[ce73stargazer]

Hi Niels

I am trying to modify the waveFlume case with irregular waves, but I've been facing the issues of

--> FOAM Warning :
From function setWaveField::setWaveField( const fvMesh& mesh, volVectorField& U, volScalarField& alpha, volScalarField& p)
in file preProcessing/setWaveField/setWaveField.C at line 77

The specified value of Tsoft is non-zero in the waveType: `irregular'
specified in the sub-dictionary waveProperties :: outletCoeffs

Consequently, the initialised `wave field' is set to a horizontal free surface with zero velocity.

When i try to setWaveField. I am not sure what this means. Any suggestion?

[ngj]

Hallo Zhifang,

There is no problem, since it is merely a warning. You simply get still water as the initial field.

Kind regards,

Niels

[ce73stargazer]

Hi Niels
I tired applying irregular waves in the wave flume cases and it works fine.
However after i try to modify the geometry by putting a circular pipe on the bed and ran it again, it showed some really weird behavior. I found that the dT is keeping on shrinking and once it gets to a really small number the simulation stopped.
It showed like

Courant Number mean: 1.21062e-06 max: 0.522317
Interface Courant Number mean: 2.73909e-15 max: 5.03345e-11
deltaT = 2.71841e-105
--> FOAM Warning :
From function Time:perator++()
in file db/Time/Time.C at line 1061
Increased the timePrecision from 333 to 334 to distinguish between timeNames at time 0.0213757
Time = 0.021375665633658686576312746296935074497014284133 9111328125

PIMPLE: iteration 1
smoothSolver: Solving for alpha.water, Initial residual = 7.10539e-10, Final residual = 7.10539e-10, No Iterations 0
Phase-1 volume fraction = 0.499565 Min(alpha.water) = 0 Max(alpha.water) = 1
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.499565 Min(alpha.water) = 0 Max(alpha.water) = 1
Relaxing time: 1.34 s
DILUPBiCG: Solving for Ux, Initial residual = 0.0181335, Final residual = 2.02339e-12, No Iterations 3
DILUPBiCG: Solving for Uy, Initial residual = 0.0888651, Final residual = 8.79067e-13, No Iterations 3
GAMG: Solving for p_rgh, Initial residual = 0.00173562, Final residual = 5.73484e-08, No Iterations 11
GAMG: Solving for p_rgh, Initial residual = 0.00215153, Final residual = 6.9998e-08, No Iterations 9
time step continuity errors : sum local = 4.29896e-12, global = 8.99035e-13, cumulative = -7.13986e-10
GAMG: Solving for p_rgh, Initial residual = 0.00241302, Final residual = 7.70839e-08, No Iterations 11
GAMG: Solving for p_rgh, Initial residual = 0.0013268, Final residual = 8.11829e-08, No Iterations 9
time step continuity errors : sum local = 1.28082e-11, global = -2.74826e-12, cumulative = -7.16734e-10
GAMG: Solving for p_rgh, Initial residual = 0.00156527, Final residual = 7.11062e-08, No Iterations 10
GAMG: Solving for p_rgh, Initial residual = 0.00135456, Final residual = 8.03705e-09, No Iterations 12
time step continuity errors : sum local = 1.89521e-12, global = -4.68762e-13, cumulative = -7.17203e-10
ExecutionTime = 4210.68 s ClockTime = 4210 s

Courant Number mean: 1.21062e-06 max: 0.522317
Interface Courant Number mean: 2.73906e-15 max: 5.03345e-11
deltaT = 1.30113e-105
--> FOAM Warning :
From function Time:perator++()
in file db/Time/Time.C at line 1061
Increased the timePrecision from 334 to 335 to distinguish between timeNames at time 0.0213757
Time = 0.021375665633658686576312746296935074497014284133 9111328125

PIMPLE: iteration 1
smoothSolver: Solving for alpha.water, Initial residual = 7.10539e-10, Final residual = 7.10539e-10, No Iterations 0
Phase-1 volume fraction = 0.499565 Min(alpha.water) = 0 Max(alpha.water) = 1
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.499565 Min(alpha.water) = 0 Max(alpha.water) = 1
Relaxing time: 1.35 s
#0 Foam::error:rintStack(Foam::Ostream&) at ??:?
#1 Foam::sigFpe::sigHandler(int) at ??:?
#2 ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3 double Foam::sumProd<double>(Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#5 ? at ??:?
#6 ? at ??:?
#7 ? at ??:?
#8 ? at ??:?
#9 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#10 ? at ??:?
Floating point exception (core dumped)


I am not sure why dT will keep on shrinking, as my initial dT is 0.001s. Any suggestion?

[ngj]

Good morning

@Zhifang: If the case without the cylinder works, then there is obviously something wrong with the cylinder case, i.e. it is unlikely to be a waves2Foam related issues.
It is likely to be the mesh quality. The decreasing dt is a clear sign that your case is crashing.

Kind regards,

Niels

[ce73stargazer]

Thanks for the reply Niels. May I ask two general question related to Wave2Foam.

1.
For the irregular wave set-up, there is one parameter Hs, I am not sure this Hs is the significant wave height or the root mean squared wave height.

2.
Is it possible to extract the time series of the wave generated in Wave2Foam. I found that there are discrete individual wave amplitudes and phases information in waveProperties file, but is there a way to read the original time signal of the generated irregular wave?

[ngj]

Good morning Zhifang,

You are welcome.

Ad. 1: It is strictly speaking the spectral wave height, if one reserves the term significant wave height to the time domain analysis. In practice, these two wave heights are close to identical.

Ad. 2: True, there is no way for (easy) generation of the target surface elevation. I have it on my To-Do list already, but a time estimate for its release is uncertain.

Kind regards,

Niels

[ce73stargazer]

Hi Niels

Just some quick thoughts of recreating the real time signal. I did a few tests with setWaveParameters, I found that all the amplitude and frequency stay the same if the number of frequencies selected doesnt change, while the random phase changes. I am thinking of recreating the real signal by summing up those individual cos curves with the related phases just like the discrete Fourier series and i think that should be the real signal simulated.
Am I in the right track?

[ngj]

Good morning,

@Zhifang: It sounds like a reasonable approach to recreate a certain signal.

Kind regards,

Niels