Area 2 - Open Channel Flashcards
PART 4: Objective type on open channels
a conduit in which liquid flows with a free surface
open channel
a type of flow having a free surface and subjected to atmospheric pressure.
open channel flow
a type of flow confined in a closed conduit, has no free surface and exerts no direct pressure but hydraulic pressure only
pipe flow
if the depth of flow does not change or if it can be assumed to be constant during the time interval under consideration
steady flow
it is a flow that changes with time
unsteady flow
if the depth of flow is the same at every section of the channel
uniform flow
uniform flow is also referred to as _____. fundamental type of flow in open channels hydraulics
steady uniform flow
if the depth of flow changes along the length of the channel
varied or non-uniform flow
varied or non-uniform flow is also known as ______, where water runs in or out along the course of flow.
spatially varied or discontinuous flow
example of varied or non uniform flow
roadside gutters, side-channel spillways, washwater trough in filters, effluent channels around sewage-treatment tanks
specific energy equation (Froude no. = 1)
critical flow
factors that affect open channel flow
viscosity, gravity
together with gravity, they are the factor that basically affect open-channel flow
viscosity
what are the types of flow in terms of the effect of viscosity relative to inertia.
laminar, turbulent, transitional
water particles appear to move in definite, smooth paths, or streamlines; and extremely thin layers of fluid slide over adjacent layers
laminar
viscuous forces are weak relative to inertial forces; water particles move in irregular paths which are neither smooth nor fixed
turbulent
the effect of viscosity relative to inertia can be represented by the
reynold’s number
if the depth of flow is taken as the characteristic length, R < 500
laminar flow
if the depth of flow is taken as the characteristic length, R > 2000
turbulent flow
if the depth of flow is taken as the characteristic length, 500 < R > 2000
transitional flow
Its effect on the state is represented by a ratio of inertial forces to gravity forces, given by Froude number
gravity
the value of F, if the the flow is critical
F = 1
the value of F, if the flow is supercritical (inertial force is dominant; the flow is rapid, has high velocity, and has torrential shooting)
F > 1
the value of F, if the flow is subcritical (gravity force is more pronounced; the flow is tranquil, has low velocity, and is streamlined)
F < 1
a kind of open channel that includes all watercourses that exist naturally on the earth. eg. underground stream, rivulets
natural
a kind of open channel that is constructed or developed by human. eg. flumes, power canals, chutes, spillways
artificial
usually a long and mild-sloped channel built in the ground which may be lined or unlined
canal
it is a channel made of wood, metel, or concrete supportedabove the surface of the ground to carry water across a depression
flume
a channel having a steep slope
chute
a covered channel of comparatively short length installed to drain water trough a highway and railroad embnkments
culvert
comparatively long covered channel used to carry water through a hill or any obstruction on the ground
open-channel tunnel
according to channel geometry
prismatic and non-prismatic channel
it is the vertical distance of the lowest point of a channel section from the free surface
depth of flow
it is the width of channel section at the free surface
top width (T)
it is the cross-sectional area of the flow normal to the direction of flow
water area (A)
the length of the line of intersection of the channel wetted surface with a cross-sectional plane normal to the direction of flow
wetted perimeter
ratio of water to its wetted perimeter
hydraulic radius
ratio of water area to the top width
hydraulic depth
ratio of the dry weight of soil particles to the weight of an equal volume of water
real specific gravity
the moisture content of the soil when the gravitational water has been removed
field capacity
these are pipelines built on or near the ground surface that convey water across wide depressions
inverted siphons
subsurface drain system wherein laterals join the submain on both sides alternately
herringbone
it is the ratio of the volume of voids to the total volume of soil
porosity
it is the water retained about individual soil particles by molecular action and can be removed only by heating
hygroscopic water
it refers to the composite parts of the irrigation system that divert water from natural bodies of water such as rivers, streams, and lakes
headworks
