Hydraulic Concepts Research Articles

Enhancing the Learning of Fluid Mechanics Using Computer Simulations

AbstractThis paper reports the results of a study into the impact of computer simulations on the understanding of fluid mechanics by engineering students. A “lesson study” approach was taken, using constructivist educational theory combined with the variation theory of learning from phenomenography to inform the design of learning activities and to assess their impact. Student difficulties with fluid mechanics concepts were assessed using questions from the Fluid Mechanics Concept Inventory (FMCI). Students had the greatest difficulties with pressure measurement, fluid flow through pipes with changing diameter, and velocity profiles for fluid between flat plates. We developed a set of three simulations to address these difficulties. The impact of the simulations was gauged by a second administration of the FMCI. Most of the students in the sophomore fluid mechanics class participated in the whole of this exercise. Students showed significant improvement in two of the three areas of difficulty. Student feedback on this as an additional learning exercise was very positive.

Modeling rheological behavior of highly flowable mortar using concepts of particle and fluid mechanics

Abstract A particle–fluid model is developed for predicting the relationship between the shear stress and shear strain rate of highly flowable mortars. In this model, mortars are considered as a two-phase material, containing a fluid matrix (cement paste) and a group of well-graded, non-cohesive, and rigid particles (fine aggregate) that are uniformly distributed in the matrix. The mortar shear stress is assumed to be the sum of the shear stresses resulting from the paste flow, the aggregate particle movement, and the interaction between the cement paste and aggregate. The shear stress resulting from the paste flow is assessed using constitutive equations. The shear stress resulting from the aggregate particle movement is evaluated based on the probability and mechanical concepts of aggregate particle collision. The shear stress resulting from the interaction between the paste and aggregate is considered as the normal stress that the moving aggregate particles apply onto the cement paste. The shear rate of the mortar is obtained from the rheological definition of viscosity. Using this model, the effects of mortar mixture properties (such as aggregate size, volume, gradation, and friction as well as paste viscosity and yield stress) on mortar rheology are studied.

Wall Shear Stress: Theoretical Considerations and Methods of Measurement

In arterial blood flow, the wall shear stress expresses the force per unit area exerted by the wall on the fluid in a direction on the local tangent plane. There is substantial evidence that the wall shear stress induced by the pulsatile blood flow in the arterial system affects the atherogenic process. It is now widely accepted that the vessel segments that appear to be at the highest risk for development of atherosclerosis are those with low wall shear stress or oscillating wall shear stress. The purpose of this article is to define wall shear stress, to introduce relevant concepts of fluid mechanics to nonexperts, and to critically review the various methods that have been used for the assessment of wall shear stress in animal and human blood circulation, paying special attention to the case of coronary arteries.

Camp and Stein’s Velocity Gradient Formalization

Camp and Stein’s velocity gradient definition and its application to the study of fine sediment flocculation under flow shear are revised in the light of basic fluid mechanics concepts. Local motion and energy dissipation of a viscous fluid under laminar flow are used to prove that the Camp and Stein analysis was inaccurate for a general laminar movement. A generalization of Smoluchowski local aggregation equation and an alternative deduction for the parameter that Camp and Stein called velocity gradient are presented for a general laminar flow.

The Monge–Kantorovitch mass transfer and its computational fluid mechanics formulation

AbstractThis paper explains how computational fluid mechanics (CFM) concepts can be used to solve the Monge–Kantorovitch mass transfer type of problems (MKP). Copyright © 2002 John Wiley & Sons, Ltd.

Fluid Mechanics of DNA Double-Strand Filter Elution

Measurement of infrequent DNA double-strand breaks (DSB) in mammalian cells is essential for the understanding of cell damage by ionizing radiation and many DNA-reactive drugs. One of the most important assays for measuring DSB in cellular DNA is filter elution. This study is an attempt to determine whether standard concepts of fluid mechanics can yield a self-consistent model of this process. Major assumptions of the analysis are reptation through a channel formed by surrounding strands, with only strand ends captured by filter pores. Both viscosity and entanglement with surrounding strands are considered to determine the resistance to this motion. One important result is that the average elution time of a strand depends not only on its length, but also on the size distribution of the surrounding strands. This model is consistent with experimental observations, such as the dependence of elution kinetics upon radiation dose, but independence from the size of the DNA sample up to a critical filter loading, and possible overlap of elution times for strands of different length. It indicates how the dependence of elution time on the flow rate could reveal the relative importance of viscous and entanglement resistance, and also predicts the consequences of using different filters.

On the circular hydraulic jump

We study both experimentally and theoretically the classical problem of the circular hydraulic jump. By means of elementary hydrodynamics we investigate the scaling laws governing the position of the hydraulic jump and compare our predictions with experimental data. The results of our simple model are in good agreement with the experiments and with more elaborate approaches. The problem can be effectively used for educational purposes, being appropriate both for experimental investigations and for theoretical application of many fluid mechanics concepts.

97/00598 Background carbon-14 levels in UK foodstuffs, 1981–1995, based upon a 1992 survey

The irreversibilities originating from finite-time and finite-size constraints are important in the real thermal system optimization. Since classical thermodynamic analysis based on thermodynamic equilibrium do not consider these constraints directly, it is necessary to consider the energy transfer between the system and its surroundings in the rate form. Finite-time thermodynamics provides a fundamental starting point for the optimization of real thermal systems including the fundamental concepts of heat transfer and fluid mechanics to classical thermodynamics. In this study, optimization studies of thermal systems, that consider various objective functions, based on finite-time thermodynamics and thermoeconomics are reviewed.

Entropy generation minimization: The new thermodynamics of finite-size devices and finite-time processes

Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite-size and finite-time constraints. The review traces the development and adoption of the method in several sectors of mainstream thermal engineering and science: cryogenics, heat transfer, education, storage systems, solar power plants, nuclear and fossil power plants, and refrigerators. Emphasis is placed on the fundamental and technological importance of the optimization method and its results, the pedagogical merits of the method, and the chronological development of the field.

A laboratory experiment for measuring the free convection heat transfer coefficient of a plane metal plate

An experiment is proposed for university science students with the aim of measuring the free convection heat transfer coefficient of a heated metal plate, by means of holographic interferometry. In the course of the experiment the students deal with concepts in fluid mechanics, holography, image analysis and computers.

Turbulent mixing in estuaries

Abstract The pattern of flow in a tidal estuary is largely determined by the vertical transport of momentum and density due to turbulence. In a well-mixed estuary the turbulent mixing throughout the depth is dominated by turbulence associated with friction at the bed, although the effect of shear at mid-depth due to the density driven residual flow is not necessarily negligible. The main features of the flow resemble those in boundary layer flows, on which much information is available from other branches of fluid mechanics. Similar methods of calculation may be used, based on a mixing length approach or a turbulent energy closure model. In a slightly stratified estuary the conditions are modified without being changed radically, but as the opposite extreme of a highly stratified estuary is approached the flow is better represented by two well-mixed layers, separated by a relatively thin shear layer in which there is a steep density gradient. This type of flow has received considerable attention in theoretical studies and laboratory experiments and the results have some application to estuarine flows. Recent work on the application of relevant concepts of fluid mechanics to flows in estuaries is reviewed and some suggestions made for lines of future research. In many tidal estuaries the position is complicated in that the flow may vary between well-mixed and stratified within a tidal cycle and attention should be given to the time-varying nature of the flow. Even if only the tidally averaged result of mixing is required, a knowledge of the changing physical processes is needed in order to parameterize their effects.

Energy from the wind

The large-scale generation of electrical power by wind turbine fields is discussed. It is shown that the maximum power which can be extracted by a wind turbine is 16/27 or 59.3% of the power available in the wind. An estimate is made of the total electrical power which could be generated in the United States by utilizing wind energy. The material in this paper was presented by the authors in a one-semester course on energy science. It could also be used in an introductory physics class as an illustration of elementary fluid mechanics concepts and of the basic principles of energy and momentum conservation.

Analysis of groundwater flow : London: Arnold, 1976, 214P

The aim of the book is to introduce the student to the analysis of groundwater flow. The broad field of the physics of flow through porous media is surveyed briefly, but the greater part of the book is concerned with simple analytical techniques. Familiarity with basic fluid mechanics concepts is assumed. The emphasis is on the potential flow analogy. In numerical work, SI units are used. After a general introductory survey of the problems and the physical processes involved, chapters are as follows: equation of continuity, steady confined flow, flow nets derived from curvilinear coordinates, steady unconfined flow, unsteady groundwater flow, flow in leaky aquifers, unsteady flow in unconfined aquifers, salt water interfaces. The book will principally be of interest to final year and postgraduate students of civil engineering, practising engineers and hydrologists. /TRRL/

Mass transport of ATP within the motile sperm

Mathematical models are developed to determine if molecular diffusion is an adequate mechanism for transport of ATP from the sperm midpiece along the length of the tail where it is consumed to produce the necessary energy for motility. Previous work in this area has been based on steady state assumptions and assumed reaction kinetics for the consumption of ATP along the length of the tail. In this work, the reaction kinetics are deduced indirectly from the expenditure of elastic and viscous energy as a function of time and position; these deductions are made from fundamental concepts of fluid mechanics and beam mechanics applied to sperm waveforms experimentally determined by others. The models are tested for bull sperm and sea urchin sperm of the genus Psammechinus miliaris, for which the waveform was mathematically characterized. The model results indicated a concentration of ATP that was positive over the entire flagellar length for all times. Whether molecular diffusion is an adequate transport mechanism to supply the required ATP can be reduced to the computation of a dimensionless parameter developed here.

A mathematical model for the elastic and fluid mechanical behavior of the human eye.

A simplified mathematical model for the eye is proposed. This idealized model simulates the aquaous flow and intraocular pressure behavior of the human eye. Starting from elementary concepts in elasticity and fluid mechanics, one can derive differential equations governing the behavior of the mathematical model. When integrated, these equations yield algebraic relationships which are closely related to some of the widely used empirical formulae in ophthalmology, e.g., Friedenwald's (1948) formula for the scleral rigidity coefficient and Grant's (1950) equation for the facility of aqueous outflow. The eye's intraocular pressure variations are simply related to its aqueous and blood volume changes if one assumes that ocular tissue has essentially linear elastic properties. St. Helen's and McEwen's (1961) experiments indicate that a linear approximation is reasonably accurate if the standard Hookian stress strain law is modified to take into account the anelastic or time-dependent elastic behavior of the corneo-scleral membrane. The last part of the paper discusses transient phenomena in an externally disturbed eye, e.g., when a tonometer is applied. One important result is a theoretical equation to describe the mean curve that one records in a tonographic tracing. This paper represents the first attempt to formulate a mathematical model relating the over-all elastic and fluid mechanical behavior of the eye. It is hoped that the model will stimulate interst and prove useful to the medical profession in motivating future experiments and in suggesting improvements for existing empirical formulae.

Concepts of Fluid Mechanics Provided by Primary Sedimentary Structures

ABSTRACT Primary sedimentary structures can be used to infer conditions of flow which prevailed within fluid currents which deposited the sediment. Three particularly important conclusions about fluid flow conditions can be drawn from primary sedimentary structures: 1) The mechanisms of suspension and traction, as defined by G. K. Gilbert in 1914, are fundamentally different, and can be recognized by the different gross structures which they produce in sediments, and by the different effects which are brought about by the distinctive paths followed by particles which move under the influence of each mechanism; 2) The effects of grain-to-grain encounters in cohesionless sediment, which arise in response to current flow, can also be recognized in primary sedimentary structures, as can analogous ffects in cohesive sediments; and 3) Mass shearing effects at the fluid-sediment interface may produce deformation in cohesive sediments. The interpretations of primary sedimentary structures summarized herein suggest new lines of experimental investigation of fluids and sediments, in which attempts should be made to duplicate some of the mass shearing effects which have been recognized in cohesive sediments found in nature.

Mechanics of Evapo-Transpiration

Fundamental mechanisms involved in transpiration and evaporation are analyzed; manner in which physical factors in these mechanisms act to determine instantaneous transpiration rate, are examined by use of concepts of fluid mechanics; these factors are expressed in Darcy’s law, continuity equation, and power equation; variables in these equations are functions of soil, plant, and weather factors.

A Method for Calculating Multi-Dimensional Immiscible Displacement

Published in Petroleum Transactions, AIME, Vol 216, 1959, pages 297–308. Paper presented at 34th Annual Fall Meeting of Society of Petroleum Engineers at Dallas, Tex. Oct. 4–7, 1959. ABSTRACT A numerical solution of equations describing two-phase flow in porous media shows promise in providing a technique for predicting the displacement from sands of oil by water or gas. The description includes the influence of relative permeability, fluid viscosities and densities, gravity, and capillary pressure, and, though tested only for two-dimensional cases, should be equally applicable in three-dimensional geometry. Two numerical methods are presented: the first method is quite general in its applicability; the second method can be used only with certain types of boundary conditions but requires less computing. Comparisons of computed results with data from laboratory models are presented. These data were taken on a water flood of a stratified model and on water floods of a five-spot model for favorable and unfavorable mobility ratios. On the stratified model, excellent agreement with recovery at breakthrough was obtained; agreement with recovery after breakthrough was poor. In the five-spot model, good agreement was obtained with recovery at and after breakthrough. INTRODUCTION The purpose of this paper is twofold; first, to present a reservoir engineering method requiring knowledge only of rock geometry and the normally measured rock and fluid properties for calculating the multi-dimensional flow of water displacing oil from porous, water-wet rock containing connate water; and, second, to investigate the validity of the method by comparing results of calculations with previously observed displacements in laboratory models. The availability of such a verified technique of reservoir analysis would afford major advantages. First, it would demonstrate that the fundamental macroscopic concepts of two-phase fluid mechanics, i.e., relative permeability and capillary pressure, yield an adequate description of the physical process.

Fundamental aspects of solids‐gas flow: Part I: Introductory concepts and idealised sphere motion in viscous regime

AbstractThis article introduces a series of analytical and critical literature surveys which deal first with the individual fundamental momentum transfer phenomena associated with particulate motion as affected by particle shape, roughness, acceleration, concentration and rotation, as well as the turbulence characteristics and boundary conditions of the transporting fluid. This information will then be used as a basis of discussion and interpretation of the many investigations of multiparticle solids‐gas conveying systems and contacting techniques reported in the literature.This first paper reviews briefly some pertinent basic concepts of fluid mechanics, and then considers the development of the fluid velocity field and drag for single spherical particles moving rectilinearly at pre‐wake‐forming Reynolds Numbers through an infinite and undisturbed fluid.