Particles unstable with a type of re-circulation

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Particles unstable with a type of re-circulation

Postby vivekfrancis139 on Wed Nov 01, 2017 6:31 am

Hi,

I'm using a piston type wavemaker for generating waves inside a box. The piston is positioned at a particular distance from the front of the left wall of the box.

What I observe is that the particles are unstable and exhibit a form of re-circulation within the domain. In order to fix this I added a settling or damping time before the wavemaker is moves but the phenomenon still persists. Immediately after starting the simulation the fluid particles in the region between the left wall and the back side of the wavemaker starts experiencing a drop in the water level. Meanwhile, the particles on the other side of the wavemaker have this type of re-circulation type flow. Then when the damping period is crossed, the wavemaker moves generating a wave. But the generated wave elevations carry these spurious harmonics.

The Case file that I'm using have the following details:
Kernel: cubic
Time-stepping: symplectic
Denisty filter: Shepard
Kernel correction: none
Viscosity treatment: laminar + SPS
Viscosity value: 1.0e-6
Maximum depth to calculate B: 0.3
Coeff. of speed of sound: 20
Boundary condition: REPULSIVE
Wall viscosity value for repulsive bc: 8.0e-5
Initial fluid particle structure: BCC
Initial conditions: Fill square shaped region
Correct pressure at boundaries: 0
CFL: 0.5
h coefficient value: 1.3
Riemann solver: None

I really look forward to your answers. Any suggestion would be really appreciated.
Attachments
Case16_anim.0000.png
Initial setup
Case16_anim.0000.png (22.36 KiB) Viewed 45 times
Case16_anim.0023.png
Just before wavemaker begins movement (at end of damping time given) (also notice drop in water surface level)
Case16_anim.0023.png (45.87 KiB) Viewed 45 times
Case16_anim.0060.png
During piston movement
Case16_anim.0060.png (71.82 KiB) Viewed 45 times
vivekfrancis139
 
Posts: 3
Joined: Fri Oct 07, 2016 7:50 am

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