Boundary Condition

Nitheesh PC · April 20, 2016, 07:25

Hai Friends...............
Iam doing transient analysis during chill down process.Initially liquid nitrogen is flowing through the pipe.Boundary Condition at the interface of liquid and pipe is taken as coupled.Next step provide a polyerethane insulation to the pipe.What is the boundary condition at the interface of pipe and insulation.Pl help?

LuckyTran · April 20, 2016, 11:01

There are no boundary conditions per se at an interface. At an interface you only have interface conditions (matching principles): i.e. energy balance (the thermally coupled condition), no-slip (parallel velocities equal), impenetrable/impermeable condition (zero normal velocity) and so forth.

Nitheesh PC · April 20, 2016, 12:31

what is floating point exception?
while running the case in ansys fluent i face the problem

reversed flow in 1 faces on pressure-inlet 12.
# Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps!
temperature limited to 5.000000e+03 in 7 cells on zone 8 in domain 1
temperature limited to 5.000000e+03 in 23 cells on zone 10 in domain 1

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Error at host: floating point exception

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 193168 cells

Nitheesh PC · April 20, 2016, 12:40

For without insulation inner pipe have thermal condition as coupled and outer pipe have mixed
For with insulation inner pipe have coupled,outer pipe have coupled ,insulation outer surface have mixed conditions.Is it right?

LuckyTran · April 20, 2016, 14:06

Floating point exception (also known as a stack overflow) is an error that occurs when you try to do something with a floating point number that is impossible (like dividing by zero).

It is my personal opinion that the user should always know their boundary conditions because that is part of the problem definition. To solve any problem you must have a domain, boundary conditions, initial conditions, and physics. Otherwise, any work that you do is meaningless because you do not even know what it is you are simulating.

April 20, 2016, 07:25	Boundary Condition	#1
Nitheesh PC New Member NITHEESH P C Join Date: Apr 2016 Posts: 3 Rep Power: 10	Hai Friends............... Iam doing transient analysis during chill down process.Initially liquid nitrogen is flowing through the pipe.Boundary Condition at the interface of liquid and pipe is taken as coupled.Next step provide a polyerethane insulation to the pipe.What is the boundary condition at the interface of pipe and insulation.Pl help?

April 20, 2016, 12:31	floating point exception	#3
Nitheesh PC New Member NITHEESH P C Join Date: Apr 2016 Posts: 3 Rep Power: 10	what is floating point exception? while running the case in ansys fluent i face the problem reversed flow in 1 faces on pressure-inlet 12. # Divergence detected in AMG solver: temperature -> Increasing relaxation sweeps! temperature limited to 5.000000e+03 in 7 cells on zone 8 in domain 1 temperature limited to 5.000000e+03 in 23 cells on zone 10 in domain 1 Divergence detected in AMG solver: temperature Divergence detected in AMG solver: temperature Error at host: floating point exception turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 193168 cells

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April 20, 2016, 11:01		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	There are no boundary conditions per se at an interface. At an interface you only have interface conditions (matching principles): i.e. energy balance (the thermally coupled condition), no-slip (parallel velocities equal), impenetrable/impermeable condition (zero normal velocity) and so forth.

April 20, 2016, 12:40		#4
Nitheesh PC New Member NITHEESH P C Join Date: Apr 2016 Posts: 3 Rep Power: 10	For without insulation inner pipe have thermal condition as coupled and outer pipe have mixed For with insulation inner pipe have coupled,outer pipe have coupled ,insulation outer surface have mixed conditions.Is it right?

April 20, 2016, 14:06		#5
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,675 Rep Power: 66	Floating point exception (also known as a stack overflow) is an error that occurs when you try to do something with a floating point number that is impossible (like dividing by zero). It is my personal opinion that the user should always know their boundary conditions because that is part of the problem definition. To solve any problem you must have a domain, boundary conditions, initial conditions, and physics. Otherwise, any work that you do is meaningless because you do not even know what it is you are simulating.