Pls help imp!! Convergence of natural convection model

laura_c · May 9, 2013, 15:25

Hi guys, I am modelling natural convection - laminar - steady state.

the model is a box with 2 inlets and 1 outlet and a heater inside.

the residuals are steady but high and it is not converging. i tried to lower the under relaxation values but still residuals are high. I read that natural convection usually converges in transient simulations and that it is frequent that does not converge in steady state.

is it wrong to keep this model and use it? will it give me wrong values?

pls help...my deadline is in a week and i m having strong doubts about this!!

thanks

rajeshkunwar · May 15, 2013, 04:47

Hi, Laura

Yes there are issues with steady state simulation of natural convection problem. You should have a good mesh and right boundary condition to get convergence. check your boundary conditions.

MachZero · May 15, 2013, 08:03

I know one of my coworkers was having a similar problem and had to not only solve it in transient, but had to slowly increase gravity from 0 to 10

May 9, 2013, 15:25	Pls help imp!! Convergence of natural convection model	#1
laura_c New Member Laura Join Date: Apr 2013 Posts: 15 Rep Power: 13	Hi guys, I am modelling natural convection - laminar - steady state. the model is a box with 2 inlets and 1 outlet and a heater inside. the residuals are steady but high and it is not converging. i tried to lower the under relaxation values but still residuals are high. I read that natural convection usually converges in transient simulations and that it is frequent that does not converge in steady state. is it wrong to keep this model and use it? will it give me wrong values? pls help...my deadline is in a week and i m having strong doubts about this!! thanks

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Superlinear speedup in OpenFOAM 13	msrinath80	OpenFOAM Running, Solving & CFD	18	March 3, 2015 05:36
Is it possible to model natural convection in a 2D horizontal model in fluent	caitoc	FLUENT	1	May 5, 2014 13:32
laminar or turbulent model for natural convection	ans281086	FLUENT	0	April 21, 2011 06:30
Natural Convection Problem - Helium	marzoa	STAR-CCM+	0	April 18, 2011 14:12
Approximate Mixing due to Natural Convection	Greg Perkins	Main CFD Forum	0	February 12, 2003 18:43

May 15, 2013, 04:47		#2
rajeshkunwar New Member Rajesh Kumar Join Date: Apr 2009 Posts: 25 Rep Power: 17	Hi, Laura Yes there are issues with steady state simulation of natural convection problem. You should have a good mesh and right boundary condition to get convergence. check your boundary conditions.

May 15, 2013, 08:03		#3
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 14	I know one of my coworkers was having a similar problem and had to not only solve it in transient, but had to slowly increase gravity from 0 to 10