Fluid-Structure Interaction: 2-damper (axis symmetric model)

Figure 1: Model

The damper consists of a tube in which two chambers are separated by a piston. The piston (structural model) is connected to a spring and moves along the tube wall with frictional contact. The fluid transport from chamber to  chamber is realized by an orifice in the piston.

Figure 2: Animation

The animation shows the velocity vectors in the fluid chamber, Mises-stresses in the piston and the contact forces on the piston. At the beginning of the simulation, the stretched spring forces the piston to move up. The piston oscillates in the tube by pushing the fluid from one chamber to the other. Due to wall friction and fluid viscosity the piston is damped. 

Figure 3: Time history  

Figure 3 shows the time history of the piston for various viscosities and wall-friction parameters. First, it is assumed that the viscosity (water) and the wall friction coefficient µ are very low so that the damping is also very low. In the second case, the viscosity is increased (machinery oil) so that the damping is higher. In the last case, the fluid viscosity again is low, but the wall friction coefficient is increased, which again results in a strong damping