Physics-based modeling of Magneto Rheological dampers

Magneto Rheological dampers are energy dissipating devices of various sizes that contain a particle-filled fluid that changes characteristics under the effect of a magnetic field. They are used in various applications such as automotive components, human joint replacements, and seismic protection in large structures. Current mathematical models of these devices are mostly based on phenomenological representations. These models have been found to not adequately explain certain behaviors observed in laboratory testing, especially in large MR dampers used in seismic applications. In an attempt to better understand particular behaviors of these devices, in this work detailed models of a damper are developed. The approach used for modeling is physics-based, considering the geometry and fluid characteristics of the damper assembly. Two such models are presented. The first is a simple, one dimensional model based on the Navier-Stokes equations, and is motivated by previous research using a physics-based approach. It employs a Bingham representation for the MR fluid. The second model is two dimensional and is intended to better capture the pressure build-up on either side of the damper piston. A two dimensional Navier-Stokes solver was developed based on the well-known SIMPLE algorithm of Patankar. In this work, the piston is kept fixed and the simulation is driven by setting the inlet and outlet flows. The effect of the magnetic field is simulated by varying the rheological properties of the fluid. The strength of the one dimensional model is in showing the yield patterns of the MR fluid between the piston and damper wall. The strength of the two dimensional model is that it shows the fluid patterns over the entire damper for varying magnetic fields. The results of the two methods are explored and compared in order to analyze the MR damper under the affect of a varying magnetic field. Close examination of the results from both models can give a better understanding of the damper behavior. This work lays the foundation for subsequent research on detailed models of MR devices.