Learning Forum

[Mahmoud Nassar]

Hi,
I'm currently working on simulating the propagation of a 2D wave inside a tank using VOF. Here are the parameters:

• The wave has a height of 0.5m and a length of 5.5m.
• The depth is set to -6m, and the free surface is at x = y = 0.
• The domain extends from -15m to +15m in the x-direction and from -6m to 10m in the y-direction.
• Boundary conditions: velocity inlet on the left, pressure outlet on the upper and right boundaries, and a wall at the bottom. The numerical beach is activated to prevent wave reflections.

I'm trying to monitor the wave height at different positions, such as at the right boundary and x = -10m. To do this, I created a line at the desired positions and then generated an isosurfaces (water fraction) based on these lines. I set the monitors on the mesh, the Y-coordinate.

Here are my questions:

1. Why does the water level change with the wave? In other words, why isn't the wave oscillating around the free surface, especially since I'm using first-order Airy?

2. Why isn't the wave height consistent with what I've set in the setup, particularly at the inlet and positions very close to it? For example, if I set the wave to be 0.5m, I'm getting readings of 0.45m or even less.

3. Why is the wave height curve not smooth? Instead, it appears as a steep curve.

I've tried various approaches, including different numerical schemes (SIMPLE and PISO), adjusting distances above the free surface, changing time steps, using laminar and turbulent models, and altering wave conditions, but nothing seems to resolve these issues.

I've also looked into discussions on wave generation techniques but haven't been able to find a solution.

Could you please provide some advice on how to address these issues?

Thank you.

 

 

• 

[Rob]

The inlet report may be picking up the cell centre value, is the cell height 5cm on the boundary? 

Not sure what the domain report is, but if you've only run 2s and the domain is 30m long there's a good chance the solution isn't anywhere near the equilibrium state.