open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi everybody,

I just want to ask if anybody could tell me the difference between the subroutine: coefro.f and friction_calc.f, in terms of calculating the friction coefficient? Which one is used in TELEMAC2D?

Furthermore in the subroutine friction_calc.f, if I choose the Manning's law, this equation will be triggered:

CASE(4)
!
DO I = N_START, N_END
CF%R(I) = 2.D0*GRAV*(CHESTR%R(I)**2)/HC%R(I)**TIERS
ENDDO

As I can see, the friction coefficient CF is already dependent on the depth at time i. Does this make sense to modify the code to implement an extra dependency of the Manning CHESTR on the depth, just before the equation?

Finally what does the %R mean (in HC%R)?

I have searched all the forum but found no answers.
Thank you for your help!

I mistook the character I. It ist the number of node and not the time.
Also %R is the component storing the real data of vectors.

So my questions are: which water depth HC is used for calculating the friction coefficient? (in the source code it is MAX(H, HMIN), but what are they?)

And how is the best way to implement the relationship between friction coefficient and depth for each time step DT?

Hello Anna,

Sorry for the delay to answer.

Which release do you use?
Do you use Finite Elements of Finite Volumes?

Until release v8p1, COEFRO is used with Finite Volume whereas FRICTION_CALC is used with Finite elements.
From v8p2r0, COEFRO is not used in 2D anymore, only in 3D.

HMIN = 1.D-4 m (see which subroutine calls FRICTION_CALC: FRICTION_UNIF and FRICTION_ZONES).
H is water depth at new time step.

I usually use the laws of bottom friction already available in TELEMAC-2D (Strickler, Nikuradse or Chezy) and never tried to implement another one as they are OK for what I model.

Hope this helps,

Chi-Tuan