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nonh=1 and oblique waves

MM
Marco Miani, modified 5 Years ago.

nonh=1 and oblique waves

Wind Posts: 40 Join Date: 4/1/14 Recent Posts
Dear XB Developers,

The non-hydrostatic manual for X-Beach states:
For application in X-Beach we are only interested in the velocity component perpendicular to the boundary and we will therefore ignore the v components.


Is there any way of including a v component??
This would, in essence, contemplate the possibility of steering the waves at the boundary, i.e sending in oblique waves.

The present limitation imposes that the angle of attack is and must be 90 degrees. That limitation is very stringent.

Thank you for considering my question.
Cheers,
M
MM
Marco Miani, modified 5 Years ago.

RE: nonh=1 and oblique waves

Wind Posts: 40 Join Date: 4/1/14 Recent Posts
A brief follow up:



My apologies for not having paid attention to what follows, before posting the previous message-

The same manual quoted in my previous message, states:

Example 2: Vector data
If the velocity and/or free surface signal varies in both space and time along the boundary
(for instance for obliquely incident waves) the velocity/surface elevation along the entire boundary
needs to be specified at every moment in time. If we would only have 3 grid points
along the boundary in the lateral y-direction the specified boundary file could read:

Example 1: Vector
vector
3
t U Z
%t    u    u     u         z     z    z
0.0    0.000   0.000   0.000   0.000   0.000   0.000
1.0    0.005   0.004   0.003   0.100   0.090   0.080
2.0    0.010   0.009   0.008   0.200   0.190   0.180
3.0    0.005   0.004   0.003   0.100   0.090   0.090
4.0    0.000   0.000   0.000   0.000   0.000   0.000
Here we first specify the velocity as it is listed first under the variables.
Furthermore a value for each point along the boundary is specified.
At t=2 the velocity U_1,2 is set to 0.009 m/s and the surface
elevation at the same position to h_1,2 = 0.19 m


My Questions:

Should the number of prescribed points (i.e., couples of u and z) equal the number of grid point along the open boundary? Or does XBEACH know the meaning of interpolation?

Assuming a rectangular grid, and assuming on of the sides is on land: the remaing 3 are 'open boundaries'. Can all boundaries be forced simultaneously? Or just one? Or just one per file?

Has anyone ever dealt with this problem before (oblique waves, and nonh=1)?

Thanks.
Robert McCall, modified 4 Years ago.

RE: nonh=1 and oblique waves

Wind Posts: 83 Join Date: 3/24/11 Recent Posts
Hi Marco,

You can send in oblique waves with just u and zs, v is computed as an unknown from the two other variables. Try using spectral wave conditions (e.g., instat = jons) with an oblique wave angle and you should be able to see how XBeach deals with this.

Second, your other questions:

- No, XBeach doesn't interpolate, so you need to specify for all ny+1 offshore boundary points.
- No, you can only apply wave forcing on the offshore boundary of the model.

Hope this helps,

Robert
DD
dedede dede, modified 17 Days ago.

RE: nonh=1 and oblique waves

Capillary Posts: 4 Join Date: 3/22/20 Recent Posts
Here we first specify the velocity as it is listed first under the variables 

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