2.5 Fluid-Solid interaction

In the case of a fluid-solid interaction the solid experiences pressure forces by the fluid, which are given by

 

$$\vec{f} = -\vec{n}p = - \vec{n}\rho\dot{\psi}.$$ (10)

Furthermore, due to continuity requirements, the normal component of the particle velocity $\partial\psi/\partial n$ of the fluid must meet the normal component of the surface velocity v_n of the solid at the interface. Thus, the following coupling condition at the fluid-solid interface results

 

$$v_{\mathrm{n}}=\vec{n}\cdot\left(\frac{\partial\vec{d}}{\partial t}\right) = -\vec{n}\cdot\nabla\psi = -\frac{\partial\psi}{\partial n}.$$ (11)