i have a question on the interpolation of the flow velocity at the particle position. This is what the CFX theory says: "In the calculation of all the forces, many fluid variables, such as density, viscosity and velocity are needed at the position of the particle. These variables are always obtained accurately by calculating the element in which the particle is traveling, calculating the computational position within the element, and using the underlying shape functions of the discretization algorithm to interpolate from the vertices to the particle position" I think this works if the particle size is smaller than the cell size and does not work if it is bigger. Or am I wrong?

Hi,

Yes, for Lagrangian particle tracking it is assumed the particle is small compared to the grid size. If the particle is larger than the mesh size then you should look at the immersed body model coming in CFX V12.

Glenn Horrocks