[tjt]

Hi,

I am a bit stuck with some SPH code and hope somebody out there can help...

I have generated a geometry consisting of two spherical volumes formed of SPH particles. The spheres are different diameters and I am trying to calculate the curvature of the surface. I know that the curvature should be 1/radius but am not getting this result from my SPH code. I am getting the same curvature for each sphere so am trying to work out what I have messed up:-(

I am using the paper by Kelager as a guide - M. Kelager. Lagrangian fluid dynamics using smoothed particle hydrodynamics. Master’s thesis, University of Copenhagen, Department of Computer Science, 2006.

image.diku.dk/projects/media/kelager.06.pdf

The curvature, k, is defined as the Laplacian of the color field divided by the norm of the gradient of the color field. (Eqn 4.29)

For the gradient, I am looping through all neighbour cells and summing

mass(j)/density(j) * grad_W * dx/|r| for the X dir gradient
mass(j)/density(j) * grad_W * dy/|r| for the Y dir gradient
mass(j)/density(j) * grad_W * dz/|r| for the Z dir gradient

This looks like it gives the correct answer

For the Laplacian of the color field I loop through neighbours and sum

mass(j)/density(j) * laplacian_W

Do I need to multiply this by something - if so what. It isn't defined in the paper...

I am using poly 6 kernel and have coded gradient and Laplacian functions as per the paper.


Any advice would be very gratefully received