Chapter 4: Fluid kinematics Flashcards
What is a velocity field?
The velocity field could be a time dependent 3d vector field.
Describe the Eulerian field description method
The Eulerian field description is represented with a velocity field, where the velocity is described with a vector at each point.
Describe the Lagrangian field description method
Follow a particle through the flow. The particle is identified by position at an initial time.
What are three ways to visulaize a flow?
By streamlines, streaklines, and pathlines. For a steady flow these are all the same.
What is a streamline and how is it calculated?
A line tangent to the velocity at every point along the line.
dy/dx=v/u Then integrate.
What is a pathline and how is it calculated?
Line describing the actual path of a fluid element.
dx/dt=u.
A derivative in a lagrangian sense.
What is a streakline and how is it calculated?
A line made up of the particles that previously pased through a common point.
What is the acceleration field and how do you calculate it?
By deriving the velocity field with respect to time the acceleration field is given.
Dv/Dt=(v dot grad)v+partial(u)/partial(t)
What is the local acceleration term?
partial(u)/partial(t)
What is the convective term?
(v dot grad)v
What is a system?
A collection of matter of fixed identity.
e. g dyed fluid elements
- Controlled mass
- Lagrangian concept: Moving with the fluid
What is a control volume?
- Some volume fixed in space
- Eulerian concept
- Has a boundary called “Control surface”
Why do we need Reynolds transport theorem?
Because most physical laws are stated for a system and if we want to express them for a control volume we need to rewrite the expression using RTT.
What is an extensive property?
A property that scales with the system size e.g mass volumet etc. Often denoted with capital letters.
What is an intensive property?
A property that doesnt scale with the size of the system.
often denoted with lower case letter.
b=B/m
