A Mathematical Model and Numerical Simulations of Redox Electrochemical Systems with MHD and Natural Convection

A comprehensive mathematical model for redox electrochemical systems with magnetohydrodynamics (MHD) and natural convection are presented. The model is based on density changes in isothermal systems that accompany redox reaction at the electrode due to supporting electrolyte ions migrating into and out of the diffusion layer to satisfy electroneutrality. Numerical simulations have been performed for an axisymmetric, milli-electrode electrochemical cell with gravity directed along the axis in both directions to investigate the effect of the electrode orientation with respect to gravity. Results show that natural convection is significant in both cases, with the maximum velocity being an order of magnitude higher when it forms a jet-like flow away from the electrode, compared to the case when the gravity direction is switched causing the fluid to flow toward the electrode. The electrode currents also show similar trend showing a higher current when gravity is directed toward the working electrode

Transient CFD simulations of pumping and mixing using electromagnetic

In this dissertation, two dimensional and three dimensional, transient CFD simulations are conducted to investigate the active pumping and mixing in microfluidics driven by Electromagnetic/Lorentz force. Shallow disk/ring cylindrical microfluidic cell and shallow cuboid microfluidic cell with electrodes deposited on the bottom surface are modelled for mixing and pumping purposes respectively. By applying voltage across specific pair of electrodes, an ionic current is established in the weak conductive liquid present in the cell. The current interacts with an externally applied magnetic field generating a Lorentz force that causes fluid motion in the cell. Velocity vectors, electric potential distributions and ionic current lines are presented with high resolution in post-processing techniques. By switching on and off a pair of electrode, a blinking vortex is generated to induce the chaotic advection so as to enhance the mixing quality. Various particle trajectories based analyses using extensive post-processing of the simulation results show that the period T plays an important role in generating chaotic advection. Conducting polymer modified electrodes in microfluidics are also modeled and studied to build the bridge between the electrochemical properties of conducting polymer film and MHD flow manipulations in microfluidics. This dissertation establishes CFD simulation of MHD flow as a robust tool to study pumping and mixing in a microfluidic cell. The techniques developed in the present work are also applicable in MHD flow control in microfluidics --Abstract, page iii

Clinical translation of biomedical materials and the key factors towards product registration

Biomedical materials have been developed for facilitating tissue regeneration and healing enhancement. Although research on biomedical materials has made great progress in material innovation and preclinical testing, the bottleneck is their translation from research and development to clinical applications; that is, the current rate of product registration and industrialization is low, which directly affects their clinical applications. In this paper, we introduce the basic features of biomedical materials towards the making of medical products and the experiences of our group in research and clinical translation of biomaterials for bone-tissue regeneration in the last few years. Based on our experience, we propose that the translational medicine platform (TMP) is an effective route to facilitate the progress of biomedical materials from bench to bedside. Moreover, from the viewpoints of scientific technology and management, the functions of TMP were also addressed. Relationships among TMP, research institution, enterprise, and government were also explored from the viewpoints of technological innovation, chemical engineering integration, fund raising, and management. This paper provides a theoretical and practical reference for clinical translation of biomedical materials

Dynamic Structural Responses of Long-Span Dome Structures Induced by Tornadoes

Long-span dome structures are widely used for public assembly venues because of their large column-free space and efficient use of materials. When occupied by hundreds or even thousands of people, it would be devastating if they fail or collapse, which unfortunately happen frequently during extreme events, especially under tornadic winds. Although static effects of tornadoes on civil structures have been extensively studied, their dynamic impact has not been sufficiently investigated. In this study, non-stationary characteristics of tornadoes and their dynamic impact on a long-span dome structure are systematically investigated. In particular, the time-variant wind pressure on the dome surface induced by translating tornadoes with different intensities is characterized through Computational Fluid Dynamics simulations. The obtained wind pressure is then mapped onto the finite element model of the dome structure, and transient time-history analyses are conducted to characterize the tornado-induced dynamic responses. It is observed that non-stationary wind pressure and the induced dynamic structural responses are significant, when core radius of the tornado approaches the dome. Wind flow of EF4 and EF5 tornadoes is found to be more turbulent than EF2 and EF3 tornadoes, and hence larger and more rapid fluctuations of dynamic responses

Dust Suppression Analysis of a New Spiral Hopper Using CFD-DEM Simulations and Experiments

A new dust suppression hopper with a spiral guide plate embedded in the conventional hopper is proposed for the dust suppression of hopper transfer processes in this article. The Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling numerical method is used to investigate the particle motion and flow field distribution of the hopper transfer process. The experiment is undertaken to determine dust suppression performance. The results show that the maximum particle velocity for the spiral hopper is dropped by 1.6 m/s compared to the conventional hopper, which means the collision of the particles and the spiral hopper is weakened. The axial airflow velocity of the spiral is reduced. In addition, the maximum dust concentration of the spiral hopper inlet is reduced by 56.9% due to the impact velocity of particles is small, and the secondary fugitive dust is controlled inside a semi-closed space formed by the spiral guide plate. It is thus concluded that the spiral hopper provides an effective way in dust control

Modelling Translating Tornado-Like Wind Flow using CFD Simulations

This study investigates and compares two different strategies to simulate the translating motion of tornadoes, which are to establish the relative motion between the tornado and the ground, or to move the swirling wind flow directly. To be specific, two approaches based on the two different strategies are applied to model the translating motion of the tornado-like wind flow. By comparing the generated overall and near-ground wind flow with the real-world tornadoes, the proper way to simulate the translation of tornadoes is determined