Week 2

Question 1

What is the pressure distribution in a static fluid dependent on?

Answer 1

The pressure distribution in a static fluid is dependent on the weight of the fluid.

Question 2

What condition is denoted by zero fluid velocity?

Answer 2

Hydrostatic condition.

Question 3

In a static fluid, what is the nature of the pressure property?

Answer 3

The pressure is a point property, independent of the orientation.

Question 4

What is the equilibrium of a fluid element determined by?

Answer 4

The sum of all per-unit-volume forces equals the mass per unit volume times the acceleration of the fluid element.

Question 5

What happens to viscous stresses and acceleration in hydrostatics?

Answer 5

Both viscous stresses and acceleration are zero.

Question 6

What does the hydrostatic distribution state about pressure variation?

Answer 6

Pressure in a uniformly distributed static fluid varies only with vertical distance and is independent of the shape of the container.

Question 7

What is the Lagrangian description?

Answer 7

Follows individual fluid element and is described as a function of time.

Question 8

What is the Eulerian description?

Answer 8

Records fluid properties at fixed positions and individual particles are not identified.

Question 9

What is the initial position of a fluid element in the Lagrangian description?

Answer 9

X vector = (X, Y, Z)

Question 10

Define the material coordinate.

Answer 10

Initial position, X

Question 11

What does the material derivative represent in fluid mechanics?

Answer 11

The material derivative represents the rate of change of a property following a fluid particle. Lagrangian description.

Question 12

What is the local acceleration in steady flow?

Answer 12

The local acceleration vanishes in steady flow. Flow is independent of time.

Question 13

What is the relationship between pressure and depth in a static fluid?

Answer 13

Pressure increases with depth in the fluid.

Question 14

True or False: In a static fluid, the pressure is the same at all points on a given horizontal plane.

Answer 14

True.

Question 15

Define pressure force.

Answer 15

Net force per unit element volume.

Question 16

What defines the acceleration field in fluid mechanics?

Answer 16

The acceleration field is represented by a = DV/Dt.

Question 17

What is the effect of gravity on a fluid element in equilibrium?

Answer 17

Gravity adds a body force to the fluid element.

Question 18

What is the significance of the pressure gradient in rigid-body motion?

Answer 18

The pressure gradient acts in the direction of gravity minus acceleration.

Question 19

What does the term ‘convective acceleration’ refer to?

Answer 19

Acceleration arising when a particle moves through regions of spatially varying velocity.

Question 20

When does convective acceleration vanish?

Answer 20

If flow is independent of space - uniform flow.

Question 21

Define uniform flow.

Answer 21

Flow is independent of space.

Question 22

What is the hydrostatic pressure distribution’s dependence on viscosity?

Answer 22

It is correct for all fluids at rest, regardless of their viscosity.

Question 23

What is convective acceleration?

Answer 23

Convective acceleration is made up of nonlinear products.

Question 24

What are the two descriptions of the velocity field?

Answer 24

Eulerian and Lagrangian Descriptions.

Question 25

What types of line patterns are used to visualize flows?

Answer 25

Streamlines, Streaklines, and Pathlines.

Question 26

Define a streamline.

Answer 26

A streamline is a line everywhere tangent to the velocity vector at a given instant.

Question 27

What is a pathline?

Answer 27

A pathline is the actual path traversed by a given fluid particle.

Question 28

What is a streakline?

Answer 28

A streakline is the locus (place) of particles that have earlier passed through a prescribed point.

Question 29

How are streamlines, pathlines, and streaklines related in steady flow?

Answer 29

They are identical in steady flow.

Question 30

What is a streamtube?

Answer 30

A streamtube is formed by a set of streamlines starting at points that form a closed loop.

Question 31

What is the significance of streamtube walls?

Answer 31

The fluid within a streamtube is confined and cannot cross the streamlines; thus, the walls may be fluid surfaces.

Question 32

How are streamlines calculated?

Answer 32

If the elemental arc length dr of a streamline is parallel to V, their respective components must be in proportion.

Question 33

What is a stagnation point?

Answer 33

A stagnation point is a point of zero velocity, occurring where u = v = w = 0.

Question 34

How do you find pathlines mathematically?

Answer 34

To find pathlines, solve given (u, v, w) as known functions of position and time, starting at an initial position (x0, y0, z0, t0).

Question 35

What is the method to find streaklines?

Answer 35

First find the pathlines of all particles released from a point at different times, then locate them at the current time.

Question 36

Fill in the blank: Streamlines are convenient to calculate mathematically, while _______ and _______ are easier to generate experimentally.

Answer 36

pathlines; streaklines.

Question 37

True or False: Streamlines, pathlines, and streaklines can be calculated independently of the velocity field.

Answer 37

False.

Question 38

List surface and body forces.

Answer 38

*Surface forces: pressure gradient, viscous stresses Body forces: gravity

Question 39

Define pressure head of the fluid.

Answer 39

Pressure/gamma

Question 40

Describe rigid body motion.

Answer 40

All particles in combined translation/rotation and no relative motion between particles.

Question 41

Which term vanishes in the linear momentum relation for rigid-body motion?

Answer 41

Viscous term