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icoFoam Blowup at Farfield Boundary

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Old   February 27, 2022, 01:19
Default icoFoam Blowup at Farfield Boundary
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Daniel Dotson
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Hello,


I am running a transient Karman-Trefftz airfoil case with icoFoam.


Re: 10000
α: 5
Grid Topology: O
Number of Cells: ~1000000 (almost entirely perfect squares)

Δt: 0.0004

Domain Radius: 20c
Wall BC: zeroGradient Pressure, noSlip Velocity

Farfiled BC: fixedValue Pressure, fixedValue Velocity



I know this isn't the ideal setup for this problem but I am just trying to experiment. The max Courant number starts off a bit high for a few steps near the LE and TE where the cells are smallest, but it quickly settles into about 0.8 as the boundary layer grows. On the downstream boundary, a wavy artifact in the velocity field starts off barely visible and then gradually grows until the solution blows up.


t=0.4s
t04.png


t=6.0s
t6.png


t=7.6s
t76.png


Is there something wrong with my boundary conditions?
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Old   February 27, 2022, 09:07
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Daniel Dotson
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I managed to stabilize it by changing the farfield boundary conditions to freestreamVelocity and freestreamPressure.
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airfoil, blowup, boundary conditions, external, farfield

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