This tutorial involves a moving mesh and a two-way fluid-structure interaction (FSI) between a ball and a fluid in a check valve. The geometry, modeled as a 2-D slice (0.1 mm thick), is displayed below.

Check valves are commonly used to allow uni-directional flow. The check-valve in this tutorial is located on the top of a tank, and acts as a pressure-relieving valve by moving to allow fluid to leave. The ball is connected to a spring that acts to push the ball downward when the ball is raised above the y=0 position. The forces on the ball are the force due to the spring and the force due to fluid flow. Gravity is neglected here for simplicity. The ball is represented as a cavity region in the mesh. The deformation of the ball is not modeled.

The tutorial is divided into two parts. In the first part, the motion of the ball is controlled by CEL expressions which account for the forces acting on the ball, including the force imparted by the flow. In the second part of the tutorial, the motion of the ball is controlled by a Junction Box Routine that updates the ball position at the start of each timestep by loading mesh coordinate files from a set of such files. The mesh coordinate files and required Fortran routines are provided with this tutorial.