open TELEMAC-MASCARET The mathematically superior suite of solvers

I'm rather new to modelling and have difficulty grasping some of the basic idea's.

In an earlier reply of Christophe to a post about: 'CONDIH Error even with Initial conditions = Zero Elevation', I read the following:

'Artemis is a frequency domain software, so there is no concept of number of waves, simulation time, etc... In regular waves, artemis provide an harmonic solution :
eta=amplitude * cos(kx - wt)
The free surface given as an output is the free surface for a given instant , says 0 for example.'

Can anyone explain me how the results are computed for the frequency domain software? And how ARTEMIS 'chooses' this given instant for the output. Is it possible to force an other instant?

I tried for instance, to compare some results of ARTEMIS with simple plots with matlab for the physical process of reflection (and with that the creation of a standing wave) by creating a very simplified rectangular mesh, constant depth with a fully reflecting wall. The result ARTEMIS gives for the free surface seems to be equal to my matlab calculation of adding the incident wave to the reflected wave at ¾ of a period. This would be, logically, the maximum result as the two waves are in phase at that moment. For a delayed reflection of the wall, ALFAP=60 degrees (and by hand calculation adding this phase to the reflected wave) I only got similar results by trial and error for a delay of 150 degrees and a time step of around 7 seconds in my MATLAB calculations. It is again a maximum though. Is it true that ARTEMIS automatically chooses the maximum result? If so, how does it do that and is it possible to see which instant is chosen? Can I get results for different moments in time? Or is my time thinking totally wrong?

(as this description of my example is probably not too clear, I added a word document showing what I did as well)

Thanks for the help!

Hi,

For the free surface, according to linear hypothesis, ARTEMIS output is eta=-omega/g * Imag(Phi) , with Phi the potential.
Phi is the quantity solved by ARTEMIS, so I guess if you change the incident wave phase, you should change the free surface output from ARTEMIS.

The free surface is only here for information, as only 1 instant is printed. I suggest you to plot the wave height to compare with your matlab file... or change the incident phase.

Christophe