Fluid Mechanics Measurements

R. Goldstein

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781351447829
• Edition: 2
• Topic: Technologie et ingénierie
• Subtopic: Génie mécanique

This revised edition provides updated fluid mechanics measurement techniques as well as a comprehensive review of flow properties required for research, development, and application. Fluid-mechanics measurements in wind tunnel studies, aeroacoustics, and turbulent mixing layers, the theory of fluid mechanics, the application of the laws of fluid mechanics to measurement techniques, techniques of thermal anemometry, laser velocimetry, volume flow measurement techniques, and fluid mechanics measurement in non-Newtonian fluids, and various other techniques are discussed.

CHAPTER
ONE

WHAT DO WE MEASURE, AND WHY?

Roger E. A. Arndt

1.1 INTRODUCTION

The purpose of this chapter is to acquaint the reader with the need for flow measurements, to provide some insight concerning various applications, and to introduce the methodology and philosophy of flow measurements. A distinction is drawn between measurements having direct application (e.g., flow rate in a pipe) and measurements that are used indirectly for the correlation of primary data, for the verification of theory, and for the tuning of mathematical models. Some emphasis is placed on the need to understand fluid mechanics for the design of experiments, for the interpretation of results, and for estimating deterministic errors due to flow modification by instrumentation placed in the flow. Examples of diagnostic techniques in research problems are drawn from various fields. The principles of fluid mechanics are reviewed to demonstrate the need for measurements, as well as to provide a basis for describing various systematic errors inherent in flow measurement devices.

Various limitations on flow measurement techniques are described in general terms. The need to understand the trade-off between temporal response and spatial resolution in a flowing system is underscored. Finally, an overview of data analysis is given to provide the reader with some insight into the interrelationship between the flow field, the measurement device, and the results.

The details of actual measurement techniques and data reduction are given in following chapters.

1.2 THE NEED FOR FLOW MEASUREMENTS

It would be impossible in this chapter to describe all the various types of flow measurements and their applications. However, an attempt is made to describe the overall methodology and philosophy of fluid measurement techniques and their application. One can think of several general needs for flow measurements. In some cases, the data are useful of themselves, as for example, the rate of flow in a pipe or the mass flux of contaminants in a river. In these cases, the flow quantity desired could be measured either directly or indirectly and it would be the final result. In other cases, flow measurements are...