Published online by Cambridge University Press: 28 July 2016
The internal motjon of a fluid assumes one or other of two distinct forms; either the elements follow one another in a direct and simple manner, or else they wander about in erratic paths as they progress downstream. In the first kind of motion, called “ regular ” or “ streamline,” the components of the velocity at any selected point are either constant, or vary in a definite manner directly related to the boundary motions. In the second, known as “ turbulent,” these components continually change in an irregular way, which cannot apparently be connected with the regular boundary motions.