Malcolm J. McPherson

Bio: Malcolm J. McPherson is an academic researcher from Virginia Tech. The author has contributed to research in topics: Ventilation (architecture) & Coal mining. The author has an hindex of 5, co-authored 17 publications receiving 1153 citations.

Introduction of fluid mechanics

Abstract: A fluid is a substance in which the constituent molecules are free to move relative to each other Conversely, in a solid, the relative positions of molecules remain essentially fixed under non-destructive conditions of temperature and pressure While these definitions classify matter into fluids and solids, the fluids subdivide further into liquid and gases

Refrigeration plant and mine air conditioning systems

Abstract: One of the earliest methods of temperature control in underground mines was the importation of naturally produced ice from the surface. Blocks of ice were transported in ore cars to cool miners in the Comstock Lode under Virginia City in Nevada, USA, during the 1860s. The vapour compression refrigeration cycle, currently the most widespread method of artificial cooling, appears to have first been used in mining during the 1920s. Examples included the famous Morro Velho Mine in Brazil (1923) and experimental work in British coal mines (Hancock, 1926). Air cooling techniques in mining gained further recognition in the 1930s including their utilization in the gold mines of South Africa and in the Kolar Goldfields of India. However, it was the 1960s that saw the the start of a real escalation of installed mine cooling capacity.

Physiological reactions to climatic conditions

Abstract: In conventional mining operations, the need to control air temperatures and humidities arises primarily because of the relatively narrow range of climatic conditions within which the unprotected human body can operate efficiently. In some areas of underground repositories or where remotely controlled equipment is in use, a different spectrum of atmospheric criteria may be allowed or even required. However, in this chapter, we shall concentrate on the effects of climatic variations on the human body, and alternative means of quantifying the ability of a given environment to maintain an acceptable balance between metabolic heat generation and body cooling.

Subsurface ventilation systems

Abstract: Practically every underground opening is unique in its geometry, extent, geological surroundings, environmental pollutants and reasons for its formation—natural or man made. The corresponding patterns of airflow through those openings are also highly variable. There are, however, certain features that are sufficiently common to permit classifications of structured ventilation systems and subsystems to be identified.

Radiation and radon gas

Abstract: The element uranium is widely distributed within the crust and oceans of the earth. It has been estimated that crustal rocks contain an average of some 4 g of uranium per tonne. The structure of the uranium atom is unstable; emission of subatomic particles from the nucleus causes uranium to change or decay into a new element, thorium. The process of radioactive decay continues down through a series of elements until it reaches a stable form of lead. This process has existed on earth from before the crust was formed. All forms of life on earth have evolved and exist within a constant bombardment of natural radiation including that from the uranium series of elements.

Microfluidics: Fluid physics at the nanoliter scale

Abstract: Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics

Abstract: This article reviews acoustic microfiuidics: the use of acoustic fields, principally ultrasonics, for application in microfiuidics. Although acoustics is a classical field, its promising, and indeed perplexing, capabilities in powerfully manipulating both fluids and particles within those fluids on the microscale to nanoscale has revived interest in it. The bewildering state of the literature and ample jargon from decades of research is reorganized and presented in the context of models derived from first principles. This hopefully will make the area accessible for researchers with experience in materials science, fluid mechanics, or dynamics. The abundance of interesting phenomena arising from nonlinear interactions in ultrasound that easily appear at these small scales is considered, especially in surface acoustic wave devices that are simple to fabricate with planar lithography techniques common in microfluidics, along with the many applications in microfluidics and nanofluidics that appear through the literature.

Evolution and Modern Approaches for Thermal Analysis of Electrical Machines

Abstract: In this paper, the authors present an extended survey on the evolution and the modern approaches in the thermal analysis of electrical machines. The improvements and the new techniques proposed in the last decade are analyzed in depth and compared in order to highlight the qualities and defects of each. In particular, thermal analysis based on lumped-parameter thermal network, finite-element analysis, and computational fluid dynamics are considered in this paper. In addition, an overview of the problems linked to the thermal parameter determination and computation is proposed and discussed. Taking into account the aims of this paper, a detailed list of books and papers is reported in the references to help researchers interested in these topics.

Transition from squeezing to dripping in a microfluidic T-shaped junction

Abstract: We describe the results of a numerical investigation of the dynamics of breakup of streams of immiscible fluids in the confined geometry of a microfluidic T-junction. We identify three distinct regimes of formation of droplets: squeezing, dripping and jetting, providing a unifying picture of emulsification processes typical for microfluidic systems. The squeezing mechanism of breakup is particular to microfluidic systems, since the physical confinement of the fluids has pronounced effects on the interfacial dynamics. In this regime, the breakup process is driven chiefly by the buildup of pressure upstream of an emerging droplet and both the dynamics of breakup and the scaling of the sizes of droplets are influenced only very weakly by the value of the capillary number. The dripping regime, while apparently homologous to the unbounded case, is also significantly influenced by the constrained geometry; these effects modify the scaling law for the size of the droplets derived from the balance of interfacial and viscous stresses. Finally, the jetting regime sets in only at very high flow rates, or with low interfacial tension, i.e. higher values of the capillary number, similar to the unbounded case.