increase of courant number ,even after using automatic control time step
 

Hello every one,

I am new to Open Foam and running a user made solver and it work well for 2d & 3d case of rectangular channel.But when i am running it for a wedge of annulus case where my inner cylinder is rotating with 1 rad/sec and it also has pressure driven flow from bottom with uniform velocity of 0.0063 m/s, and i generated my geometry in design modular. But my courant increased exponentially and finally core will be dumped. To solve this problem i used automatic control of courant number by set control header file,it work fine during initial iteration ,but after some iterations courant value increased exponentially and my core damping messgae appeared on my terminal.
please guys help me out of this.


Thanks in advance:)

Shadab Ilahi

Hi Shadab,

Can you tell you what is this user made solver based on?

A personal experience with complex cases is to find a working case (like your rectangular channel) and then start one step at a time from there rather than jumping to the final case. You might want to go with the wedge only first, and then add the pressure driven and finally rotation. So you can spot where the problem is rising from.

Thank u Mahdi for your response,
My solver is based on shear induced migration phenomenon and i already simulate the result with annulus cylinder for case of driven flow ,and then with rotation of inner cylinder with different rotation speed get the results.Later than i want to tried fine meshing in annulus wedge and fine meshing of whole Annulus cylinder and controlling my courant number by set control.h header file, even though the courant number increased after few iteration suddenly and my core will be dumped.
i am unable to understand the error which printing on screen ,Hoping that u would tell me the exact problem and solution. this is the error message


--> FOAM Warning :
From function Time::operator++()
in file db/Time/Time.C at line 1055
Increased the timePrecision from 7 to 8 to distinguish between timeNames at time 0.00712815
Time = 0.0071281531

Courant Number mean: 2.12511e+57 max: 4.45148e+60
deltaT = 4.90283e-100
#0 Foam::error::printStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::multiply(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::operator*<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<doub le, Foam::fvPatchField, Foam::volMesh> > const&, Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) at ??:?
#5
at ??:?
#6 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#7
at ??:?
Floating point exception (core dumped)




thanks in advance .