CFD Online Discussion Forums - Strange behaviour - custom boundary condition runs many times in 1 timestep

Hi,

I tried to create a boundary incoming U boundary condition to change its value at each timestep. I tried using codedFixedValue and now also high lvl programming.

I tried to print some variables such as U, time for debugging purpose but I realised somethings strange - the U velocity is changed twice in 1 timestep when running simpleFoam. Moreover, if pimpleFoam is used, it runs even more -> twice within each pimpleFoam iteration.

My code is

Code:

inlet

    {

                type            codedFixedValue;

                value           $internalField;

                name    u_6dof_change;

                code

                #{

                

                        scalar cur_incoming_vel;

                        

                        

                        const fvPatch& boundaryPatch = patch(); 

                        vectorField& field = *this;

                

                        forAll(boundaryPatch, faceI) {

                                

                                field[faceI] =  field[faceI] + vector(1., 0,0);

           

                                cur_incoming_vel = field[faceI].component(vector::X);

                                

                        }

           

                        Info << "current incoming velocity = " << cur_incoming_vel << endl;

                   

                        

           #};

From simpleFoam

Code:

Starting time loop



Time = 0.0001



current incoming velocity = 2

smoothSolver:  Solving for Ux, Initial residual = 1, Final residual = 6.81739e-09, No Iterations 18

smoothSolver:  Solving for Uy, Initial residual = 1, Final residual = 7.71109e-09, No Iterations 16

GAMG:  Solving for p, Initial residual = 1, Final residual = 0.00713548, No Iterations 11

time step continuity errors : sum local = 2.62419e-08, global = -1.09807e-09, cumulative = -1.09807e-09

current incoming velocity = 3

current incoming velocity = 4

ExecutionTime = 0.14 s  ClockTime = 0 s



Time = 0.0002



smoothSolver:  Solving for Ux, Initial residual = 0.478384, Final residual = 3.57783e-09, No Iterations 18

smoothSolver:  Solving for Uy, Initial residual = 0.37882, Final residual = 9.38104e-09, No Iterations 16

GAMG:  Solving for p, Initial residual = 0.104267, Final residual = 0.0010176, No Iterations 10

time step continuity errors : sum local = 1.40033e-07, global = -2.25939e-08, cumulative = -2.3692e-08

current incoming velocity = 5

current incoming velocity = 6

ExecutionTime = 0.17 s  ClockTime = 0 s



Time = 0.0003

Why is this so? I only want it to run once per time step. How can I prevent this from happening?