Uniform flow and Flow regimes Flashcards
Bed slope (i) = ?
Flow area= ?
i = sin(theta) = /\Z / /\L
A = (b + mh) * h
Wetted perimeter = ?
Hydraulic radius
X = b + 2h* sqrt( 1 + m^2)
R = A / X
What does R equal when it’s a shallow and wide channel?
R = h
What is the equations for uniform flow discharge?
Q = 1/n * R^2/3 * i^1/2 * A
What are the 3 ways of calculating flow discharge?
- Simple
- Trial and error
- Graphical. (plot know point the draw a best fit and use that).
How should you design flow velocity?
Flow should be less than the scour velocity so that the channel bed isn’t eroded.
Flow should be larger than deposit velocity to avoid weed production.
How do you calculate optimum b/h ratio?
What is this for a rectangle?
b/h = 2 * ( sqrt(1 + m^2) - m ) b/h = 2
How to calculate discharge in a complex channel cross section?
Split the section into more simple sections and then calculate q for each section.. Don’t include wetted perimeter for the inside edge.
Add all flow rates together to get overall discharge.
What are the two types of Non-uniform flow?
- Gradually varied flows.
2. Rapidly varied flows
Whats does disturbance wave celerity equal?
rectangle Vw = sqrt( gh )
Any shape Vw =sqrt( g * A/B )
How is the Froude number calculated and what does its value mean?
Fr = V / sqrt( g*h )
Fr < 1 - Subcritical
Fr = 1 - Critical
Fr > 1 - Supercritical
How are total and specific energy calculated?
E = Zo + hCos(theta) + V^2/2*g
Es = h + V^2 / 2*g
How do you calculate the critical flow depth?
For rectangle:
h^3 = Q^2 / (b^2 * g)
or h^3 = q^2 / g (q = Q/b)
For trapizoid: Q^2 / g = Ac^3 / Bc Ac = (b + m*hc) * hc Bc = b + 2*m*hc Trial and error
What is a hydraulic drop or jump?
Hydraulic drop: flow goes from subcritical to super critical
Hydraulic jump: flow goes from supercritical to subcritical
