THE EVOLUTION OF AERODYNAMICS IN THE TWENTIETH-CENTURY:. ENGINEERING OR SCIENCE?

INTRODUCTION

The field of aerodynamics is frequently characterized as an applied science. This appellation is simplistic, and is somewhat misleading; it is not consistent with the engineering thought process so nicely described and interpreted by Vincenti.1 The intellectual understanding of aerodynamics, as well as the use of this understanding in the design of flight vehicles, has grown exponentially during the twentieth – century. How much of this growth can be called “science”? How much can be called “engineering”? How much falls into the grey area called “engineering science”? The purpose of this paper is to address these questions. Specifically, some highlights from the evolution of aerodynamics in the twentieth-century will be discussed from an historical viewpoint, and the nature of the intellectual thought processes associated with these highlights will be examined. These highlights are chosen from a much broader study of the history of aerodynamics carried out by the author.2

For the purpose of this paper, we shall make the distinction between the roles of science, engineering, and engineering science as follows.

Science: A study of the physical nature of the world and universe, where the desired end product is simply the acquisition of new knowledge for its own sake.

Engineering: The art of applying an autonomous form of knowledge for the purpose of designing and constructing an artifice to meet some recognized need.

Engineering Science: The acquisition of new knowledge for the specific purpose of qualitatively or quantitatively enhancing the process of designing and constructing an artifice.

These distinctions are basically consistent with those made by Vincenti.3

There is perhaps no better example of the blending of the disciplines of science, engineering science, and pure engineering than the evolution of modem aerodynamics. The present paper discusses this evolution in five steps: (1) the total lack of technology transfer of the basic science of fluid dynamics in the nineteenth century to the design of flying machines at that time (prior to 1891); (2) the reversal of this situation at the beginning of the twentieth century when academic science discovered the airplane, when the success of Lilienthal and the Wright brothers

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P Galison and A. Roland (eds.), Atmospheric Flight in the Twentieth Century, 241-256 © 2000 Kluwer Academic Publishers.

proved the feasibility of the flying machine, and when academicians such as Kutta and Joukowski developed the seminal circulation theory of lift and Prandtl introduced the concept of the boundary layer, all representing the introduction of engineering science to the study of aerodynamics (1891 – 1907); (3) the era of strut and wire biplanes, exemplified by the aerodynamic investigation of Eiffel, who blended both engineering science and engineering in his lengthy wind tunnel investigations (1909 – 1921); (4) the era of the mature propeller-driven airplane, characterized by the evolution of streamlining, representing again both engineering science and engineering; (5) the era of the modem jet propelled airplane, including the revolutionary development of the swept wing (see also the companion paper in this volume, “Engineering Experiment and Engineering Theory: The Aerodynamics of Wings at Supersonic Speeds, 1946 – 1948,” by Walter Vincenti). In the final analysis, we will see that the naive “engineering versus science” alluded to in the title of this paper fails to hold up, because the evolution of aerodynamics in the twentieth century was characterized by a subtle integration of both.