open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi everyone,

I have run my case in telemac2d, which can be run successfully, however, when I check the water depth, I found it was unreasonable because most of the water depth is 5-10, however, the elevation of bottom is between 0.1-2, I don't know what my problem is.

the attached file is the water depth result, bottom, and the files of cas, geo file, cli file.

Any help will be appreciated!

yajuan

Hello,

Well the elevation is the elevation, and the depth is the depth, so I do not really catch where there is a problem. With a bottom at 0.1 m and a depth of 5 m the free surface elevation will be at 5.1 m, that's how it works, or am I missing something ?

Regards,

Jean-Michel Hervouet

Dear JMH,

Thank you very much for your quick reply! Allow me to explain:

For initial condition, we have chosen constant elevation and has input initial elevation as 10m. But, I realised that our domain is very large, as in the elevations vary by a big margin.

As mentioned in manual: "this technique cannot be used if the model domain is very large, as the initial elevation generally means that there will be a dry area upstream of the model".

Our results show exactly the same as quoted in the manual.

Actually, we intend to run steady simulation & at the river mouth, we want to control the water surface elevation to 0.4m (known mean sea elevation). How can we go about defining this function in the cas file?

Best regards!

yajuan

Hello,

OK, this is a common problem in long rivers, and a constant elevation is not a solution. here are 4 possibilities:

1) you put a constant depth everywhere and the water will flow down in its correct position during the first time steps (ugly, lots of supercritical flows, but it generally works).

2) BlueKenue and Fudaa allow you to give a not too unrealistic free surface elevation to start the computation.

3) Start from a dry river, except at the entrance, and fill it till reaching a steady state, use this as restart conditions for further computations (it may take time).

4) program yourself a tentative initial free surface in condin.f (see the section allowed for INITIAL CONDITION = 'SPECIAL')

With best regards,

Jean-Michel Hervouet

Dear JMH,

Thank you for your so kind suggestion!

I will try to do. If I have some question I will ask for your help. Thanks!

Best regards!
yajuan

Dear JMH,

Thank you for your help!

If I want to modify the subroutine "CONDIN.f", what should I modify at this section, I am sorry to ask you so detailed question. I have found the CONDIN.f and the corresponding code for users, the coding is as following,

! TO BE MODIFIED BY USER IF SPECIAL INITIAL CONDITIONS
!
IF(LNG.EQ.1) WRITE(LU,10)
IF(LNG.EQ.2) WRITE(LU,11)
10 FORMAT(1X,'CONDIN : AVEC DES CONDITIONS INITIALES PARTICULIERES'
& ,/,' VOUS DEVEZ MODIFIER CONDIN')
11 FORMAT(1X,'CONDIN : WITH SPECIAL INITIAL CONDITIONS'
& ,/,' YOU HAVE TO MODIFY CONDIN')
CALL PLANTE(1)
STOP
!
! END OF CODE TO BE MODIFIED BY USER

Thank you very much!

yajuan

Hello,

Here is an example (provided that INITIAL CONDITION='SPECIAL'), with a tentative linear free surface as a function of coordinate X : 0.1D0(X-450.D0)

INTEGER I
! TO BE MODIFIED BY USER IF SPECIAL INITIAL CONDITIONS
!
!IF(LNG.EQ.1) WRITE(LU,10)
!IF(LNG.EQ.2) WRITE(LU,11)
!10 FORMAT(1X,'CONDIN : AVEC DES CONDITIONS INITIALES PARTICULIERES'
!& ,/,' VOUS DEVEZ MODIFIER CONDIN')
!11 FORMAT(1X,'CONDIN : WITH SPECIAL INITIAL CONDITIONS'
!& ,/,' YOU HAVE TO MODIFY CONDIN')
!CALL PLANTE(1)
!STOP
!
DO I=1,H%DIM1
H%R(I)=MAX(0.1D0(X(I)-450.D0)-ZF%R(I),0.D0)
ENDDO
!
! END OF CODE TO BE MODIFIED BY USER

Good luck,

JMH

Dear JMH,

I have recompiled telemac2d according to your suggestion of the CONDIN.f successfully, and I can run my own case successfully, however, I found I cann't define the H%R(I) correctly to get more realistic waterdepth, can you give me some suggestion about the function?

Our river is a long river and the bottom elevation vary much, and the downstream is the mouth of the sea, normally, the water depth is 0.4m, then the water surface should the 0.4 add the bottom elevation(about 2m), that is 2.4m. but how can I define the function in CONDIN.f to match my case?

The attatched file is the bottom file and cas file. BTW, the geo file is too big that I can not upload, so the attached file is the BOTTOM screen capture with the legend.

Thank you very much in advance!

Best regards!
yajuan

Dear JMH,

The attached file is the BOTTOM screen capture with the legend, I am sorry that I forgot to upload the file just now.

Best regards!
yajuan

Hello,

You must not change subroutine condin.f in the library but take it in a FORTRAN FILE specific to your case and modify it there, otherwise all the other cases will work with your modified version.

Then it is difficult to answer the other question, you could define an approximate free surface elevation linear in x and y, with the correct elevation upstream and the correct elevation downstream. Even if it is very rough, it could be a good start and then you will have some intermediate unsteady flow before things settle in a more physical way.

Regards,

Jean-Michel Hervouet