Open Channel Flows Introduction Flashcards
Why do civil engineers need to know about open channel flows?
- Flood Control - Protection from sea
- Hydraulic structures/Dam hydraulics - water storage
- Controlling water depth - Navigability of rivers and channels for ships
- Enabling transport
For flood control/storm protection what specifics must be looked into?
- How high must the barrier be?
- Force on the barrier in open and closed position?
- Flow velocities around structure?
How does the Thames Barrier work?
- Open and closed to control flow of river water
- Rotated on a drum and raised or lowered
What are applications in hydraulic structures?
- Dissipation of excess energy
- Fish pass to create required flow conditions for fish as they are sensitive
What is flow scour?
The removal of sediment or engineered materials from the bed or banks of a watercourse
What is a spillway?
A spillway part of a dam that is designed to allow water to flow freely over the dam during floods.
What is an open channel flow?
Flow with free surface which is driven along a conduit by gravity
What is a weir?
A weir is a small barrier built across a stream or river to control and raise the water level slightly on the upstream side,
essentially a small-scale dam.
What is an example of a channel flow?
- Channels
- Rivers
- Partially filled pipes
- Spillways
Why is the flow one dimensional?
Flow is one dimensional it varies with distance along the channel
What are the typical unknowns in channel flow problems?
Flow velocity U (erosion potential); water depth h; also cross-sectional area A, slope s (and roughness) required for a given discharge Q
What is the wetted perimeter?
Is the total length of the line represent the interface between the channel boundary and the fluid.
How do you calculate hydraulic mean depth?
h_m = A/w
What is the hydrualic radius?
R = A/P
- The hydraulic radius R is a measure of the efficiency of a channel flow
