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Hi, all,

I am curious to couple particle tracing for fluid flow and matlab function.

I am testing the simple model. My geometry of the model is 1m along x-direction by 1m along y-direction. In the geometry, I release 121 particles. There are 11 particles along x-axis with 0.1 intervals from 0 to 1 and 11 particles along y-axis with 0.1 intervals from 0 to 1. So, there are 121 particles in the square (1m by 1m) geometry.

After releasing the 121 particles, I am trying to count the 121 particles using Matlab function. In this process, I need to transfer particle position components (qx and qy in Comsol) from Comsol to Matlab. I use the below Matlab code.

function test_function = test_function(qx,qy)

[p,q] = size(qx);
n = p * q ;

X = reshape(X, n,1);
Y = reshape(Y, n,1);

test_function = ones(n,1) .* n;

end

The expected value is 121. But the result in Comsol using above Matlab code is 11.

I hope you can tell me why this result, that is 11, came out. If you can not tell me it, would you tell me alternative method to count the particles. I attach the simple model.

Thank you in advance.

Changyeol