Page 63 - 48Fundamentals of Compressible Fluid Mechanics

3.1 Motivation

In tradition compressible flow classes there is very little discussion about speed
of sound outside the ideal gas. This author think that approach has many short-
1
comings. In recent consultation an engineer A design of industrial system that
contains converting diverging nozzle with filter to remove small particles from air.
The engineer was well aware about the calculation of the nozzle. Thus, engineer
was able to predict that was a chocking point. Yet, the engineer was not ware what
is the effect of particles on the speed of sound. Hence, the actual flow rate was
only half of his prediction. As it will shown in this chapter, the particles reduces the
speed of sound by almost half. With the “new” knowledge of the consultation the
calculations were within the range of acceptable results.
The above situation is not unique in the industry. It should be expected
that engineers know how to manged this situation of non pure substances (like
clean air). The fact that the engineer know about the chocking is great but it is
2
enough for today sophisticated industry . In this chapter an introductory discussion
about different situations that can appear the industry in regards to speed of sound.

3.2 Introduction

1 Aerospace engineer that alumni of University of Minnesota.
2 Pardon, but a joke is must in this situation. A cat is pursuing a mouse and the mouse escape and
hide in the hole. Suddenly, the mouse hear a barking dog and a cat yelling. The mouse go out to
investigate, and cat is catching the mouse. The mouse ask the cat I thought I hear a dog. The cat reply,
yes you right. My teacher was right, one language is not enough today.

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