Inhaltsangabe:Introduction: In experimental fluid dynamic measurements hot-wire anemometry is used to record information about flow fields. Furthermore one can obtain the magnitude, the direction and even the time dependant behaviour of the fluid flow, if multiple-wire probes are in operation. The hot-wire measurement technique is based on the convective heat transfer from a heated element to the fluid flow, which is actually proportional to the velocity of the flow. So HWA is an indirect measurement technique. There are miscellaneous sensors which work properly in water or other liquids, air or in gas flows. As an example, Fig. 1.1 shows a cross-wire probe in a fluid flow, which can detect the velocity and its direction in two components, if the main flow direction is in one plane (2D flow). Predominantly HWA is a research tool for turbulent flow studies, especially transient procedures. Turbulence models have to be built to represent the characteristics of the flow in numerical simulations (CFD). Therefore only detailed experimental measurements lead to reliable information about the local velocity of a turbulent flow. This can be provided by HWA on the basis of its very high spatial and temporal resolution. Although the development of HWA started at the beginning of the 19th century and new techniques like PIV or LDA (direct methods) have been established, it is still a common device in all wind tunnel labs. The analogue output signal can be optimized by filters before signal processing. It can also be deployed to arrange a spectrum analysis, due to the high temporal resolution. Moreover, unlike the digital devices the analogue signal is densely packed. The range of application is large and leads from sub- and supersonic flows, the independency of the medium to high-temperature measurements. HWA is also affordable in contrast to LDA and PIV systems. In spite of these advantages the natural contamination of the hot-wire probe increases by and by, since the particles in the fluid flow mature themselves to the probe and finally isolate it. As this effect of disturbance causes measuring errors, the hot-wire probes have to be calibrated at frequent intervals - best before and after every data acquisition series. However, HWA is an intrusive measurement technique, thus disturbing the flow. Another disadvantage is that it is not applicable in separation and backward flow regions. The aim of this thesis is to develop an automated calibration system to [...]

The contributing authors have been chosen because of their depth of knowledge and experience in air pollution work, and we are confident that this is reflected in a Handbook which will find very wide application wherever air pollution analysis is practised. Roy M. Harrison Roger Perry February 1985 Readers are recommended to follow all the usual laboratory safety pre cautions. While care has been taken to ensure that the information in this book is correct, neither the authors nor the publisher can accept responsibility for any outcome of the application of methods and procedures outlined in this book. Contributors A. Apling BSc, PhD Air Pollution Division Warren Spring Laboratory Gunnels Wood Road Stevenage Hertfordshire SG 1 2BX UK H.W. de Koning DSc Environmental Pollution Division of Environmental Health World Health Organization Geneva Switzerland R.M. Harrison PhD Department of Chemistry University of Essex Wivenhoe Park Colchester C04 3SQ UK P.W.W. Kirk BSc, MSc, PhD, DIC, C Chern, MRSC Department of Civil Engineering Imperial College London SW7 2BU UK J.R. Kramer Professor in Geochemistry Department of Geology McMaster University Hamilton Ontario L8S 4Ml Canada J.N. Lester B. Tech, MSc, DIC, PhD, MIPHE, Department of Civil Engineering Imperial College London SW7 2BU UK xxi xxii Contributors A.E. Mcintyre BSc, PhD, DIC, MIWES Consultants in Environmental Sciences Ltd Yeoman House 63 Croydon Road London SW20 7TW UK D.J.

A comprehensive and practical book that examines this very important technique used in fluid flow measurements. As well as the physical experimental set-ups and techniques the book deals with the analysis of the signals gathered from HWA probes.

Weighing in on the growth of innovative technologies, the adoption of new standards, and the lack of educational development as it relates to current and emerging applications, the third edition of Introduction to Instrumentation and Measurements uses the authors’ 40 years of teaching experience to expound on the theory, science, and art of modern instrumentation and measurements (I&M). What’s New in This Edition: This edition includes material on modern integrated circuit (IC) and photonic sensors, micro-electro-mechanical (MEM) and nano-electro-mechanical (NEM) sensors, chemical and radiation sensors, signal conditioning, noise, data interfaces, and basic digital signal processing (DSP), and upgrades every chapter with the latest advancements. It contains new material on the designs of micro-electro-mechanical (MEMS) sensors, adds two new chapters on wireless instrumentation and microsensors, and incorporates extensive biomedical examples and problems. Containing 13 chapters, this third edition: Describes sensor dynamics, signal conditioning, and data display and storage Focuses on means of conditioning the analog outputs of various sensors Considers noise and coherent interference in measurements in depth Covers the traditional topics of DC null methods of measurement and AC null measurements Examines Wheatstone and Kelvin bridges and potentiometers Explores the major AC bridges used to measure inductance, Q, capacitance, and D Presents a survey of sensor mechanisms Includes a description and analysis of sensors based on the giant magnetoresistive effect (GMR) and the anisotropic magnetoresistive (AMR) effect Provides a detailed analysis of mechanical gyroscopes, clinometers, and accelerometers Contains the classic means of measuring electrical quantities Examines digital interfaces in measurement systems Defines digital signal conditioning in instrumentation Addresses solid-state chemical microsensors and wireless instrumentation Introduces mechanical microsensors (MEMS and NEMS) Details examples of the design of measurement systems Introduction to Instrumentation and Measurements is written with practicing engineers and scientists in mind, and is intended to be used in a classroom course or as a reference. It is assumed that the reader has taken core EE curriculum courses or their equivalents.

This 1985 book provides a summary of the theory and practice of the hot wire anemometer, an instrument used to measure the speed of fluid flow. Many techniques and uses of this instrument are discussed in detail. The author considers such topics as probe fouling, probe design, and circuit design, as well as the thermodynamics of heated wires and thin films. He also discusses measurements of turbulence, shear flows, vorticity, temperature, combined temperature and velocity, two-phase flows, and compressible flows for measurements in air, water, mercury, blood, glycerine, oil, luminous gases, and polymer solutions. The book concludes with a section on the pulsed wire anemometer and other wake-sensing anemometers. This book assumes a familiarity with basic fluid mechanics. However, mathematical descriptions occur near the end of each chapter thus allowing those with a limited mathematical background to make use of the practical details at the beginning of each chapter.

A brand-new edition of the classic guide on low-speed wind tunnel testing While great advances in theoretical and computational methods have been made in recent years, low-speed wind tunnel testing remains essential for obtaining the full range of data needed to guide detailed design decisions for many practical engineering problems. This long-awaited Third Edition of William H. Rae, Jr.'s landmark reference brings together essential information on all aspects of low-speed wind tunnel design, analysis, testing, and instrumentation in one easy-to-use resource. Written by authors who are among the most respected wind tunnel engineers in the world, this edition has been updated to address current topics and applications, and includes coverage of digital electronics, new instrumentation, video and photographic methods, pressure-sensitive paint, and liquid crystal-based measurement methods. The book is organized for quick access to topics of interest, and examines basic test techniques and objectives of modeling and testing aircraft designs in low-speed wind tunnels, as well as applications to fluid motion analysis, automobiles, marine vessels, buildings, bridges, and other structures subject to wind loading. Supplemented with real-world examples throughout, Low-Speed Wind Tunnel Testing, Third Edition is an indispensable resource for aerospace engineering students and professionals, engineers and researchers in the automotive industries, wind tunnel designers, architects, and others who need to get the most from low-speed wind tunnel technology and experiments in their work.