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Residual value Oscillations

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Old   December 7, 2017, 11:30
Default Residual value Oscillations
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Siddhartha Desu
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All,

I am simulating a box barge in head waves condition (first order waves) to study the forces, and wave profiles in the wake.

I am simulaiting fixed barge of L=2m, B=1m, T=0.5m in a tank of (L,W,H = 30,30,20). Using first order waves (wavelength= L). I am using wave damping length of 2L from the boundaries. My BC's are Velocity inlet for
Inlet, Bottom, Top , Pressure outlet for Outlet, Symmetry for sides. I am using about 4.8m cells for this condition.

My problem is with the residuals, They are dying down as more physical time passes but the oscillations are not. Is this acceptable? Could anyone suggest what the problems might be?

Happy to provide more info. Thanks in advance!
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Old   December 7, 2017, 13:34
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I believe the residuals may oscillate however they still appear rather high. They should drop 3 to 4 orders of magnitude.

Have you tried reducing the cell size?
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Old   December 7, 2017, 15:41
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Can you recommend me what the best size for the tank is ?

Right know my tank is 15 times the length of the barge. Thus I am not able to reduce the cell size much (current cell size = 0.07m). If I reduce further I am getting too many cells to compute effectively (about 15m or more cells).

On the other hand when I was working in a reduced tank size (10 times the length of the barge), I am getting so much reflections from the boundaries and the waves are dying down before the simulation is ending.
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Old   December 8, 2017, 03:58
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Ashok Chaudhari
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Quote:
Originally Posted by Siddhartha1993 View Post
Can you recommend me what the best size for the tank is ?

Right know my tank is 15 times the length of the barge. Thus I am not able to reduce the cell size much (current cell size = 0.07m). If I reduce further I am getting too many cells to compute effectively (about 15m or more cells).

On the other hand when I was working in a reduced tank size (10 times the length of the barge), I am getting so much reflections from the boundaries and the waves are dying down before the simulation is ending.
Which mesher are you using? also physics models?
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Old   December 8, 2017, 04:10
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Trimmed cell mesher and prsim layer mesher and surface remesher.

Models: Implicit Unsteady, Eulerian Multiphase, K-Epsilon Turbulence, Volume of Fluid (VOF), VOF Waves, Gravity,Cell Quality Remediation.
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