, 2018, 09:54

Quote:

Originally Posted by patilyogesh

reduce the Under relaxation factor for energy near 0.2 or reduce mesh skewness

Thanks for your reply.

But the thing is that I tried this method by reducing the UDF energy to 0.6
Still it showed the same error.

Now my question is how to create a contact region for mesh interface ? Help me

patilyogesh · March 28, 2018, 10:07

in mesh with the help of new contact region, we can create contact or in solver with the help of mesh interface by selecting srg and their respective trg

nareshzeeda1994 · March 29, 2018, 04:45

Quote:

Originally Posted by patilyogesh

in mesh with the help of new contact region, we can create contact or in solver with the help of mesh interface by selecting srg and their respective trg

I'm new to ansys. first tell me what is srg and trg ??

If possible, send me tutorial if you have any.

Thanks.

patilyogesh · March 29, 2018, 09:27

watch this video https://www.youtube.com/watch?v=NPJImYibx48

March 28, 2018, 06:23	Need help - Divergence in AMG solver - temperature	#1
nareshzeeda1994 New Member Naresh Mahendran Join Date: Mar 2018 Posts: 22 Rep Power: 8	Hi all,, I am doing dual stream heat transfer analysis of 3 heat exchangers which are put together under a single domain. After modelling all the three heat exchangers under a single domain ( cuboid ), I mesh it. There are many contact regions created ( nearly 300 ). After that I mesh it. And I open it in fluent. I turn on the energy equation and I gave the cell zone. In boundary condition, I gave the air in(velocity inlet) and air out(pressure outlet) for the domain. Now for coolant I'm not able t give the boundary condition since all are under interface so that mesh interface is created. If I change the interface option to mass flow inlet, the solution is diverged and following error pops out. " Divergence detected in AMG Solver - temperature" "Temperature limited to 1.000000 in 22500 cells in domain 17" "Floating point exception" An if I delete all the contact regions, then also it is not working and the same errors pops out. What should I do now ??? I have clean mesh and geometry. Help me. Thanks in advance...

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March 28, 2018, 09:07		#2
patilyogesh New Member PATIL YOGESH KASHINATH Join Date: Mar 2018 Posts: 8 Rep Power: 8	reduce the Under relaxation factor for energy near 0.2 or reduce mesh skewness

March 28, 2018, 10:07		#4
patilyogesh New Member PATIL YOGESH KASHINATH Join Date: Mar 2018 Posts: 8 Rep Power: 8	in mesh with the help of new contact region, we can create contact or in solver with the help of mesh interface by selecting srg and their respective trg

March 29, 2018, 09:27		#6
patilyogesh New Member PATIL YOGESH KASHINATH Join Date: Mar 2018 Posts: 8 Rep Power: 8	watch this video https://www.youtube.com/watch?v=NPJImYibx48