Application of Thermo-Fluidic Measurement Techniques

An Introduction

Tongbeum Kim, Tianjian Lu, Seung Jin Song

• Publisher: Butterworth-Heinemann
• Year: 2016
• ISBN:
  9780128098745
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

Application of Thermo-Fluidic Measurement Techniques: An Introduction provides essential measurement techniques in heat transfer and aerodynamics. In addition to a brief, but physically elaborate description of the principles of each technique, multiple examples for each technique are included. These examples elaborate all the necessary details of (a) test setups, (b) calibration, (c) data acquisition procedure, and (d) data interpretation, with comments on the limitations of each technique and how to avoid mistakes that are based on the authors' experience.

The authors have different expertise in convection heat transfer and aerodynamics, and have collaborated on various research projects that employ a variety of experimental techniques. Each author has a different view and approach to individual experimental techniques, but these views complement each other, giving new users of each technique a rounded view.

With the introduction of this valuable reference book, the reader can quickly learn both the overall and detailed aspects of each experimental technique and then apply them to their own work.

• Contains both basic principles and fundamental, physical descriptions
• Provides examples that demonstrate how each experimental technique can be used for industrial testing and academic research in heat transfer and aerodynamics
• Includes practical and in-depth examples for each technique, with comments on each experimental technique based on the authors' experiences, including limitations and trial errors with some examples of data interpretation
• Combines classical techniques in aerodynamics and conduction/convection heat transfer with modern, cutting-edge approaches
• Collates the information about various pointwise and whole field velocity and thermal measurement techniques in a single resource

Chapter 1

Experimentation in Aerodynamics and Heat Transfer

T. Kim^*

T.J. Lu^**

S.J. Song^†
* School of Mechanical and Aeronautical Engineering, University of the Witwatersrand, Johannesburg, South Africa
^** School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an, China
^† School of Mechanical and Aerospace Engineering, Seoul National University, Seoul, Korea

Abstract

For any experimental study, a fundamental question is perhaps “what to measure.” Answering this question is associated with governing equations that need to be closed. The governing equations in aerodynamics and heat transfer are the “continuity equation,” “momentum equations,” and “energy equation.” Fundamental differences in closing these equations experimentally and analytically are discussed.

Keywords

aerodynamics

calibration

heat transfer

instrumentation

measurement techniques

1.1. Introduction

Aerodynamics and heat transfer problems have been historically investigated through three different approaches: mathematical, experimental, and computational. The mathematical approach first gained popularity in the 17th, 18th, and 19th centuries through pioneers like Daniel Bernoulli, Leonard Euler, and Hermann von Helmholtz. However, the complexity of mathematical treatment combined with inadequacy at predicting basic factors like drag prompted a rise in the experimental approach. The Wright Brothers, for example, relied extensively on wind-tunnel testing in the design of their original aircraft. This trend continued through the 20th century as engineers made extensive use of experimentation in the analysis of fluid and heat transfer problems. Most recently, the cost and time requirements of experimentation have encouraged a computational approach, called “computational fluid dynamics (CFD),” to fluid and heat transfer problems in which the governing equations are solved numerically. However, the computational expense of solving the governing equations in their original form is impractical for all but the simplest configurations, leading to approximate methods of solution often including turbulence models. Furthermore, experimental data are still needed to validate the CFD results. Therefore, a sound knowledge of experimentation remains a necessary asset for not only experimentalists but also those interested in heat and fluid problems. This book provides such knowledge associated with aerodynamics and heat transfer fields. The techniques dealt with in this book are limited to those thought to be essential tools for researchers in these two disciplines.

For any experimental studies, a fundamental question is perhaps “what to measure.” Answering this question is associated with governing equations that need to be closed. The governing equations in aerodynamics and heat transfer are the “continuity equation,” “momentum equations,” and “energy equation.” These equations contain terms such as static pressure, velocity, temperature, and their gradients. The measurement techniques in this book attempt to quantify them.

On the other hand, in some cases, it is not possible, at present, to experimentally obtain the parameters required to close the above-mentioned governing equations due to experimental limitations. Furthermore, there are parameters in the governing equations that may not be experimentally quantified without compromising data quality, as could be done mathematically.

The following sections in this chapter aim not to re-derive the governing equations in aerodynamics and heat transfer but to show their physical significance.

1.2. Aerodynamics

The motion of fluid particles is governed by Navier–Stokes (N–S) equations. In addition, the fluid has ...