Time-Dependent Computational Fluid Dynamics and Quasi-static Analysis of Smart Dampers

UoM administered thesis: Phd

  • Authors:
  • Wael Abdelmoneam Elsaady

Abstract

Magnetorheological (MR) fluids are smart materials whose application is continuously growing in several MR fluid devices due to their remotely controllable characteristics which are the key factor of their smartness. MR fluids manifest highly nonlinear and multi-physics flow characteristics that involve non-Newtonian, viscoplastic and viscoelastic characteristics that are affected by the applied magnetic field. Modelling of these phenomena can be quite complicated. That is why most models developed for MR dampers, which are the most common MR fluid devices, are not based directly on modelling of the rheological behaviour of the fluid. However, modelling of the rheological behaviour of MR fluids is considered to be necessary, as it provides more understanding of the flow parameters that cause the nonlinear behaviour of MR fluids and MR fluid devices. In response to that requirement, this thesis presents analytical, numerical and experimental approaches to model the performance of MR dampers and study the characteristics of rheological fluid flow in the damper. In addition, a novel MR damper with enhanced magnetic characteristics has been designed, manufactured, modelled and tested. The effects of applying these enhanced characteristics in the novel design have been evaluated based on the analytical and numerical models. The numerical method presented in the current thesis is considered to be useful not only to model the performance of MR dampers, but also for other MR fluid applications in which the rheological characteristics of fluid flow are necessary to be modelled. Using an analytical model, the performance of an MR damper has been determined based on modelling the flow parameters that are affected by fluid compressibility. Furthermore, a novel coupled numerical technique developed using the utilities of Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) has been established. The model couples the solution of the magnetic circuit, implemented by COMSOL/Multiphysics FE solver, with the solution of the fluid flow that is investigated by ANSYS/Fluent CFD solver. The coupled numerical approach accounts for more phenomena, more parameters of design, and involves fewer assumptions compared to analytical models. The theories, characteristics and limitations of both analytical and numerical methods are discussed. The numerical approach has been found to be capable of predicting the experimentally measured performances of MR dampers. Moreover, it predicts different sources of nonlinearity, such as the nonlinear magnetic characteristics of materials, non-uniform distribution of magnetic field, effects of fluid inertia, viscoplasticity, viscoelasticity, and the presence of air as a large pocket or tiny bubbles in MR dampers. Furthermore, the numerical approach has been used to interpret the reasons for a faulty behaviour that was encountered in the current research. The faulty behaviour of the damper was successfully modelled and the flow characteristics in that faulty mode were found to be significantly different from the ideal characteristics that are reported in many studies.

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Original languageEnglish
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Award date31 Dec 2020