Fluids Test 3

Some pipe flow problems require a trial and error solution technique.

True

The number of required pi terms is fixed in accordance with the pi theorem

True

The pressure drop per unit length that develops due to friction cannot generally be solved analytically

True

Variables can be classified into three general groups: geometry, material properties, and external effects

True

The dimensions of head loss can be expressed in dimensions of length (L). As such, the head loss is a measure of:

the energy loss per unit mass due to friction.

The Mach number and what other number cannot be used in the same problem?

Cauchy number

For air flow over the wing of an airplane, which of the following defs of Reynolds # will let you determine the drag force on the wing? Uo is the freestream velocity.

(UoL)/v

For air flow at a velocity Uo over a surface that has a length in the flow direction of L and a width W , which is a complete set of parameters for representing the force?

(UoL)/v, W/L, & D/(pV^2(L^2/2))

A 1/20th scale model of a wing is used to determine forces on the actual wing. The area of the scale model of the wing is

1/400th that of the actual wing

A 1/10th scale model of an airplane is tested in a wind tunnel. The Reynolds number of the model is the same as that of the full scale airplane in air. The velocity in the wind tunnel is

10 times that of the full scale airplane

What value must the Reynolds number be lower than to be considered laminar for pipe flow?

2100

Water flows steadily through a smooth pipe with a Reynolds number Re1. If the velocity is doubled the relation between the Reynolds number Re2 after the increase to Re1 is

2Re1 = Re2

For a Length scale of 1/10 and a prototype velocity of 30mph, what is the required model velocity

300 mph

What value must the Reynolds number be higher than to be considered turbulant for pipe flow?

4000

What is most likely to be the main driving force in pipe flow?

A pressure gradient

Flow can cross a streamline

False

Steady, fully developed pipe flow experiences no ______.

Acceleration

Dimensional Analysis

Allows us to apply measurements on one system to another similar system

Water flows steadily through a horizontal circular pipe. Which curve most correctly describes the pressure drop through the pipe as the length is increased.

B

How is an orifice meter constructed?

By inserting a flat plate with a hole between two flanges of pipe

How is the acceleration of a fluid particle described

By using the material derivative

Water discharges from a submerged pipe into a reservoir. What eventually happens to the kinetic energy of the flow in the pipe after the fluid enters the reservoir?

Converts to thermal energy

What term of the continuity equation, when held constant, allows the continuity equation to reduce to a relationship involving only velocity gradients for incompressible fluids?

Density

The pi terms must always be what?

Dimensionless

A scale model of submarine is used to determine the drag force on the actual submarine during deep water cruising. Which of the following are the appropriate dimensionless pi groups for this prob?

Drag coeff and Reynolds

The dimensions of the variable on the left side of the equation must be blank the dimensions of any term that stands by itself on the right side of the equal sign

Equal to

The required number of pi terms is what compared to the number of orginal variables

Fewer than

A scale model of the flow over a dam is tested in a lab and used to determine the flow rate over the actual dam. Which of the following are the appropriate dimensionless P-groups to determine the water velocity and discharge for the actual dam

Froude number

Dimensional analysis is when the results of an equation will be what in relation to the system of units chosen

Independent

For time dependent probs, which of the following is crucial for successfully finding a solution?

Initial Conditions

For a very rough pipe wall the friction factor is essentially constant at high Reynolds numbers. In this regime, as the mass flow rate increases, the pressure drop per unit length

Increases

There is a steady laminar flow of water in a pipe of length L.

Increases

The units for the stream function are

L^2T^-1

Which shear stress is dominant in the viscous sublayer?

Laminar

For large Reynolds numbers, the inertial forces are blank the viscous forces

Larger than

How do the dimples on a golf ball affect drag

Larger than

A 1/20th scale model of airplane is used to determine forces on the actual airplane. The 1/20th scale refere to the

Lengths

One set of basic dimensions is mass M, length L, and time T. For this system, the dimensions of force F are

MLT^-2

A representation of a physical system that may be used to predict the behavior of the system in some desired respect is what?

Model

Is Poisuille's law valid for transitional flow?

No, it is only valid for laminar flow.

Lines along which the stream function is constant are

Streamlines

What is a general decription of the flow rate in laminar flow?

Small

The Weber number is a relationship between the inertial force and what other force

Surface Tension

Which type of expansion series is used in the development of the mass flow rate equation

Taylor

What is the Reynolds number?

The Reynolds number is the ratio of the inertia to viscous effects in the flow.

What is another term for the viscous effects that cause a fluid to stick to the wall of a pipe?

The no-slip boundary condition

The Reynolds number can be interpreted as

The ratio of inertial to viscous forces

A 1/10th scale model of an airplane is tested in a wind tunnel at the same Reynolds number as that of the full scale airplane. The drag coeff of the model is

The same as that of the full scale airplane

What parameter of the flow is responsible for head loss?

The shear stress on the wall

Consider the following steady state laminar flow velocity distributions between two plates. Which of the following are true about the flow?

The upper plate is stationary and the lower plate is moving to the left.

For irrational flow, the vorticity is zero

True

If a dye streak injected into a flow almost immediately becomes blurred and spreads across the entire pipe, the flow is said to be ____.

Turbulent

Which results in more efficient heat exchange, laminar or turbulent flow?

Turbulent

Which has a "flatter" velocity profile?

Turbulent flow

For the laminar flow of a Newtonian fluid, the shear stress is proportional to the _____.

Velocity gradient

Which of the three meter types is the most accurate?

Venturi

The rate of change of the volume per unit volume is called the

Volumetric dilation rate

How does vorticity relate to the rotation vector

Vorticity is twice the rotation vector

What is a bellows meter usually used to measure in most households?

What is a bellows meter usually used to measure in most households?

Translation, linear deformation, rotation and angular deformation are the four types of motion that a fluid element can experience

Yes

Water is flowing in a pipe. Which is the correct statement about the effect of an increase in the Reynolds number of the flow:

if the flow is laminar it could become turbulent.

Air is flowing in a pipe. Which is the correct statement about the effect of a decrease in the Reynolds number of the flow:

if the flow is turbulent it could become laminar.

For fully-developed viscous flow in a horizontal pipe, which of the following is true:

pressure forces are balanced by shear forces.

What is another term for the viscous effects that cause a fluid to stick to the wall of a pipe

strongly dependent on whether the flow is laminar or turbulant

If the left hand side of the energy equation were larger than the right hand side:

the flow would not be possible

Water flows steadily through a smooth pipe. If the velocity is increased

the friction factor decreases

If the elevation difference H were increased,

the mass flow rate would increase.

The total head of a steady flow, H, is a measure of:

the maximum height the fluid could reach with no additional work input.

For a steady uniform flow of an incompressible liquid that enters a pipe, which of the following is true for the entrance region:

the maximum velocity increases with distance from the entrance.

The same pipe is used to carry both air and water. For the same fluid velocity and friction factor for the air and water flows:

the pressure drop for the water flow is greater than that for the air flow.

Water flows steadily through a rough pipe with the flow in the regime in which friction factor is constant. If the velocity is increased

the pressure drop over the pipe length increases

Water flows steadily through a smooth pipe of a given length. If the velocity is increased

the pressure drop over the pipe length increases.

Turbulence intensity is a measure of ______.

the size of the fluctuations of various parameters

In the case of fully developed pipe flow, _____.

the velocity profile is the same at any cross section of the pipe

The pressure drop in a pipe is greater if the flow is ______.

turbulent

The three most common devices used to measure the instantaneous flowrate in pipes are ____, ____, and ____.

venturi meter, orifice meter, nozzle meter.

For a very rough pipe wall the friction factor is constant at high Reynolds numbers. For a length L1 the pressure drop over the length is Δp1. If the length of the pipe is then doubled, what is the relation of the new pressure drop Δp2 to the original pressure drop Δp1 at the original mass flow rate?

Δp2 = 2 Δp1