[mattms]

I am attempting to use the Laser DTRM feature with the icoReactingMultiphaseInterFoam solver. I am trying to model a moving laser. When the laser is stationary, heat is transferred as expected, but when it moves (as below), the barely any heat is transferred. Am I missing something, or is there a better radiation model to use?


radiationModel laserDTRM;

absorptionEmissionModel constantAbsorptionEmission;
mode "Gaussian";
nTheta 70;
nr 30;
focalLaserPosition table
(
(0 (0.000500 0.000150 0.000125))
(0.0002 (0.000750 0.000150 0.000125))
);
laserDirection constant (0 0 -1);
focalLaserRadius 0.000050;
laserPower 1200;
sigma 0.000049;

absorptivity absorptivity [0 -1 0 0 0 0 0] 0.8;
emissivity emissivity [0 -1 0 0 0 0 0] 0.4;
E E [1 -1 -3 0 0 0 0] 0;

[gentodin]

Originally Posted by mattms

I am attempting to use the Laser DTRM feature with the icoReactingMultiphaseInterFoam solver. I am trying to model a moving laser. When the laser is stationary, heat is transferred as expected, but when it moves (as below), the barely any heat is transferred. Am I missing something, or is there a better radiation model to use?


radiationModel laserDTRM;

absorptionEmissionModel constantAbsorptionEmission;
mode "Gaussian";
nTheta 70;
nr 30;
focalLaserPosition table
(
(0 (0.000500 0.000150 0.000125))
(0.0002 (0.000750 0.000150 0.000125))
);
laserDirection constant (0 0 -1);
focalLaserRadius 0.000050;
laserPower 1200;
sigma 0.000049;

absorptivity absorptivity [0 -1 0 0 0 0 0] 0.8;
emissivity emissivity [0 -1 0 0 0 0 0] 0.4;
E E [1 -1 -3 0 0 0 0] 0;

Hi, I too have the same issue at the start but apparently, it has something to do with solver frequency? Other than that another possible solution is that it is because of the unit of laser power. I cant be sure as I cant find any document let me know if you can!

This is mine incase you want to check.

radiation on;

radiationModel laserDTRM;


// Number of flow iterations per radiation iteration
solverFreq 5;

absorptionEmissionModel constantAbsorptionEmission;
mode "Gaussian";
nTheta 20;
nr 10;
opd 0.1;
//focalLaserPosition constant (0.025 0.05 0.05);
focalLaserPosition table
(
(0 (0.025 0.02 0.05))
(160 (0.025 0.2 0.05))
);
laserDirection constant (0 0 -1);
focalLaserRadius 0.005;
laserPower 50000;//mW?
sigma 0.005;

//qualityBeamLaser 1.0;

absorptivity absorptivity [0 -1 0 0 0 0 0] 0.8;
emissivity emissivity [0 -1 0 0 0 0 0] 0.4;
E E [1 -1 -3 0 0 0 0] 0;


scatterModel none;

sootModel none;

transmissivityModel none;

Im not sure if the laser power is of mW unit or W unit as I could only get higher temperature when I assume it is mW.

[openfoammaofnepo]

Hello,



In the table for focalLaserPosition, what does the first number and the vector mean?



Thank you very much!



focalLaserPosition table
(
(0 (0.025 0.02 0.05))
(160 (0.025 0.2 0.05))
);

Originally Posted by gentodin

Hi, I too have the same issue at the start but apparently, it has something to do with solver frequency? Other than that another possible solution is that it is because of the unit of laser power. I cant be sure as I cant find any document let me know if you can!

This is mine incase you want to check.

radiation on;

radiationModel laserDTRM;


// Number of flow iterations per radiation iteration
solverFreq 5;

absorptionEmissionModel constantAbsorptionEmission;
mode "Gaussian";
nTheta 20;
nr 10;
opd 0.1;
//focalLaserPosition constant (0.025 0.05 0.05);
focalLaserPosition table
(
(0 (0.025 0.02 0.05))
(160 (0.025 0.2 0.05))
 
laserDirection constant (0 0 -1);
focalLaserRadius 0.005;
laserPower 50000;//mW?
sigma 0.005;

//qualityBeamLaser 1.0;

absorptivity absorptivity [0 -1 0 0 0 0 0] 0.8;
emissivity emissivity [0 -1 0 0 0 0 0] 0.4;
E E [1 -1 -3 0 0 0 0] 0;


scatterModel none;

sootModel none;

transmissivityModel none;

Im not sure if the laser power is of mW unit or W unit as I could only get higher temperature when I assume it is mW.

[TeresaT]

Hi,

Originally Posted by openfoammaofnepo

Hello,

In the table for focalLaserPosition, what does the first number and the vector mean?


focalLaserPosition table
(
(0 (0.025 0.02 0.05))
(160 (0.025 0.2 0.05))
);

(Time (x y z)) This way you can determine where the direction and velocity of the laser.

@Gentodin and mattms

If not enough heat is transmitted during movement you may want to recalculate the laser velocity (movement made between two points in the table).

However, maybe there is enough heat transmitted but it is "consumed" by the phase above your solid? You might not see this at first but check the temperature field shortly after you started the laser.

If that is the problem use localDensityAbsorptionEmissionCoeffs,
e.g.:

localDensityAbsorptionEmissionCoeffs
{
alphaNames (alpha.gas alpha.liquid alpha.solid);
aCoeff (0 1e3 1e8);
eCoeff (0 0.35 0.35);
ECoeff (0 0 0);
}