open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

I'm quite new to Telemac and have created a 2D tidal flow case using version v7p2. I've based the case on the 2D tidal tutorial example (the tutorial case runs fine) using TPXO for my tidal boundary and also have a river discharge in the system as shown in the attached figure.

My problem is that I am getting a net zero flow at the tidal boundary (see below) and wonder if anyone could help me understand why. I've also attached my .cas and .cli files.

Thanks,

Tom

================================================================================
ITERATION 270 TIME: 4 H 30 MIN 0.0000 S ( 16200.0000 S)

---

ADVECTION STEP

---

DIFFUSION-PROPAGATION STEP
GRACJG (BIEF) : 18 ITERATIONS, RELATIVE PRECISION: 0.9680391E-04
POSITIVE DEPTHS OBTAINED IN 7 ITERATIONS

---

BALANCE OF WATER VOLUME
VOLUME IN THE DOMAIN : 0.2458133E+12 M3
FLUX BOUNDARY 1: -16.94167 M3/S ( >0 : ENTERING <0 : EXITING )
FLUX BOUNDARY 2: -0.000000 M3/S ( >0 : ENTERING <0 : EXITING )
RELATIVE ERROR IN VOLUME AT T = 0.1620E+05 S : 0.2429226E-14

================================================================================
ITERATION 285 TIME: 4 H 45 MIN 0.0000 S ( 17100.0000 S)

---

ADVECTION STEP

---

DIFFUSION-PROPAGATION STEP
GRACJG (BIEF) : 18 ITERATIONS, RELATIVE PRECISION: 0.9674081E-04
POSITIVE DEPTHS OBTAINED IN 6 ITERATIONS

---

BALANCE OF WATER VOLUME
VOLUME IN THE DOMAIN : 0.2458132E+12 M3
FLUX BOUNDARY 1: -170.9340 M3/S ( >0 : ENTERING <0 : EXITING )
FLUX BOUNDARY 2: -0.000000 M3/S ( >0 : ENTERING <0 : EXITING )
RELATIVE ERROR IN VOLUME AT T = 0.1710E+05 S : -0.1172852E-14

///////////////////////////////////////////////////////

Hi,

It looks to me you have inflow at boundary 1 which is variable (negative at the last time steps), which is your tidal boundary.

You have net 0 flow at boundary 2, the river inlet. Change in cas file or provide liquid boundary file.

Regards,

Patrick

Thanks for your reply.

I was under the impression that the boundary numbers were sequential so the first was the river then the second was the tidal outlet:

#

---

# Defined Boundary Segments
:BoundarySegmentCount 2
#
# id code sectionCount startNode1 endNode1 startNode2 endNode2 tracerCode name
#
:BoundarySegment 1 455 1 1140 1143 1 1 2 "clyde_inlet"
:BoundarySegment 2 566 2 3384 3498 1 189 2 "outlet_sea"

Also, the river flow rate is a constant value as provided in the steering file:

PRESCRIBED FLOWRATES =100;0

VELOCITY PROFILES =1;1

Are these settings correct?

Regards,

Tom

Hello Tom,

Patrick is right, for TELEMAC-2D, your first open boundary is the maritime boundary. Please read subsections 3.2.3 and 4.2.3 of the TELEMAC-2D user manual for the boundary conditions file:

In the boundary conditions file you provide + the figure you sent, you can see that the 1st open boundary is the sea, not the river.

As suggested in another recent topic, you can run a script which plots the mesh + liquid boundaries and their number for TELEMAC-2D which may help you:
plot.py mesh2d name_geometry_file.slf -b name_BC_file.cli --liq-bnd

Which mesh generator do you use? Blue Kenue? I do not how it works and cannot use it, but for sure, what is important is what is generated as input for TELEMAC-2D: the geometry and boundary conditions file.

To answer your question about the 2 keywords and what you really want to do, you will find the answers in the TELEMAC-2D user manual:
- in $HOMETEL/documentation/telemac2d/validation and $HOMETEL/documentation/telemac2d/user with the 2 pdf files (if you use a tagged version, otherwise compile the documentations),
- or on wiki.opentelemac.org/doku.php?id=documentation_v8p1r1

For the T2D user manual, please read the latest one available in v8p1r1, it was updated a few months ago.

Hope this helps,

Chi-Tuan

Hi Chi-Tuan,

Thanks for these helpful and constructive comments.

I anticipate a few ups and downs in my new Telemac adventure!

Regards,

Tom

Yes, using Blue Kenue.