Pinch Mode Magnetorheological Flow Bench: Fluid Flow Analysis

Abstract

Magnetorheological (MR) fluids are known smart materials. In the presence of magnetic field the material develops a yield stress. The technology has been used in the automotive industry, for example, or high quality optical finishing applications. In the (existing) conventional flow-mode valves the MR fluid is energized by magnetic flux perpendicular to the fluid flow path. The effect is an increase in the material's effective resistance-to-flow. The so-called gradient pinch mode (GPM) follows a different principle -the flux in the flow channel is directed to activate the fluid in the areas adjacent to the channel walls. Then, high yield stresses are induced in the material in the adjacent zones and low yield stresses are achieved in the middle of the channel, the yield stress distribution is non-uniform. As a result, a Venturi-like contraction is formed solely by material means, i.e. without changing the flow path geometry. This may lead to a new category of controlled semi-active valves. However, a fundamental research is still required to characterize the rheology of MR fluids in this mode. In the study the authors explore opportunities for building a pinch mode valve assembly for the experimental work with MR fluids. The authors propose a solenoid assembly that can be integrated into a flow bench, and then proceed with a CFD steady-state study of the fluid flow through the valve. The results are then presented in the form of velocity plots and pressure maps as well as averaged pressure drop vs volumetric flow rate, respectively, at various levels of ampere turns.