Chapter 4 Flashcards
What does a field representation of a fluid flow provide?
The field representation provides information on the flow’s parameters such as temperature, pressure, or velocity/acceleration as a function of spatial coordinates as well as time.
Ref: Pg 112
What are the three components of the velocity vector?
u, v, and w
Ref: Pg 113
Give the equation for the speed of the fluid.
abs(V) = (u^2 + v^2 + w^2)^0.5
Ref: Pg 113
A change in acceleration may be due to ____.
Change in speed or a change in direction (or both).
Ref: Pg 113
Describe the Eulerian method.
The Eulerian method used the field concept. In this case, the fluid motion is given by completely prescribing the necessary properties (pressure, density, velocity, etc) as functions of space and time. From this method, we obtain information about the flow in terms of what happens at fixed points in space as the fluid flows through those points.
Ref: Pg 115
Describe the Lagrangian Method.
This method involves following individual fluid particles as they move about and determining how the fluid properties associated with these particles change as a function of time.
Ref: Pg 115
True or False
Either Eulerian or Lagrangian methods can be used to describe flow fields.
True
Ref: Pg 115
True or False
No matter how much Lagrangian information can be accumulated, you can never derive Eularian data from it (or vice versa).
False. If sufficient information is present you can convert between either method.
Ref: Pg 115
In FM, which is usually easier to use; Eulerian or Lagrangian?
Eulerian.
Ref: Pg 115
Most flow fields are ______.
3-D
Ref: Pg 116
Give the definition of “steady flow.”
The velocity of a fluid particle at a given point in space doesn’t vary with time.
Extra Notes: This is listed by the index as the definition but it is used in looser terms in other areas of the book.
Ref: Pg 117 (Print Version)
True or False
In reality, almost all fluid flows are unsteady to some degree.
True
Ref: Pg 117
What are the three general types of unsteady flow?
- Non-periodic
- Periodic
- Random
Ref: Pg 117
Describe turbulent flow.
The unsteady character of a flow is seemingly random. There is no repeatable sequence or regular variation to the unsteadiness.
Ref: Pg 117
Define “streamline.”
A streamline is a line that is everywhere tangent to the velocity vector throughout a flow field.
Ref: Pg 74 and 118 (Print Version)
True or False
For unsteady flow, the streamlines do not change shape.
False
Ref: Pg 118
How does one go about obtaining the information necessary to plot streamlines?
Streamlines can be obtained analytically by integrating the equation defining lines tangent to the velocity field.
dy/dx = v/u
Ref: Pg 118
Give the definition of a “streakline.”
A streakline consists of all particles in a flow that have previously passed through a common point.
Extra Notes: These are much more commonly used as a laboratory tool rather than an analytical tool.
Ref: Pg 119
True or False
If the flow is steady, each successively injected particle follows precisely behind the previous one, forming a steady streakline that is exactly the same as the streamline through the injection point.
True
Ref: Pg 119
Define “pathline.”
A pathline is the line traced out by a given particle as it flows from one point to another.
Ref: Pg 119
True or False
For unsteady flow, a pathline will directly correspond to a streamline of the same particle.
False, the flow must be steady for this condition to be satisfied.
Ref: Pg 119
True or False
Pathlines, streaklines, and streamlines are the same for steady flow.
True.
Ref: Pg 119
Accleration is the ________ for a given particle.
The time rate of change of velocity.
Ref: Pg 121
True or False
The “substantial” derivative is analogous to the “material” derivative.
True
Ref: Pg 122
