A33. propagation along a channel


The purpose of this test is to verify the influence of diffraction for waves propagating along a channel. The amplitude of the waves decays in axial direction due to loss of energy in lateral direction. The waves computed by Swan are Compared with an analytical solution taken from Booij (1981). This analytical solution was validated by measurements, see Booij (1981). The axis of the channel is in N-S direction.

At the Southern boundary an incident wave field is assumed which propagates from the Southern boundary in N direction. The peak period is 10 s.

In the analytical solution the amplitude along the axis is constant. Computed values for Hs along the axis are compared with the analytical results.

3 cases are considered:

A33a
Swan without diffraction with standard grid orientation
A33b
Same with oblique grid
A33c
Computation with diffraction on a standard grid

The highest panel shows the decay of Hs along the channel. It is seen that diffraction enhances the decay. Diffraction in Swan does not give enough decay if compared with the analytical solution.
The second panel shows the graphs of Hs computed on a cross-section; in this case there is no comparison with analytical results.

References

N. Booij (1981)
Gravity waves on water with non-uniform depth and current, PhD thesis, Delft University of Technology.

© 2012: Nico Booij