open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi Chi Tuan,

Thank you very very much for your help and the attached documents.It doesn't matter that one is in French;I'm a french speaker
I'll apply all your advises and recompare the ADCP data and the calculated one;hope it'll fit this time.(As I have seen yours working really well. )

Regards

Hanna

PS.:I would have liked to go to the workshop,but I'm just doing an internship.

Hi all,

In order to save some space, I have removed the report about modelling tides with version 6.1 of TELEMAC-2D as it has been available in Home section, then Training and tutorials section. Its name is "Méthodologie pour la simulation de la marée en Manche et proche Atlantique".

Regards,

Chi-Tuan

Hi Hannah,

Have you succeeded in getting better results with your simulations?

I attach one quick tentative of two subroutines to solve some problems you may have: the TPXO module with the possibility to change the reference of your bathymetry from CD to MSL (subroutine CD2MSL, with the last argument to calibrate the sea level if needed) and also a correction if you do not change your reference for bathymetry (e.g. CD) to start from correct elevations with 'ALTIMETRIE SATELLITE TPXO' option, but also one example of calling of CD2MSL subroutine in CORFON subroutine.

This TPXO module is only a temporary version just to help you with TELEMAC-2D and will be different for next version for sure (the argument MSL in CONDI_TPXO will have to be an argument of the subroutine, not an argument coming from a USE declaration).

Hope this helps,

Chi-Tuan

Hi Chi-Tuan,

thank you for the subroutine and your additional help.
I tried a simulation with the bathymetry file where I changed the reference to mean sea level with BK by an addition of the average value.I know it's not a good solution because it's not dynamic.
The results were just a little better but not really.The disparity between the components U and V still exist as before.Particularly the amplitude of U is about 2 times smaler than the real data.V is quite OK.
I'll try a simulation with your subroutine.Hope that the results will be better.
Thank you a lot!
Regards,

Hanna

Hi Hannah,

What about the first two items ('COEFFICIENT DE CORIOLIS' = 1.11E-4) and 'LOI DE FROTTEMENT' not equal to 0? Are there no improvements when changing them? In my opinion, they may have more consequences on the results than changing the reference for bathymetry or calibrating the model with the coefficients for tides.

As your domain does not look too large, have you tried to compare U and V velocities time series at one boundary node (you prescribe the time series on open boundary) just to check if you have patterns like ADCP results or modelled results?

Can you tell me what resolution you have for bathymetry data, before interpolating it on your mesh? Moreover, could you remind me of the size of the elements if your mesh is different from the one you have already sent. If you have a chaotic area but not enough data for bathymetry, you can miss local variations and if the ADCP is located in such an area...

At last, how long were your ADCP results? Were there a lot of waves during the measurements (in particular from West or East)? If there were carried out in June 2009, it seems that during one week from 20th, except the night between 24th and 25th, significant waves were always lower than 1.5 m in the Alderney Race, which is not so big (source PREVIMER).

Regards,

Chi-Tuan

PS: I know that the tentative subroutine for TPXO module is not optimized but I will do the job for next version. It is just to help you quickly.

Hi Chi-Tuan,

I've taken a COEFFICIEN DE CORIOLIS = 1,10E-4 into acount.I calculated it with the formula which is given by the TELEMAC manual.I also took a LOI DE FROTTEMENT =3 with a coefficient=27 (as yours) into account.I equally followed all your advises and changed my case file.(This changed a little the results,nevertheless the amplitude of U is still two times smaller than ADCP while V is quite ok.)

The ADCP data begins on 19.06.09 and ends on 26.07.09.I checked with the meteorological data of SHOM, PREVIMER and METEO France. During the periode we are testing there were no prevailing winds nor significants waves.The waves were less than 1.5m high as you stated. Additionally I ran one case file with wind and atmospheric pressure.The wind blowing only on the W-E axis.It increased a little the amplitude of U but not that much.(différence about 1.5 comparing to 2 from before)

I dind't try to print out the data on a boundary node. But I checked that there are incoherences.

The bathymetry data is 1 point every meter on a regulary grid. After interpolation we have 1 point every 100m and in the zone where the two seabed peaks are, I have 1 point every meter. Otherwise in this region there is no other relief.

regards,
Hanna

Hi Hanna (I realised that sometimes, I did not write your first name correctly, sorry),

Your case is strange. I think that if you look at time series of horizontal components of velocity, you should get the same results as for the ADCP locations in your model. If you have not changed your geometry file since your first post, the extent of your area is something like 2.4 km x 4.0 km. The resolution of the European Shelf Solution is 1/30 degree (around 3.5 km) so that for your model, you only use a few nodes of ES tidal solution to interpolate the harmonic constants and the boundary conditions of your simulations are maybe too stressed by these interpolations.

As already told in a previous post, I am not used to modelling tides over so small areas and I would suggest you to enlarge the extent of your model, say 24 km x 40 km, at least (bigger should be better) and to include the shoreline in your model. I am not convinced that propagating tide over a "small" area gives good results. In order to compare your TELEMAC-2D model with ADCP measurements, I would extent your boundaries at least a few kilometers far from your ADCP locations (say at least 10 km, perhaps more, 20 km should be enough) so that your results are not too influenced by the boundary conditions.

I hope this will help,

Chi-Tuan

Hi Chi-Tuan,

Never mind my first name;the way you wrote it is more common.

Actually,I'm trying to enlarge the zone to a size of round about 14 x 16km, which thus includes some coastal shorelines.(part of Alderney and part of the French continent,next to Cherbourgh)

When I succeed I'll launch a simulation with this geometric file and hopefully it'll help.

Thank you a lot for your quick advises.

Regards,

Hanna

Hi again,

If I were you and if possible for you, I would include the whole Alderney island in the domain to model and would increase your choice of dimensions twice or thrice, but excluding Guernsey, Sark or Cherbourg harbour.

Anyway, you can try your choice + my last advice and tell me which one gives better results, I would be interested in.

Hope this helps,

Chi-Tuan

Hi Chi-Tuan,

here are the results with the larger zone (my choice;14km x 25km).Alderney is completly included and on the other side you have the franch mainland of Cherbourgh.
The results are a little better, but I have still the problem on the velocity component U, but the difference in amplitude is getting smaller.
The point ADCP T_61 is next to the two seabed peaks and T_75 is in the S-E of my former zone.
The red line stands for the ADCP data. The blue one represents the simulation data with the enlarged zone and the green one is the simulation with the former zone.

I'll try an even bigger zone right now which will be 36km x 41km.

Regards,

Hanna