[VnV][telemac3d] Update bendrans example with better choices for a few keywords

- TREATMENT OF NEGATIVE DEPTHS = 2 (new default value since release 9.0) and
TIDAL FLATS = YES (default value) to improve mass conservation of water
- use of gradient conjugate + preconditioning 34 = 2*17 to solve PPE, more
efficient than GMRES for this example (very few iterations are needed)
- ACCURACY FOR PROPAGATION = 1.E-15 as easily solved (only 2 iterations needed)
- ACCURACY FOR PPE = 1.E-9 (less than 10 iterations needed)
- PRECONDITIONING FOR DIFFUSION OF K-EPSILON = 34 to improve efficiency
(turbulent variable)
- PRECONDITIONING FOR DIFFUSION OF VELOCITIES set to default
(not understood why 0 previously, no clear differences)

examples/telemac3d/bendrans/doc/bendrans.tex

@@ -45,16 +45,34 @@ is made of 6,845 triangular elements (3,623 nodes).
 \end{figure}
 
 The time step is 0.01~s for a simulated period of 100~s.
+\\
 
 The non-hydrostatic version is used.
 To solve the advection, the characteristics
 are used for both velocities and turbulent variable (scheme 1).
+
 GMRES is used for solving the propagation and diffusion of velocities (option 7).
-Accuracies for every solving of linear system are set to the default value 10$^{-8}$
-except for the turbulent variable for which it is set to 10$^{-10}$.
-No preconditioning for the diffusion for velocities step is used.
+Accuracies are set to different values for every solving of linear system:
+\begin{itemize}
+\item 10$^{-8}$ for the diffusion of velocities (default value),
+\item 10$^{-15}$ for propagation (only 2 iterations are needed),
+\item 10$^{-9}$ for PPE (less than 10 iterations are needed),
+\item 10$^{-10}$ for the diffusion of the turbulent variable
+(keyword \telkey{ACCURACY FOR DIFFUSION OF K-EPSILON}).
+\end{itemize}
+%No preconditioning for the diffusion for velocities step is used.
+%No clear and significant differences with default = diagonal = 2)
+Preconditioning = 34 (= 2 $\times$ 17) is used for the diffusion of the
+turbulent variable to accelerate the solving
+(keyword \telkey{PRECONDITIONING FOR DIFFUSION OF K-EPSILON}).
+
 The implicitation coefficients for depth and diffusion are both equal to 0.51
 to be the more accurate.
+\\
+
+Mass conservation is improved (up to machine precision) by using default value
+for the keyword \telkey{TREATMENT OF NEGATIVE DEPTHS} (= 2), instead of the old
+default value = 1 (smoothings) for this example (until release 9.0).
 
 \subsection{Physical parameters}
 
@@ -74,6 +92,7 @@ the computation.
   \label{t3d:bendrans:FreeSurf}
 \end{figure}
 
+\newpage
 Figure \ref{t3d:bendrans:Velo} shows the magnitude of velocity at the end of the
 computation.
 The flow accelerates when turning in the bend and a detachment appears

examples/telemac3d/bendrans/t3d_bendrans.cas

@@ -5,7 +5,6 @@ GEOMETRY FILE            : geo_bendrans.slf
 LIQUID BOUNDARIES FILE   : t3d_bendrans.qsl
 3D RESULT FILE           : r3d_bendrans.slf
 
-TIDAL FLATS = NO
 NUMBER OF HORIZONTAL LEVELS = 5
 MESH TRANSFORMATION = 1
 NON-HYDROSTATIC VERSION = YES
@@ -24,19 +23,16 @@ COEFFICIENT FOR HORIZONTAL DIFFUSION OF VELOCITIES = 1.E-6  / DEFAULT
 COEFFICIENT FOR VERTICAL DIFFUSION OF VELOCITIES   = 1.E-6  / DEFAULT
 HORIZONTAL TURBULENCE MODEL = 5
 VERTICAL TURBULENCE MODEL   = 5
-PRECONDITIONING FOR DIFFUSION OF VELOCITIES = 0
+/PRECONDITIONING FOR DIFFUSION OF VELOCITIES = 0 / HARD TO SAY WHY 0 PREVIOUSLY
 
 SCHEME FOR ADVECTION OF VELOCITIES = 1
 SCHEME FOR ADVECTION OF K-EPSILON  = 1
 
-MAXIMUM NUMBER OF ITERATIONS FOR PPE = 400
-MAXIMUM NUMBER OF ITERATIONS FOR PROPAGATION = 800
-MAXIMUM NUMBER OF ITERATIONS FOR DIFFUSION OF VELOCITIES = 800
-MAXIMUM NUMBER OF ITERATIONS FOR DIFFUSION OF K-EPSILON = 800
-ACCURACY FOR PPE = 1.E-8
+ACCURACY FOR PPE = 1.E-9          / LESS THAN 10 ITERATIONS NEEDED
 ACCURACY FOR DIFFUSION OF VELOCITIES = 1.E-8
-ACCURACY FOR PROPAGATION = 1.E-8
+ACCURACY FOR PROPAGATION = 1.E-15 / ONLY 2 ITERATIONS NEEDED
 ACCURACY FOR DIFFUSION OF K-EPSILON = 1.E-10
+PRECONDITIONING FOR DIFFUSION OF K-EPSILON = 34
 FREE SURFACE GRADIENT COMPATIBILITY = 0.75
 
 INITIAL CONDITIONS : 'CONSTANT ELEVATION'
@@ -51,11 +47,3 @@ SOLVER FOR PROPAGATION = 7
 SOLVER FOR DIFFUSION OF VELOCITIES = 7
 
 MASS-BALANCE : YES
-/
-/ DEFAULT VALUES UNTIL V8P0 KEPT FOR NON REGRESSION
-IMPLICITATION FOR VELOCITIES = 1.
-OPTION OF SOLVER FOR PROPAGATION = 3
-OPTION OF SOLVER FOR DIFFUSION OF VELOCITIES = 3
-/
-/ DEFAULT VALUE UNTIL V8P5 KEPT FOR NON REGRESSION
-TREATMENT OF NEGATIVE DEPTHS = 1

examples/telemac3d/bendrans/vnv_bendrans.py

@@ -54,12 +54,12 @@ class VnvStudy(AbstractVnvStudy):
         # Comparison with the last time frame of the reference file.
         self.check_epsilons('vnv_2:T3DRES',
                             'f3d_bendrans.slf',
-                            eps=[1.E-6, 1.E-3, 1.E-4, 1.E-4, 1.E-5, 1.E-4, 1.E-5, 1.E-7])
+                            eps=[1.E-5, 1.E-4, 2.E-4, 1.E-5, 1.E-7, 1.E-6, 1.E-5, 1.E-15])
 
         # Comparison between sequential and parallel run.
         self.check_epsilons('vnv_1:T3DRES',
                             'vnv_2:T3DRES',
-                            eps=[1.E-6, 1.E-3, 1.E-4, 1.E-4, 1.E-5, 1.E-4, 1.E-5, 1.E-7])
+                            eps=[1.E-5, 1.E-4, 2.E-4, 1.E-5, 1.E-7, 1.E-6, 1.E-5, 1.E-15])
 
 
     def _post(self):