A53. Non-stationary convergence test

It was demonstrated by Claessens et al. (??) that in case of a rapidly changing wind velocity the results of Swan are very sensitive to numerical choices such as time step and number of iterations per time step.
In their test the wind velocity changed from 8 m/s to 18 m/s in one hour. They simulated a front passage.
In this series of tests we simplify even further. We assume a homogeneous situation, represented by only one computational point. Claessens et al. do not give the depth in their tests, we use a (uniform) depth of 10 m.

The graphs in file A53.plt Compare a number of numerical settings.

8 cases are considered:

A53a
Δt = 20 minutes, 1 iteration per time step
A53b
Δt = 20 minutes, 2 iterations per time step
A53c
Δt = 20 minutes, 4 iterations per time step
A53d
Δt = 10 minutes, 2 iterations per time step
A53e
Δt = 5 minutes, 2 iterations per time step
A53f
Δt = 2 minutes, 2 iterations per time step
A53g
Δt = 1 minute, 2 iterations per time step
A53h
Δt = 10 minutes, 2 iterations per time step, relaxed limiter (=0.2)

References

Claessens, E.J., J.P. de Waal, H.C. van Twuiver and M. Bottema (??)
The application of a coupled wind, waterlevel and wave model in warning system against flooding, Directorate-General of Public Works and Water Management, Institute for Inland Water Management and Waste Water Treatment (RIZA), Lelystad, the Netherlands

© 2012: Nico Booij