This tutorial uses an example of a ball check valve to demonstrate two-way Fluid-Structure Interaction (FSI) between a ball and a fluid, as well as mesh deformation capabilities using ANSYS CFX. A sketch of the geometry, modeled in this tutorial as a 2-D slice (0.1 mm thick), is shown below:

ball check valve

Simplified Geometry Model for Ball Check Valve

Check valves are commonly used to enforce unidirectional flow of liquids and act as pressure-relieving devices. The check valve for this tutorial contains a ball connected to a spring with a stiffness constant of 300 N/m. The ball is made of steel with a density of 7800 kg/m³ and is represented as a cavity region in the mesh with a diameter of 4 mm. Initially the center of mass of the ball is located at the spring origin, and all forces that interact with the ball are assumed to pass through this point. The tank region, located below the valve housing, is filled with Methanol (CH4O) at 25°C. High pressure from the liquid at the tank opening (6 atm relative pressure) causes the ball to move up, thus allowing the fluid to escape through the valve to the atmosphere at an absolute pressure of 1 atm. The forces on the ball are: the force due to the spring (not shown in the figure) and the force due to fluid flow. Gravity is neglected here for simplicity. The spring pushes the ball downward to oppose the force of the pressure when the ball is raised above its initial position. The pressure variation causes the ball to oscillate along the Y-axis as a result of a dynamic imbalance in the forces. The ball eventually stops oscillating when the forces acting on it are in equilibrium.

In this tutorial the deformation of the ball itself is not modeled; mesh deformation is employed
to modify the mesh as the ball moves.


Video 1: Video Animation of Transient Mesh Deformation with Ball Check Valve 

A rigid body simulation is used to predict the motion of the ball, and will be based on the forces that act on it. For further details on rigid body capabilities within ANSYS CFX, refer to Rigid Bodies in the CFX-Pre User's Guide.


Video 2: Video Animation of Transient Flow Velocity through Ball Check Valve