Open Channel FLow Flashcards
(28 cards)
What characterizes open-channel flow?
Flow with a free surface exposed to atmospheric pressure, such as rivers and canals.
What is Manning’s equation used for?
To calculate flow in open channels: Q = (1.486/n) * A * R^(2/3) * S^(1/2).
Define the hydraulic radius in open-channel flow.
Hydraulic radius R = A / P, where A is the flow area and P is the wetted perimeter.
What is the typical range of Manning’s roughness coefficient (n)?
From 0.010 (smooth channels) to 0.035 or higher (natural streams).
What does normal depth represent in open-channel flow?
The depth of flow under uniform conditions for a given slope and discharge.
What is critical depth in open-channel flow?
The depth at which specific energy is minimized for a given discharge.
What is the Froude number used for?
To determine flow regime: Fr = V / (gD)^0.5.
What is the purpose of a plunge pool?
To dissipate energy and reduce erosion downstream of an outfall.
What is an energy dissipator?
A structure designed to reduce the energy of flowing water to prevent erosion.
Where is a drop structure commonly used?
In channels to safely convey water down steep slopes.
What happens to the hydraulic grade line after a drop structure?
It drops abruptly due to loss of elevation and energy.
What is the role of an apron in a culvert outlet?
To prevent erosion by distributing the flow energy.
What causes hydraulic jumps?
A transition from supercritical to subcritical flow, often used for energy dissipation.
What is the Rational Method equation?
Q = CiA, where Q is peak flow, C is runoff coefficient, i is rainfall intensity, A is drainage area.
What is the function of a stormwater inlet?
To collect surface runoff and convey it into a drainage system.
What is a curb inlet?
An opening along a street curb for stormwater collection.
What is the purpose of a culvert?
To allow water to pass under roads, railways, or embankments.
What governs the capacity of a gutter flow?
Street slope, cross-section geometry, and inlet spacing.
What is inlet control in culverts?
Flow is controlled by the entrance conditions of the culvert.
What is outlet control in culverts?
Flow is governed by the tailwater elevation and barrel characteristics.
How is the design storm selected for storm drain design?
Based on return period and criticality of infrastructure (e.g., 10-year or 25-year storm).
What defines subcritical flow?
Flow with Froude number < 1; dominated by gravity and slower movement.
What defines supercritical flow?
Flow with Froude number > 1; dominated by inertia and rapid movement.
How does the slope of a channel affect flow regime?
Steep slopes tend to cause supercritical flow, mild slopes cause subcritical flow.
