We start with :
\frac{\partial (\rho \phi)}{\partial t} + \nabla \, ( \rho \, {\bf u}) = \rho \cdot \sum_k q_k(t) \cdot \delta({\bf r}-{\bf r}_k) |
See also
Physics / Mechanics / Continuum mechanics / Fluid Mechanics / Fluid Dynamics / Pressure Diffusion / Pressure Diffusion @model / Pseudo-linear pressure diffusion @model