DYNA JOURNAL ENGINEERING

Key words:

canal, radio hidráulico, caudal, presión, velocidad, pérdida de carga, fórmula, tubería, channel, hydraulic radio, flow, pressure, speed, loss of load (cargo), formula and pipeline.

Article type:

AULA DYNA / DYNA CLASSROOM

Section:

LEARNING EVERY DAY

In the present study we offer Chèzy's C coefficient values based on the different values of R (average hydraulic radius) and the coefficient of the roughness of the walls and bottom, as well as Fanning's corresponding values of the coefficient. This is done for the five classical formulas made by Ganguillet and Kütter (simplified), Manning-Strickler, Bazin, Koeschlin and Forchheimer.
Written in function of , on the other hand, the Darcy-Weisbach formula can be applied directly without the aid of other empirical data. Finally, the author proposes twelve formulas to calculate these channels according to the different frictions, together with a multiple model of universal application.
The testing of statistical hypotheses probably constitutes the most fertile contribution of the statistical-mathematical methods to accept o to refuse hypothesis and theories in any scientific field that has to be contrasted to reality, and also to solve less scientific but of undoubted practical value problems as those involved in Hydrology and Hydraulics.
All these considerations were already taken into account by the author in his previous book called "Cinco temas de Hidrología e Hidráulica" in which in Chapter I, several formulas for the calculus in free conductions were used following the statistical methodology. Those formulas are now the basis to calculate new ones adapted to forced, or under pressure, conductions. In this case the author is not using a unique formula, but he proposes a different one for each type of material, in order to achieve more accurate calculations. The formulas are established in accordance with six categories of roughness and five intermediate.
To reinforce this line of work, a test was performed in three different pipes (PVC, HDPE and asbestos-cement), studying the theoretical values of a group of hydraulic parameters both with universal used formulas and with those here proposed. The experiment clearly showed that these formulas gave better results in the calculus and the measuring of the real values for forced conductions.