Introduction

It is evident that the treatment of channels and Froude’s work on ships were conducted in the same way as one might explore some new territory by the obvious method of going to see what is there. At the very least, in science, some means of exploration that was a little less dependent on trial was needed. Froude had shown that for the troublesome problem of ship resistance where there is viscous friction and wave-making operating together there is an underlying order so there was every reason to expect to find order throughout the science of fluid flow. To some extent there was already some order in what has become known as the physical properties of fluids, for example, density, viscosity and surface tension, and these had been expressed in terms of more fundamental units of mass, length and time. It was the relationship between these physical properties and the spatial properties of the system like length and diameter and speed that was not clear.

 

It must have been apparent that a whole science was growing up that was centred on the flow of water and air round and through all sorts of solid bodies, for example ships and channels. That science would depend on the intelligent use of Newton’s laws, mathematics and experiment and Froude had shown that all three used together were very powerful indeed. One might add that attempts to use experiment alone have not produced a coherent body of knowledge[1] and nor have attempts to use mathematics alone.[2] 

 

I have described Rayleigh’s contribution to this process in Chapter 7 pages 8 to 10. Now I want to explain dimensional analysis as a fall-out from Rayleigh.