[ahmmedshakil]

Hi,
I am trying to use the following boundary condition with groovyBC:
k*dT/dn = h*(T-Tinf)+(sigma*emissivity)*(T^4-Tinf^4)
where,
k= thermal conductivity=5.91 [W/mK]
h = heat transfer coefficient =12.4 [W/m2K]
Tinf =300K
emissivity=0.775
What happens in my case is that the simulation diverges after some time steps. Does anyone implemented this boundary condition in OpenFOAM? or any idea how to solve this problem???
Thanks in advance.

[gschaider]

Originally Posted by ahmmedshakil

Hi,
I am trying to use the following boundary condition with groovyBC:
k*dT/dn = h*(T-Tinf)+(sigma*emissivity)*(T^4-Tinf^4)
where,
k= thermal conductivity=5.91 [W/mK]
h = heat transfer coefficient =12.4 [W/m2K]
Tinf =300K
emissivity=0.775
What happens in my case is that the simulation diverges after some time steps. Does anyone implemented this boundary condition in OpenFOAM? or any idea how to solve this problem???
Thanks in advance.

Have you analyzed HOW it diverges? My guess is that it starts oscillating because it over/undershots Tinf. Try smaller timesteps.

[ahmmedshakil]

Thanks gschaider,
yes it's because of time steps. When I minimize the time steps the problem solved

[gschaider]

Originally Posted by ahmmedshakil

Thanks gschaider,
yes it's because of time steps. When I minimize the time steps the problem solved

OK. You can stabilize it by implementing a mixed boundary with TInf as the Dirichlet-term (that would avoid overshooting). The fractionExpression is to be calculated according to the heat-flux