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Dear Users,

I am trying to run a case where I have two strong stratified layers in domain and a source discharge at the bottom of closed boundary. There are three closed boundaries and one open. No velocity in domain. The water discharge of source is 50m3/s, and velocity of discharge is x=2.0 and y=0.0. Two tracers Temp and Salinity. The run stops immediately with error message MURD3D: Iteration no reached 100, Stop. I have other similar cases who run for few days and they gave me the same error. I attached my output file, cas and fortran files. Please advise what I need to change. Thank you.

Kind Regards!

Violeta

Hello,

This number of iterations is about the CFL number as computed by the PSI scheme, it would mean that you have high advection velocities somewhere. Also think that advection schemes 3,4 and 5 divide by the volumes around points in their solution procedure, so they will not work with tidal flats OR with crushed elements (if you impose the elevation of a plane and this elevation goes below the bottom, it results in crushed elements, this can work, but not with all advection solvers). You can bypass the problem by provisionally choosing the method of characteristics for the advection schemes:

SCHEME FOR ADVECTION OF VELOCITIES =1
SCHEME FOR ADVECTION OF TRACERS =1
SCHEME FOR ADVECTION OF K-EPSILON =1

then hopefully you will have a result and will be able to see what happens and if there are some high velocities somewhere. When it works I would suggest the final combination:

SCHEME FOR ADVECTION OF VELOCITIES =1
SCHEME FOR ADVECTION OF TRACERS =5
SCHEME FOR ADVECTION OF K-EPSILON =1

If it is a problem of tidal flats or crushed element you would need to have:

SCHEME FOR ADVECTION OF VELOCITIES =14
SCHEME FOR ADVECTION OF TRACERS =14
SCHEME FOR ADVECTION OF K-EPSILON =14

With best regards,

Jean-Michel Hervouet

Thanks a mil Jean-Michel. I will follow your advice.

Kind Regards!

Violeta

Dear Jean-Michele,

Thanks again for your reply on my post. I have changed the SCHEMEs to the value 1 (I have tried 1;5;1 and 14;14;14 as well):


SCHEME FOR ADVECTION OF VELOCITIES =1
SCHEME FOR ADVECTION OF TRACERS =1
SCHEME FOR ADVECTION OF K-EPSILON =1

and I got slightly different error message this time, as GRACJG (BIEF) : EXCEEDING MAXIMUM ITERATIONS: 100 RELATIVE PRECISION: 0.1499761E-01
STOP 2

This time I do not have discharge, just a two stratified layers with two tracers: Temp and Salinity. It crashes just after 200 time steps (time step =1). I attach the output, steering and fortan files. Maybe there is something wrong with my geometry? Also parameters I used are similar to the Validation Case - Stratification, so I cannot understand why it is not working for my case. But more likely that I made a mistake assigning some parameters as I am still have to learn a lot in this field. Please advise. Thank you.

Kind Regards!

Violeta