 THE HYDRAULICS OF OPEN CHANNEL FLOW

INTRODUCTION OF THE HYDRAULICS OF OPEN CHANNEL FLOW :

PRESENTATION : The term ‘hydraulics’ is related to the application of the Fluid Mechanics principles to water engineering structures, civil and environmental engineering facilities, especially hydraulic structures (e.g. canal, river, dam, reservoir and water treatment plant). In the book, we consider open channels in which liquid (i.e. water) flows with a free surface. Examples of open channels are natural streams and rivers. Man-made channels include irrigation and navigation canals, drainage ditches, sewer and culvert pipes running partially full, and spillways.

The primary factor in open channel flow analysis is the location of the free surface, which is unknown beforehand (i.e. a priori). The free surface rises and falls in response to perturbations to the flow (e.g. changes in channel slope or width). The main parameters of a hydraulic study are the geometry of the channel (e.g. width, slope and roughness), the properties of the flowing fluid (e.g. density and viscosity) and the flow parameters (e.g. velocity and flow depth).THE HYDRAULICS OF OPEN CHANNEL FLOW

FLUID PROPERTIES : The density(p) of a fluid is defined as its mass per unit volume. All real fluids resist any force tending to cause one layer to move over another, but this resistance is offered only while the movement is taking place. The resistance to the movement of one layer of fluid over an adjoining one is referred to as the viscosity of the fluid. Newton’s law of viscosity postulates that, for the straight parallel motion of a given fluid, the tangential stress between two adjacent layers is proportional to the velocity gradient in a direction perpendicular to the layers:THE HYDRAULICS OF OPEN CHANNEL FLOW

where is the shear stress between adjacent fluid layers, is the dynamic viscosity of the fluid, V is the velocity and y is the direction perpendicular to the fluid motion. Fluids that obey Newton’s law of viscosity are called Newtonian fluids.THE HYDRAULICS OF OPEN CHANNEL FLOW