The earlier experiments on the fluid friction were conducted by ‘Froude who concluded that:
1. The frictional resistance varies approximately with the square of the velocity of the liquid.
2. The frictional resistance vanes with th nature of the surface.
Later on, some experiments formulae were derived for the loss of head due to friction, out of which the following two’ are important from the subject point of view:
1. Darcy’s formula for loss of head in pipes, and
2. Chezy’s formula for loss of head in pipes Chezy’s formula for loss of head in pipes Darcy Formula for loss of head in pipe Hydraulic Gradient Line If pressure heads (i.e., p/w) of a liquid flowing in a pipe be plotted as vertical ordinates on the centre line of the pipe, then the line joining the tops of such ordinates is known as hydraulic gradient line (briefly written as H.G.L.)
If the sum of pressure heads and velocity heads (P/w + V2/2g flowing m a pipe be plotted as vertical ordinates on the centre line of the pipe, then the line joining the tops of such ordinates is known as total energy line (briefly written as T.E.L.)
Or, in other words, the total energy line lies over the hydraulic gradient by an amount equal to the velocity heads.
Note : The above mentioned two lines give very useful information regarding the flow of liquid in the pipeline. Some of them will be discussed in the following pages.
No comments:
Post a Comment