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Courant number is spiking in very small section

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Old   March 8, 2024, 01:20
Default Courant number is spiking in very small section
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Desh
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Hi All,

I am running a venting event in 2D wedge domain with rhoPimpleFoam in OF10.

Please see the attached figure.

My fluid domain is roughly 0.7 m (height) x 0.1 m (radius) of a wedge.

From the bottom surface of the wedge I've assigned my outlet.

The question is solver is choosing very small time stepping (1E-9/10). Reason for this is only few cells Co no is reaching to 1 whilst all the rest remains under 1e-8 or so.

My mesh is clean, and no errors at all..

How can I avoid this few cells Co being increased so I can increase my overall time stepping ?

Any insights are highly appreciated.

Thank you.
Dasith
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Old   March 8, 2024, 01:23
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Sorry forgot to attached the figure
Attached Images
File Type: jpg maxC0.jpg (88.2 KB, 17 views)
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Old   March 8, 2024, 09:27
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Quote:
Originally Posted by dasith0001 View Post
Sorry forgot to attached the figure

Looks like this occurs where there is a significant jump in cell spacing. Try to keep changes in cell size to within 20%. This means you would need to apply some simpleGrading.
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Old   March 10, 2024, 17:12
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Quote:
Originally Posted by joshwilliams View Post
Looks like this occurs where there is a significant jump in cell spacing. Try to keep changes in cell size to within 20%. This means you would need to apply some simpleGrading.

Hi,

Thank you for your reply. Apologies for the misinterpretation of the problem.

The mesh in the figure is only one iterations of me trying to avoid the Co spike.

I tried simpleGrading to make the mesh for uniform/refine/course basically everything. Nothing works.

However that boundry has a pressure gradient of delataP = 200MPa- 0.1MPa

Following are the pressure and velocity boundary conditions I am using;

PHP Code:
internalField   uniform 200000000;

boundaryField
{

    
outlet
    
{
            
type              totalPressure;
            
p0                uniform 101325;
            
value             uniform 101325;
    }

PHP Code:
    outlet
    
{
        
type            pressureInletOutletVelocity;
        
inletValue      uniform (0 0 0);
        
value           uniform (0 0 0);
    } 
I am running out of options here.
Thank you
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