Part 5: Flow in Pipes and Pipe Networks Flashcards
A ____________ flow (or flow field) is a flow for which the fluid is contained within the boundaries of a body.
Internal. An example of this is a duct, river Channel, or valve
T or F: movement of fluid is in response to a pressure gradient?
True
T or F: movement of fluid is in response to a gravity?
False, It is a response to pressure gradient
T or F: Open channel flow in liquids is in response to gravity?
True
T or F: Open channel flow in liquids is in response to a pressure gradient?
False, a response to gravity
What is the Reynolds number for a laminar flow in a pipe?
Re<=2100
What is the Reynolds number for a transitional flow in a pipe?
2100<=Re<=4000
What is the Reynolds number for a turbulent flow in a pipe?
Re>=4000
T or F: The centre core of a fluid as it enters the entrance region from a tank to a pipe acts as a ________ fluid.
Inviscid
T or F: Unsteady flow through a pipe represents a balance between pressure and viscous force?
F. a steady flow represents this
At entrance into a pipe, a force imbalance results in fluid…
acceleration
Pressure differences in a horizontal pipe occur due to ___________
Shear stress resistance
T or F: A horizontal pipe experiences some head loss due to gravity?
False, only to shear stress resistance.
What is Poiseulle’s law?
Poiseulle’s law gives the discharge for laminar flow in a horizontal pipe
_____________ Law gives the discharge for laminar flow in a horizontal pipe
Poiseuille’s
T or F: For non-horizontal pipes it is not necessary to consider the effects of gravity in the pressure term?
False. It is necessary
for a constant diameter, horizontal pipe, ∆p represents the __________ of the flow in the pipe
energy loss (head loss)
Where does the head loss energy go?
internal energy, heat
T or F: For flow in a pipe, the onset of turbulence is related to the Reynolds number
True
The head loss in the ___________ equation represents the change in piezometric head over a length of pipe
Darcy-Weisbach
T or F: The head loss given by the Darcy-Weisbach equation represents the ‘minor’ head loss in a piping system
False, It represents the major
Friction factor relationship for uniform roughness represented by _________
Stanton diagram
T or F: The moody diagram is used in both steady and unsteady flow?
False, only steady
Head loss at an entrance to a pipe from a reservoir is due to all of the following except: Boundary friction (small) Gravity Flow separation Flow expansion
Gravity
Head loss at an exit from a pipe into a reservoir due to:
Flow Expansion
Abrupt expansion in a system is also called:
Borda Head Loss
T or F: For both laminar and turbulent flow in a rectangular pipe, use Darcy-Weisbach head loss equation with Dh
True
_______ head is the head required to overcome the level of difference between a pumphouse and reservoir?
Static
_______ head is the head required to overcome the energy losses in the system
Dynamic
T or F: For pipes in parallel, head loss between any two points must be the same regardless of the path taken
True
What is the NPSH(r)?
Net Positive Suction Head (required). It is the minimum value of the suction head that a particular type or design can tolerate without cavitation occurring
T or F: Since the pump has a characteristic H-Q curve and the system has a characteristic H-Q curve, the point at which the system will operate will be at the intersection of the two curves?
True
___________ is a pressure eave created when a flowing liquid is suddenly decelerated
Water Hammer
The time for the pressure wave to travel to the reservoir and back to the valve is called the _________ of valve closure
critical time
