Principles & Equations of Fluid Motion & Applications

Question 1

Give the definition for: Steady Flow

Answer 1

Parameters at any point do not change with time.

Question 2

Give the definition for: Unsteady flow

Answer 2

Parameters at any point change with time.

However, many unsteady flows may be assumed steady if average value of any quantity over a reasonable time period remains unchanged.

Question 3

What’s the difference betwee: 1.) Uniform Flow and 2.) Non-Uniform Flow

Answer 3

1. ) Parameters do not change from point to point over a specified region.
2. ) Parameters values change from one point to the next in a specified region.

Question 4

Give the definition for: Timeline

Answer 4

Indicates velocity distribution from a fixed source line.

Question 5

Give the definition for: Streamline

Answer 5

An imaginary curve in the fluid, across which, at that instant, no fluid is flowing.

Looking at a certain point on streamline, it will be in the direction of its vector.

Question 6

You can’t have fluid flow across a stream line. What is the theoretical solution to this problem and state what it is.

Answer 6

A stream-tube, which produces a cylinder like object by combinations of streamlines.

Note: Flow can only enter and leave a stream-tube at its ends.

Question 7

What’s the difference between the Lagrangian and Eulerian methods?

Answer 7

Lagrangian only looks at the velocity vector of an individual particles.

Euler looks at the region of space. (Used more.)

Question 8

The Eulerian approach comprises of a bunch of field variables. What is the name of this group of field variables?

Answer 8

Flow field.

Question 9

Describe what the continuity equation is

Answer 9

A mathematical approach to the principle of cons. of mass.

Mass is neither created or destroyed.

Question 10

Give the definition for: Bernoulli’s Equation

Answer 10

The sum of the flow of kinetic and potential energies of a fluid particle along a streamline is constant.

Therefore, KE and PE of fluid can be converted to flow energy, causing pressure to change.

Question 11

Describe what the three types of pressure are in Bernoulli’s Eqn.

Answer 11

• Static pressure, which represents the thermodynamic pressure of the fluid.
• The pressure rise when water is brought to a stop (without heat transfer [isentropically]).
• Elevation effects such as the effect of fluid weight on pressure.

Question 12

What is stagnation pressure.

Answer 12

Sum of static and dynamic pressures.

Question 13

State the three types of head and their meanings.

Answer 13

• Pressure head; height of a fluid column that produces the static pressure ‘p’.
• Velocity head; Elevation needed for a fluid to reach the velocity u during frictionless freefall.
• Elevation head represents the potential energy of the fluid.

Note: H is the total head flow

Question 14

What principle does the manometer depend on?

Answer 14

Fluid columns can be used to measure pressure differences since pressure varies with depth.

Question 15

What’s a differential manometer?

Answer 15

Measure a pressure difference.

Question 16

What’s an orifice? And in particular, what does an orifice plate measure?

Answer 16

An orifice is an aperture through which fluid passes.

An orifice plate measures the massflow rate.

Question 17

Explain the flow from a sharp edged orifice.

Answer 17

Fluid approaching the orifice converges towards it until it reaches the point ‘cc’.

The streamline then becomes parallel. This point corresponds to the minimum area and is called the vena contracta.

Question 18

What is the stagnation point?

What device uses this principle?

Answer 18

The point in a fluid where the velocity is reduced to zero.

A pitot tube uses this principle of stagnating flow, by allowing no velocity at its entrance.

Question 19

What does the Pitot-Static tube measure?

Answer 19

Tubes recording static pressure and stagnation pressure combined.

Question 20

What is the Venturimeter?

Answer 20

A flow measuring device used in pipelines.