A12. Period with changing current velocity
As in A11 we consider an infInite domain with a uniform wave field. An initial spectrum is given (narrow both in σ and in θ). In test A12 the depth is constant (=5 m), and the current velocity is varied as function of time. It is seen from theory that wave number and direction of the wave field have to remain constant. A table is written giving depth, current velocity, wavelength, direction and period (both relative and absolute) as function of time.
The analytical solution for this case is:
(where T is absolute period).
Since Swan uses a spectrum formulated in terms of ; there is transport of energy in -direction; there is also transport in . There may be a change in the shape of the spectrum due to numerical inaccuracies. Plot file A12.plt shows (absolute) period, wavelength and direction as function of current velocity (the component in y-direction since the direction of the wave field is 90o.
1 case is considered: