Chezy formula

Turbulent flow in open channels (or part-filled pipes) behaves approximately as flow in full, circular pipe flow of the same hydraulic radius. On this basis we can rearrange the Farming friction formula (see p. 157) into the format of the Chezy formula... 

The Manning formula can be derived from the Chezy formula by assuming that / is inversely proportional to Ri. The roughness factor n can be taken as 0.012 for reasonably smooth steel pipes when SI units are used. For the case above... 

Chezy formula A semi-empirical formula that relates the rate of discharge of liquid in an open channel to its dimensions, slope, and surface roughness as Q = CA-JrM where C is the Ch zy coefficient, A is the cross-sectional area of the channel, m is the mean hydraulic diameter, and i is the slope of the channel. The formula was devised by French engineer Antoine Ch zy (1718-98) who was responsible for designing a canal system to supply water to Paris. The Ch zy coefficient was developed further in 1890 by Irish engineer Robert Manning (1816-97). See manning formula. 

In 1775 Chezy proposed that the velocity in an open channel varied as (RS)y2, which led to the formula... 

Of course, this type of solution is not restricted to the Manning formula. Equation (10.124) may be replaced with a similar relation based on a constant value of the Chezy C or on a value that varies with R in accordance with Eq. (10.124). 

The Manning formula represents an attempt to refine the Chezy equation in terms of the constant C ... 

The Chezy coefficient depends on the channel wall roughness and the hydraulic radius, and can be calculated from formulae in standard books on fluid mechanics. In practical terms H will be much less than Hb, so as a first approximation H Hb-... 

The Chezy coefficient is a function of channel roughness, but also depends somewhat on channel geometry. Several empirical formulae have been developed to estimate values of Ccz- Among these formulae, one of the simplest and most widely used is that developed by Robert Manning, in which Ccz is proportional to divided by a chaimel rough-... 

---