Theory-based Quiz

Basics of Fluid Dynamics ITC

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1 / 44

In the case of Couette flow between two moving plates, the distribution of shear stress inside the fluid is:

Linear

Constant

Parabolic

Cubic

2 / 44

A massless particle in an unsteady flow is tracked from an initial position at ($x_0$,$y_0$,$z_0$) at $t=t_0$ to a second position at ($x_1$,$y_1$,$z_1$) at $t=t_1$. The curve traced out by the particle is referred to as a ________.

Timeline

Streamline

Streakline

Pathline

3 / 44

We wish to use CFD to model the air flow around a car. The car is travelling north at a speed of $60$ $mph$. The wind is blowing south with wind speeds of $10$ $mph$. What inlet boundary velocity value should be used?

50 $mph$

10 $mph$

70 $mph$

60 $mph$

4 / 44

Brinkman Number is defined as the ratio of

Heat exchanged by convection and that generated by viscous dissipation

Heat exchanged by conduction and convection

Heat generated by viscous dissipation and that exchanged by conduction

Thermal diffusion and momentum diffusion

5 / 44

Which of the following flow visualization technique is useful for observing shock waves in supersonic flows?

Schlieren photography

Smoke lines

Surface 'Oil Flow'

Tufts

6 / 44

Which of the following statements are true regarding the "specific gravity"?

(Select the two correct answers.)

It is the ratio of density of the material to the density of mercury.

When the specific gravity of an object is less than $1$, the object will float in water.

When the specific gravity of an object is less than $1$, the object will sink in water.

It is the ratio of density of the material to the density of water.

7 / 44

When a force is applied to both a solid and fluid, which of the following is true?

The fluid deforms by a fixed amount and the solid continues deforming

The solid deforms by a fixed amount but the fluid continues deforming

Both solid and fluid deform by a fixed amount

Both solid and fluid continuously deform

8 / 44

What is the expression of the pressure force component of surface forces in terms of surface integrals?

$F=-\iint ApndA$

$F=\iiint\mathrm{\Omega\nabla}\bullet\bar{\bar{\tau}} d\mathrm{\Omega}$

$F=-\iiint\mathrm{\Omega\nabla p} d\mathrm{\Omega}$

$F=\iint A\bar{\bar{\tau}}\bullet n dA$

9 / 44

Consider the barometer shown in the picture. In order to maintain the same height $h$ for the same atmospheric pressure, on a planet with twice the gravitational acceleration, we could:

Use a fluid with twice the density of the original one.

Use a fluid with $\left(\frac{1}{4}\right)^{th}$ the density of the original one.

Use a fluid with half the density of the original one.

Use a fluid with $4$ times the density of the original one.

10 / 44

Consider the manometer shown in the picture. The pressure difference $\Delta p$ is equal to:

$\rho g (h_2-h_1)$

$\rho g h_2$

$\rho g h_1$

$\rho g (h_2+h_1)$

11 / 44

For a potential flow past a circular cylinder, which of the following conditions is referred to as the D'Alembert's paradox?

Drag is zero

Velocity reaches maximum at the front and rear of the cylinder

The pressure force on the cylinder is independent of the location on the surface of the cylidner

Pressure reaches maximum at the top and bottom of the cylinder

12 / 44

The peak of Mount Everest is at an altitude of $8.84$ $km$ above sea level. To reach the summit, climbers trek through the Everest base camp, which is at an altitude of $5.4$ $km$ above the sea level. Assuming an isothermal atmosphere (temperature, $T$), what is the ratio of atmospheric pressures at the summit to that of the base camp.

$e^{\frac{-142400g}{RT}}$

$e^{\frac{-3440g}{RT}}$

$e^{\frac{-8840g}{RT}}$

$e^{\frac{-5400g}{RT}}$

13 / 44

An american football is flying horizontally in air. The plot shows the pressure contours of the ball moving from right to left. Which region has the lowest pressure?

$2$

$3$

$1$

$4$

14 / 44

In the case of 2D Poiseuille flow in a 2D planar channel, the maximum velocity occurs at:

$h/3$ from the bottom wall if gravity is acting downwards

The channel center ($h/2$ from the walls, where h is the distance between the two walls)

The walls of the channel

The channel quarters ($h/4$ from the walls, where h is the distance between the two walls)

15 / 44

A system can be considered as an open system when :

(Select the three correct answers.)

Mass coming into the system is exactly equal to the mass leaving the system

Mass coming into the system is greater than the mass leaving the system

Mass coming into the system is less than the mass leaving the system

No mass transfer between the system and its surrounding

16 / 44

The fundamental physical dimensions used in fluid dynamics are:

(Select the three correct answers.)

$V$

$L$

$T$

$M$

17 / 44

What is a reasonable simplifying modeling assumption for air at standard temperature and pressure flowing over a uniform wing section of an aircraft?

The fluid is non-newtonian

The flow is 3D

The flow is axisymmetric

The flow is 2D

18 / 44

When a fluid is at rest, the total gravitational force exerts a ________ force on any surrounding surfaces as a result of _____________.

Pressure, Newton's III law

Body, Newton's III law

Body, Newton's II law

Pressure, Newton's II law

19 / 44

Fluid statics can be used for ______

Analyzing the water flow around a boat

Studying the water flowing through pipes

Calculating the pressure exerted by water on the walls of a water tower reservoir

Calculating the drag acting on a car

20 / 44

Consider steady laminar axisymmetric flow of a viscous fluid between two long concentric cylinders where the inner cylinder of radius $R_{i}$ is stationary while the outer cylinder of radius $R_{o}$ moves about the axis at $U$. Assuming the viscosity of the fluid to be $\mu$, the velocity can be expressed as:

$u(r) = U \frac{ln(\mu/U)}{ln(R_{o}/R_{i})}$

$u(r) = U \frac{ln(r/R_{i})}{ln(R_{o}/R_{i})} $

$u(r) = \mu \frac{ln(r/R_{i})}{ln(R_{o}/R_{i})}$

$u(r) = R \frac{ln(r/U)}{ln(R_{o}/R_{i})}$

21 / 44

What are two reasonable simplifying modeling assumptions for a laminar jet flow from a circular nozzle?

(Select the two correct answers.)

The flow is axisymmetric

The flow is steady-state

The flow is inviscid

The flow is 3D

22 / 44

What is the correct value of Poiseuille number for laminar flows in round pipes?

$16$

$32$

$128$

$64$

23 / 44

What is the missing factor (?) in the non-dimensional form of the incompressible x-momentum equation? Equation is below:

$\rho^\ast\left[\frac{\partial u^\ast}{\partial t^\ast}+\mathrm{\nabla}\bullet\left({\vec{V}}^\ast u^\ast\right)\right]=-\frac{\partial p^\ast}{\partial x^\ast}+{(?)\mathrm{\nabla}}^2u^\ast$

$\frac{1}{Re}$

$Pr*Re$

$\frac{1}{Re*Pr}$

$Re$

24 / 44

In a pitot tube mounted on an aircraft, what is the difference between the total and static pressures inside the total pressure tube?

The total pressure is higher than the static pressure

They are the same

The static pressure is higher than the total pressure

The difference depends on the velocity of the aircraft

25 / 44

Consider an aircraft flying horizontally at an altitude of $8\ km$ with a speed of $250\ m/s$. The drag force is ______ with respect to the direction of motion of the aircraft.

In the same direction

In the opposite direction

Perpendicular

At an angle of $60$ degrees

26 / 44

The maximum velocity in an axisymmetric fully developed flow in a round pipe (radius = $R$) (Axisymmetric Hagen-Poiseuille Flow) occurs at ($r$= radial distance from the centerline):

$R/3$ from the bottom wall if gravity is acting downwards

The pipe centerline ($r = 0$)

The walls of the pipe

The pipe quarter ($r = R/2$ from the walls, where h is the distance between the two walls)

27 / 44

In a vertical circular water pipe $3\ m$ long with constant diameter ($D = 1\ cm$), water is flowing from inlet (bottom) to outlet (top), in a direction opposite to the gravitational force. The static pressure at the inlet is $101\ kPa$ and inlet velocity is $0.001\ m/s$. Assuming water as an incompressible fluid, the static pressure at the outlet:

Will be higher than the inlet static pressure

Will be lower than the inlet static pressure

Cannot be predicted because of insufficient information

Will be the same as the inlet static pressure

28 / 44

Which of the following statements are true in the context of an aircraft stall?

(Select the two correct answers.)

An aircraft can never stall

Stall is caused by flow separation on the airfoil

There is a sudden drop in the drag force experienced by the aircraft

There is a sudden loss of lift experienced by the aircraft

29 / 44

Which of the following statements are true about the operation of the venturi tube :

(Select the two correct answers.)

Flow rate is measured using Bernoulli's principle

Flow rate is measured from pressure difference

Temperature is measured from flow rate

Flow rate is measured from temperature difference

30 / 44

What does the Reynolds Number physically represent?

Ratio of inertial to viscous forces

Ratio of viscous to buoyancy forces

Ratio of surface tension to viscous forces

Ratio of bouyancy to inertial forces

31 / 44

The definition of an incompressible flow is: a fluid flow that always has a constant ________ .

Temperature

Density

Velocity

Pressure

32 / 44

An airplane is traveling at a Mach Number = $2$. This means the airplane is traveling at the speed which is _______ times the local speed of sound.

$4$

$0.5$

$2$

$0.25$

33 / 44

Which of the following is true when the velocity is a function of time?

Streamlines and streaklines will be same but the pathlines will be different

Pathlines, streaklines, and streamlines will not be the same.

All three, pathlines, streaklines and streamlines will be same.

Pathlines, streaklines will be same but the streamlines will be different

34 / 44

Which of the following are examples for external flows?

(Select the two correct answers.)

Blood flowing through veins

Water flowing around a submarine

Air flow over a car

Water flowing through a pipe

35 / 44

In which of the following examples is it important to consider gravitational forces acting on the fluid?

Estimating the mass flow rate of water through an horizontal pipe

Calculating the trust generated by air passing through a nozzle

Calculating the water temperature at the sink faucet exit

Analyzing the pressure that water exterts on a dam

36 / 44

What is the integral form of the body force due to the gravitational acceleration?

$F=\iint{A \bar{\bar{\tau}}\bullet n dA}$

$F=-\iiint\mathrm{\Omega\nabla p d\mathrm{\Omega}}$

$F=\iiint\Omega\nabla\bullet \bar{\bar{\tau}} d\mathrm{\Omega}$

$F=\iiint\mathrm{\Omega\rho g d\mathrm{\Omega}}$

37 / 44

Which of the following equations represents the conversation of mass equation under the incompressible flow assumption?

$P=\rho RT$

$\nabla \bullet v=0$

Momentum equation

Energy equation

38 / 44

What’s an example of a solid behaving like a fluid?

A rolling bowling ball

Sand flowing between fingers

Flowing milk

Toothpaste

39 / 44

In the case of Couette flow between two moving plates, the velocity profile is:

Linear

Cubic

Parabolic

Sinusoidal

40 / 44

The mean velocity for an axisymmetric fully developed flow in a round pipe (Axisymmetric Hagen-Poiseuille Flow) is:

Equal to the velocity at the pipe centerline

One-fourth of the velocity at the pipe centerline

Half of the velocity at the pipe centerline

One-third of the velocity at the pipe centerline

41 / 44

Which of the following terms represent the unsteady, time varying behavior of the conversation of mass equation?

$\frac{d(\rho u)}{dx}$

$\frac{d(\rho w)}{dz}$

$\frac{d(\rho v)}{dy}$

$\frac{d \rho}{dt}$

42 / 44

On this symmetric airfoil with $0$ angle of attack, where is the point of highest pressure located? Please see the image below as reference.

$3$

$2$

$1$

$4$

43 / 44

The phase of a substance depends on :

(Select the three correct answers.)

Viscosity

Temperature

Density

Pressure

44 / 44

The sensor connected to the pitot tube on a racing car is sending a record of increasing total pressure values, while the static pressure is constant. This means that the car is

Not moving

Accelerating

Braking

Keeping a constant speed

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Private: Basics of Fluid Dynamics

Total time - 60 mins.

Total number of Questions - 45