Engineering Hydraulics Flashcards
What is viscosity?
A fluids resistance to deformation (flow) due to shear stresses.
Re number for open channel laminar flow?
<2000
Re number for open channel transitional flow?
2000<Re<4000
Re number for open channel turbulent flow?
> 4000
Froude number = 0
No flow
Froude number < 1
Subcritical flow
Froude number = 1
Critical flow
Froude number > 1
Supercritical flow
Definition of uniform flow?
Flow variables (velocity and depth) are constant in space
Definition of non-uniform flow?
Flow variables (velocity and depth) change in space
Definition of steady flow?
Flow variables (velocity and depth) at a given point do not change with time (constant flow rate)
Definition of unsteady flow?
Flow variables (velocity and depth) at a given point change with time (increase/decrease of flow rate)
Hydraulic radius = ?
R = A/P (area/wetted perimeter)
In infintely wide channels what doesnt affect flow?
Walls/banks of channel
How wide does a channel have to be to ignore effects of walls/banks?
10X its flow depth
How do you obtain flow depth from the Manning’s equation?
Trial and error using iterative method
Weak Hydraulic Jump
1.7<Fr<2.5
Oscillating Hydraulic Jump
2.5<Fr<4.5
Steady Hydraulic Jump
4.5<Fr<9
Strong Hydraulic Jump
Fr>9
What are the conditions for gradually varied flow?
Gradual variations in flow depth and velocity
No surface discontinuities
Component of weight does not balance friction
Geometric slope different from friction slope
Mild slope conditions
S<Sc
yn>yc
Steep slope conditions
S>Sc
yc>yn
Critical slope conditions
S=Sc
yc=yn
Horizontal slope conditions
S=0
yn -> infinity
Adverse slope conditions
flow depth is critical
Driving forces in pipe flow?
Pressure (& sometimes gravity)
Reynolds number represents?
Ratio of inertial force to viscous force
Re number for pipe laminar flow?
<2300
Re number for pipe transitional flow?
2300<Re<4000
Re for pipe turbulent flow?
> 4000
How is turbulent flow charecterised?
Irregular, random, chaotic
What equation is used to evaluate head loss in turbulent pipe flow?
Darcy-Weisbach euation
What do you use to get pipe friction factor for turbulent flow? (lamda)
Moody diargam
How do you get mean flow velocity?
U=Q/A