Page 42 - 48Fundamentals of Compressible Fluid Mechanics

4 CHAPTER 1. INTRODUCTION

measured the choking but theoretical science did not provide explanation to it (or
was award that there is explanation for it.).
In the twentieth century the flight industry became the pushing force.
Understandably, aerospace engineering played a significant role in the develop-
ment of this knowledge. Giants like Prandtl and his students like Van Karman, as
well as others like Shapiro, dominated the field. During that time, the modern ba-
sic classes became “solidified.” Contributions by researchers and educators from
other fields were not as dominant and significant, so almost all text books in this
To add history from the work. field are written from an aerodynamic prospective.
Topics that should be in-
cluded in this history review
but that are not yet added
to this section are as fol-
lows: Multi Phase flow, cap-
illary flow and phase change.
1.3.1 Early Developments
The compressible flow is a subset of fluid mechanics/hydraulics and therefore the
knowledge development followed the understanding of incompressible flow. Early
contributors were motivated from a purely intellectual curiosity, while most later
contributions were driven by necessity. As a result, for a long time the question of
the speed of sound was bounced around.

1.3.1.1 Speed of Sound

The idea that there is a speed of sound and that it can be measured is a major
achievement. A possible explanation to this discovery lies in the fact that mother
nature exhibits in every thunder storm the difference between the speed of light
and the speed of sound. There is no clear evidence as to who came up with this
concept, but some attribute it to Galileo Galilei: 166x. Galileo, an Italian scientist,
was one of the earliest contributors to our understanding of sound. Dealing with
the difference between the two speeds (light, sound) was a major part of Galileo’s
work. However, once there was a realization that sound can be measured, people
found that sound travels in different speeds through different mediums. The early
approach to the speed of sound was by the measuring of the speed of sound.
Other milestones in the speed of sound understanding development
were by Leonardo Da Vinci, who discovered that sound travels in waves (1500).
Marin Mersenne was the first to measure the speed of sound in air (1640). Robert
Boyle discovered that sound waves must travel in a medium (1660) and this lead
to the concept that sound is a pressure change. Newton was the first to formulate
a relationship between the speed of sound in gases by relating the density and
compressibility in a medium (by assuming isothermal process). Newton’s equation
is missing the heat ratio, (late 1660’s). Maxwell was the first to derive the speed
from particles (statistical) mechanics. Therefore
some referred to coefficient
as Maxwell’s coefficient.
of sound for gas as