open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi ,

I have been recently attempting to utilize the Drogues in an already validated Telemac 3D model for tracking water particles. I have studied the relevant instructions for the Drogues feature in the Telemac 3D user manual and made some modifications to the Fortran files based on the particles case in Telemac 3D.

During this process, I initially encountered a problem when my .cas file had the keywords GEOGRAPHIC SYSTEM = 1,
SPHERICAL COORDINATES = YES,
and SPATIAL PROJECTION TYPE = 3.

It was evident that the coordinate system of my Geometry file was in latitude and longitude. Therefore, instinctively, I initially wrote the X, Y, and Z coordinates in latitude and longitude format, corresponding to the ADD_PARTICLE function in the user_flot3d.f file. However, this behavior resulted in errors similar to "PARTICLE OUT OF THE DOMAIN" in the model's log.

Later, I found a related post on Telemac forum, which suggested that even if the Geometry file is read in latitude and longitude coordinates, they would be converted to Mercator projection during the Telemac equation solving process. Thus, when I wrote the X, Y, and Z coordinates in the user_flot3d.f file in the form of Mercator projection, the model ran smoothly.

However, a second issue arose as a result. Since the X, Y, and Z coordinates in the user_flot3d.f file were in Mercator projection form, the X coordinate was 13510346.D0, and the Y coordinate was 3907241.D0. When outputting the Drogues ASCII file, the X coordinate appeared as an asterisk (*). It is evident that the character length of the X coordinate exceeds 15. Therefore, I would like to ask if there is a solution or idea to this problem?

The attachments are the .cas file of the model, the user_flot3d.f file, and the Drogues output ASCII file.

Best regards, Oliver.

Hello Oliver,

I think nearly everything you have written is right.

Which release do you use? V8P3 or V8P4?
FYI GEOGRAPHIC SYSTEM keyword should be equal to 5 if using SPHERICAL COORDINATES = YES. If you look at the listing, at the beginning, there should be a message telling you:
GEOGRAPHIC SYSTEM AUTOMATICALLY SET TO 5
WHEN MODELLING TIDE WITH SPHERICAL COORDINATES

Indeed, the coordinates you give should be in the right geographic system when used by TELEMAC-3D. When SPHERICAL COORDINATES = YES, Mercator projection coordinates are expected when dealing with drogues when the computation is at that step.

Your issue is indeed because the format used to write ASCII DROGUES FILE is overflowed.
You can change it adding e.g. $HOMETEL/sources/utils/bief/utimp_drogues.f in Fortran file and changing format 301 at line 398 by, e.g.:

You can even change 7 by 6 or 5 I think. In meters, having distances less than 1 micrometer should be too much.

Hope this helps,

Chi-Tuan

Hi,Chi-Tuan

Thanks a lot for your reply.

I am currently using version V8P4. Indeed, there is such information at the beginning of the listing. I have overlooked these details before, and that was my mistake.

In addition, the solution you provided is very effective and has successfully resolved my issue.

Thanks again ，

Oliver