CE360 Final Exam SG
T/F: Reynolds number is the ratio of inertial force to gravity force
False
When a fluid is said to "deform continuously under the action of shearing stress", this means that: a. the fluid changes shape as long as the shearing stress is applied b. the fluid will return to the original shape once the shearing stress is removed c. the fluid will fill the container into which it is placed d. the pressure in the fluid will vary with depth in the fluid
A.
Pressure measured relative to absolute zero, only occurs within a vacuum
Absolute Pressure
a unique property of open-channel flows is that their surface can deform and form waves
Froude Definition
What are the following? - Resultant Forces: lift and drag - Boundary Layer Formation - Transition from Laminar to Turbulent Flow
3 Characteristics of Flow Over Immersed Bodies
Which of these terms is not included in conservation of mass? A. Mass entering the control volume B. Net momentum due to mass (Out-In) acting on the control volume C. Time rate of change of the mass in the control volume D. Mass leaving the control volume
B
what is a pathline a. a distance along a streakline b. the line traced out by a given particle over time c. pathline is just another term for streakline
B
Distance from the plate at which the fluid velocity is within some arbitrary value of the upstream velocity
Boundary Layer Thickness
if an equation involving "k" variables is dimensionally homogeneous, it can be reduced to an relationship among "k-r" independent dimensionless products, where r is the minimum number of reference dimensions required to describe the variables
Buckingham Pi Theorem
tells us how many dimensionless products are required to replace the original list of variables (Qualitative description of the physical properties)
Buckingham Pi Theorem
As a stagnation point, all of the following are true except a. flow velocity at the point is 0 b. kinetic energy turns into pressure energy c. cavitation will likely occur at stagnation point d. the difference between stagnation pressure and static pressure can be used to measure velocity
C
for an inclined plane surface submerged in static fluid, select the correct statement from below: A. the pressure acting on the plane is constant everywhere B. the center of pressure is at the centroid of the plane surface C. the resultant pressure force is perpendicular to the surface D. none of the above
C
what is a streakline a. lines perpendicular to the velocity field b. a phenomena caused by unsteady flow c. all the particles in a flow that have previously passed through a common point
C
"piezometric head line" and it represents the sum of the pressure head and elevation head
Hydraulic Grade Line
As a rule of thumb, typical external flows with Reynolds numbers greater than 100 are dominated by what?
Inertial Effects
a function of pipe diameter and rounding of the entrance. Note that a significant reduction in this can be achieved with only slight rounding
KL
Corresponding velocity ratios (Vm/Vp) and acceleration ratios (Am/Ap) are constant in the flow
Kinematic Similarity
hydrostatic pressure exerts a force that is __________________ to a planar surface
NORMAL
The flat plate drag coefficient is a function of relative roughness and ________________________
Reynolds number
The velocity of the rotating body is given by the product of distance from rotation axis and _______________
Rotational speed of shaft
What are the following requirements for? 1. All of the corresponding pi terms must be equated between the model and the system 2. The predictor equation must have the same function for the model and the prototype
Similarity
When measurements made in the laboratory can be used to develop models of the real system based on a scaled experimentation design it is known as:
Similitude
T/F: Streamline coordinates in 2-D form consistent component along the streamline s and the perpendicular to the streamline n
T
Newtonian Fluid Equation
T= C du/dy
For water flowing in a pipe, when the inflow and outflow velocities are not uniform across the cross sectional area:
The continuity equation can still be used by estimating an average velocity
simple open air configuration and differential configuration has a higher specific weight than the fluid in the container (gauge fluid), has the ability to measure the pressure in a gas
U-tube manometers
what does a negative gage pressure mean
a vaccum pressure exists in the measured fluid
what is used to find the relationship of atmospheric pressure
barometer
losses are due to a separation region of flow near the inside of the bend (type of minor loss)
bends in pipes
a thin _________________ results next to the plate where velocity transitions from u=U to u=0 on the plate
boundary layer
fixed and non-deforming volume used to facilitate the application of Newtons 2nd Law
control volume
for confined flows, increases in velocity result in _______________ in pressure, which could lead to _______________
decreases; cavitation
what is our version of the ideal gas law
density = P/RT
specific gravity = ?
density of fluid/ density of water at 4 degrees Celsius
specific weight (gamma) = ?
density*gravity
a fundamental difference between laminar and turbulent pipe flow is that the shear stress which causes turbulent flow is a function of fluid ____________ and the pipe _______________ characteristics
density; surface
when a surface is submerged within a fluid, the fluid exerts forces on the surface which vary with the __________ and _______________ of a system
depth and geometry
formal approach for determining which system properties should be included in a laboratory model and how they can be related
dimensional analysis
the practice of reducing the complexity of an experimental program, & at the same time helping us increase the ability to use this experiment information
dimensional analysis
dimensions on both sides of the equation are equal
dimensional homogeneity
the resultant force in the direction of fluid
drag force
represents the potential energy of a fluid particle in terms of its height from reference datum z
elevation head
we can analyze the energy of open-channel systems using the _________________________ _________________________
energy equation
represents the total head obtained using piezometers and pilot tubes
energy line
the region of flow where the fluid enters the pipe
entrance region
T/F: For complicated problems it is often less feasible to use models to predict specific characteristics of the system than to develop general correlations
false
T/F: For fully submerged object, it is stable when the objects center of gravity is higher than the center of buoyancy
false
T/F: Geometric similarity requires the ratio of forces in the model and the prototype system to be the same
false
T/F: Momentum equation is a scalar equation
false
T/F: Moving along a manometer, the pressure increases when you go up
false
T/F: Shear stress always varies linearly with shear strain rate
false
T/F: The lines that are tangent to the velocity vectors throughout the flow field are called steady flow lines
false
T/F: kinematic viscosity is defined as the ratio of the absolute viscosity to the fluid mass
false
the required number of pi terms is what compared to the number of original variables?
fewer than
stagnation points exists for any stationary body placed in a _________________ ____________
flowing fluid
pressure = ?
force/area
head loss can be depicted graphically as the _______________ ____________
friction slope (Sf)
location where the velocity profile is the same as any cross sectional area of the pipe in that our velocity is not changing with respect to x
fully developed flow
Name three types of similarity that must be satisfied to say that a model and a system have "complete similarity"
geometric, dynamic and kinematic similarity
type of non-uniform flow: - flow depth changes slowly with distance (dy/dx << 1)
gradually varying flow (dy/dx <<1)
a piezometer is only suitable if the pressure in the container is ________________ than atmospheric pressure and the p is relatively _____________
greater; small
total system losses = ? ____ = major losses + minor losses
hL
The Bernoulli equation can be written in terms of heights called what?
heads
pressure changes only with respect to _______________
height
used for measuring small pressure differences
inclined tube manomers
when is the specific weight (gamma) is constant
incompressibility of fluids
In the equation for viscosities v=u/p, v denotes the ______________ viscosity a. absolute b. dynamic c. kinematic d. shear stress
kinematic
velocity in an alternative form defined with a fluid's density
kinematic velocity
the resultant force normal to the upstream fluid
lift force
pressure varies _____________ with depth in a uniform static fluid
linearly
the most difficult step in the method of repeating variables is ___________________?
listing all of the variables that are involved in the problem
density = ?
mass/volume gamma/gravity
the sum of the pressure, velocity head and elevation head is constant along a streamline all while ASSUMING NO FRICTION OR OTHER ENERGY LOSSES
meaning of Bernoulli's equation
Most real world pipe systems consist of more than straight pipes. Additional components (valves, bends, tees, etc.) add to the overall head loss of the system. What are these losses called?
minor losses
if the pipe lies above the hydraulic grade line, then the pressure within the pipe is?
negative (atmospheric)
What is the SI unit for Force is a. Pounds per Square inch b. Newtons c. Pascals d. kg per square meter
newtons
To derive the Bernoulli equation, we integrated a conservation law (equation) along a streamline between two points. This conservation law is: a. conservation of mass b. conservation of energy c. Newton's second law F=ma d. none of the above
newtons second law
a nonzero fluid viscosity will result in a ________________________________ where fluid sticks to the solid
no slip boundary
depth varies with distance (dy/dx does not equal zero)
non-uniform flow
T/F: The second similarity requirement indicates that the model and the system must be operated at the same Reynolds number
True
if the tank nozzle is _______ smooth and well contoured, the jet diameter is _________ than the hole diameter
not;less
what forces act upon a fluid of no shearing stresses are present
only pressure and weight
time rate of change of the position of a particle vector V
particle velocity
the line traced out by a given particle over time
pathline
Fr acts _____________________ to an inclined surface
perpendicular
the fluid velocity seen by an observer moving with the control volume
relative velocity, W
a negative gauge pressure is also known as a ____________ pressure a. vapor b. vacuum c. relative d. hydrostatic
vacuum
a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways (type of minor loss)
valves
In a moving fluid, the distance between the energy line (EL) and the hydraulic grade line (HGL) is a. velocity head b. pressure head c. potential head d. dynamic pressure
velocity head
In the Bernoulli equation, the term v^2/2g denotes: a. velocity b. pressure head c. velocity head d. position head
velocity head
represents the vertical distance needed for the fluid to fall freely to reach velocity v from rest
velocity head
what does Hc stand for in the resultant force equation for an inclined surface
vertical distance from the fluid surface to the centroid of the area
In the derivation of Bernoulli equation, what is assumed to be negligible? a. pressure effects b. steamlines c. viscous effects d. temperature effects
viscous effects
Flow past an object can be treated as a combination of _____________________ in the boundary layer and ____________________________ elsewhere (Large Re number)
viscous flow; inviscid flow
What is the resultant force due to in reference to lift and drag concepts?
viscous resistance and fluid pressure
when does cavitation occur?
when the fluid pressure approaches its vapor pressure
when do we use manometers
where pressure measurements are required
what are the 4 assumptions used to derive Bernoulli's equation
1. steady flow 2. contact density 3. shearing forces not included 4. integrated along the streamline
specific volume = ?
1/p "inverse of density"
Requires the ratio of forces in model and the system to be the same: achieved by equating important dimensionless groups
Dynamic Similarity
streamlines are lines that are ___________ to the _________ vectors through the flow field
tangent; velocity
streamlines are lines that are ______________ to the _________________ vectors through the flow field
tangent; velocity
In the moment-of-momentum equation Vtheta is the _______________________________ component of absolute velocity
tangential
what function of the upstream flow dictates the depth ratio across a hydraulic jump
the Froude number
what does Yc stand for in the resultant force equation for an inclined surface
the distance on the y-axis to the centroid
what does it mean if Specific Gravity is less than 1
the fluid is lighter than water
Cavitation occurs when: a. the flow becomes unsteady b. the fluid velocities approach zero c. the fluid pressure approaches below its vapor pressure d. fluid is discharged into the atmosphere
the fluid pressure approaches below its vapor pressure
two identical circular plates are submerged in a tank. One lying flat against the bottom of the tank and the other standing vertically against the left wall. Which plate has a larger resultant force exerted on the plate by the water in the tank?
the horizontal plate
In the Linear Momentum Equation, the sum of forces acting on the control volume is equal to ____________
the net rate of linear momentum flow through the control surface
what multiple pipe system does this describe: - significantly more challenging - must determine flowrates into or out of reservoirs - must determine flowrate directions
three reservoir problem
T/F: A floating body is said to be stable if when displaced the body returns to equilibrium
true
T/F: The Bernoulli equation is valid for steady, incompressible flow with negligible viscosity effect
true
T/F: To apply F=ma normal to the streamlines, the normal components of force are needed
true
T/F: Under Bernoullis assumptions, the Energy Grade Line is always horizontal
true
T/F: nonwetting liquid in a small tube will form a depression due to capillary action
true
T/F: the linear momentum equation for an inertial control volume is a vector equation
true
T/F: the pressure drop per unit length that develops due to friction cannot generally be solved analytically
true
T/F: the term in the material derivative given as d()/dpi is zero for steady flow
true
usually for open channel flow, the flow is ___________________
turbulent
- Structure is complex, random and irregular - the velocity at any location is unsteady in a random fashion - shear stress is much larger than in laminar boundary layer flow
turbulent flow
what is the primary cause of the head loss that occurs across a hydraulic jump
turbulent mixing
depth of flow does not vary along channel (dy/dx = 0) where y is depth of flow and x is distance along the channel
uniform flow
what are the steps for hydrostatic force on an inclined surface
1. find resultant force (Fr) 2. Location (Yr & Xo) 3. Moment (Io)
for a body partially submerged in a fluid at equilibrium, which of the following is true a. the weight of the body is equal to the weight of the volume of fluid displaced b. the weight of the body is less than the weight of the volume of fluid displaced i dont feel like typing the other choice so you have a 50/50 chance
A
what is the material derivative used for? a. to describe time rates of change for a given particle b. To describe the rime rates of change for a given flow c. To give the velocity and acceleration of the flow
A
when fluid flow is characterized as fully turbulent, which of the following is a true statement? a. friction factor will increase with increase of Re number b. friction factor will decrease with increase of Re number c. friction factor is independent of Re d. friction factor is independent of relative roughness
C
for a plane surface horizontally submerged in static fluid, select the incorrect statement from below: A. the pressure acting on the plane is constant everywhere B. the center of pressure is at the centroid of the plane surface C. the resultant pressure force is perpendicular to the surface D. the pressure force magnitude does not depend on the distance between the plane and free surface
D
specific gravity is the ratio of: a. density of the fluid to density of water at 4 degrees Celsius b. specific weight of the fluid to specific weight of water at 4 degrees Celsius c. actual gravity to standard gravity d. Both (a) and (b)
D
which of the following is NOT correct a. a streamline is a line that everywhere is tangent to the velocity field b. a streak line consists of fluid particles in a flow that have previously passed through a common point c. a path line is a line traced out by a given particle, i.e., it is the particle's trajectory d. for unsteady flow, all above three lines are the same
D
equation used for computing frictional (or major losses) for any dully developed, steady, incompressible flow
Darcy-Weisbach Equation
What is the formal approach for determining which system properties should be included in a laboratory model and how they can be related called?
Dimensional Analysis
the dimensions of surface tension are
F/L
pressure measured relative to atmospheric pressure
Gauge pressure
model must be a scaled version of the system including the finest features of the system, such as surface roughness, that may significantly influence flow: achieved by accounting for important lengths and materials
Geometric Similarity
fluid cannot turn sharply at the outlet
Vena Contracta
The boundary layer thickness is defined in terms of what kind of flowrate?
Volumetric
The only possible dimensionless groups which combines velocity (V), length (L), and time t is a. VL/t b. VL/t^2 c. Vt/L d. Lt/V
Vt/L
simple manometer utilizing a single static and homogenous fluid; we have a fluid with specific weight and height, and the tube is open to the atmosphere
piezometers
what multiple pipe system does this describe: - a fluid particle traveling from reservoir A to reservoir B can take any available path - Governing Eqns: Qtotal = Q1 + Q2 + Q3 hL1 = hL2 = hL3
pipes in parallel
What multiple pipe system does this describe: - every fluid particle passes through each pipe - the flowrate is the same in each pipe - head loss from A to B
pipes in series
Regarding the energy equation or the extended Bernoulli equation, by convention if a pump is in the control volume then the pump head is considered a. negligible b. positive c. negative d. frictionless
positive
The torque of a shaft is _______________ if in the same direction as rotational speed of the shaft
positive
if the pipe is below the hydraulic grade line, then the pressure within the pipe is?
positive (above atmospheric)
distance from the pipe to the hydraulic grade line indicates the _______________ __________ in the pipe
pressure head
represents height of a column of fluid to produce pressure
pressure head
what is NOT true about a stagnation point a. velocity is zero b. pressure is zero c. occurs on any stationary body placed into a flowing fluid d. a Pitot tube takes advantage of this phenomenon
pressure is zero
The location of the resultant force is at centroid of __________________ ________________
pressure prisms
under laminar flow conditions, the pressure drop per unit length at a given flow rate, Q, is:
proportional to D^-4
type of non-uniform flow: - flow depth changes significantly more rapid with distance (dy/dx about 1)
rapidly varying flow (RVF)
Increasing Re results in boundary layer __________________
separation
the point in which the fluid inertia becomes more important so that it can no longer follow the curved path around the object
separation location
relate lab results to our real setting; measurements made in the laboratory can be used to develop models of the real system based on a scaled experimentation design (usually smaller than the real system)
similitude
Inclined tube manometers are ideal for measuring?
small pressure differences
As the Reynolds number increases, the region ahead of the cylinder in which the viscous effects are important becomes:
smaller
a hydrometer is used to measure A. temperature B. specific gravity C. viscosity D. surface tension
specific gravity
the ratio of the density of a fluid to the density of water
specific gravity
for most fluids, we assume incompressibility, which means that ______________ ______________ is constant
specific weight
no changes with respect to time at a given position in the flow field
steady flow
Three assumptions of the Bernoulli's Equation are _______________ a. steady, incompressible, and inviscid flow b. unsteady, incompressible, and inviscid flow c. steady, incompressible, and viscous flow d. steadty, compressible, and inviscid flow
steady, incompressible and inviscid flow
all particles in a flow that have previously passed through a common point IN STEADY STATE
streakline
a line that is everywhere tangent to the velocity field
streamline
lines tangent to the velocity vectors at every point
streamlines
losses due to a sudden contraction or expansion in pipe diameter are a function of the area ratio
sudden contraction or expansion (type of minor loss)
the intensity of molecular attraction per unit length of interfacial contact
surface tension
