ABSTRACT
In turbulent flow , the progression of the fluid particles is irregular and there is a seemingly haphazard interchange of position. Individual particles are subject to fluctuating transverse velocities so that the motion is eddying and sinuous rather than rectilinear. If dye is injected at a certain point, it will rapidly diffuse throughout the flow stream. In the case of turbulent flow in say a pipe, an instantaneous recording of the velocity at a section would reveal a distribution somewhat as indicated in Fig. 4.1(a). The steady velocity, as would be recorded by normal measuring instruments, is indicated in dotted outline, and it is apparent that turbulent flow is characterised by an unsteady fluctuating velocity superimposed on a temporal steady mean.
