Floating Point error

egwuab · July 9, 2014, 15:32

I am running a simulation of a wind through a truck with trailer.
I set up the simulation as a wind tunnel test, the flow is from right to left. 4 symmetry plane for ground, top, front, and behind.

I'm using Constant Density, Segregated Flow, turbulent k-e model.
after 136 iterations, i got this message error:

"Turbulent viscosity limited on 4 cells in Region 1
A floating point exception has occurred: floating point exception [Overflow]. The specific cause cannot be
identified."

Do you mind to help me figuring out why this is happening?

me3840 · July 9, 2014, 20:02

Check that your BC turbulence quantities are reasonable.

Generally though this error indicates a mesh problem. Ensure your mesh is fine enough in the wake region and your wall y+ values are good. Is this a scaled model? How big is your mesh? For a full vehicle it should be somewhere around 60M cells.

It sounds like you're trying to run a steady-state simulation. This will be difficult to converge with such a large separated wake. You should at least look into an unsteady solution or using DES.

egwuab · July 9, 2014, 23:48

Hi me3840,

My model is not scaled, its 20m long and 2.5m width.
Yes, im running in steady state solution.
I didn't really mesh is too much its only 2.5M cells.
Here is my mesh, is it too coarse ?
http://s29.postimg.org/njmi3bs1z/truck2.png

Thank you !!

July 9, 2014, 15:32	Floating Point error	#1
egwuab New Member Erik Join Date: May 2014 Posts: 23 Rep Power: 12	I am running a simulation of a wind through a truck with trailer. I set up the simulation as a wind tunnel test, the flow is from right to left. 4 symmetry plane for ground, top, front, and behind. I'm using Constant Density, Segregated Flow, turbulent k-e model. after 136 iterations, i got this message error: "Turbulent viscosity limited on 4 cells in Region 1 A floating point exception has occurred: floating point exception [Overflow]. The specific cause cannot be identified." Do you mind to help me figuring out why this is happening?

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July 9, 2014, 20:02		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Check that your BC turbulence quantities are reasonable. Generally though this error indicates a mesh problem. Ensure your mesh is fine enough in the wake region and your wall y+ values are good. Is this a scaled model? How big is your mesh? For a full vehicle it should be somewhere around 60M cells. It sounds like you're trying to run a steady-state simulation. This will be difficult to converge with such a large separated wake. You should at least look into an unsteady solution or using DES.

July 9, 2014, 23:48		#3
egwuab New Member Erik Join Date: May 2014 Posts: 23 Rep Power: 12	Hi me3840, My model is not scaled, its 20m long and 2.5m width. Yes, im running in steady state solution. I didn't really mesh is too much its only 2.5M cells. Here is my mesh, is it too coarse ? http://s29.postimg.org/njmi3bs1z/truck2.png Thank you !!