Chapter 1 Flashcards
What is a fluid
Substance that flows
Of the three primary phases, which are fluids
Liquid and gas
The no slip condition
The fluid particles immediately at the wall are attached to the wall and move with the wall, same velocity. This is due to viscosity.
Viscosity
The state of being sticky, thick, and semi fluid due to internal friction
Flow
Fluids cannot resist, sheer, therefore they flow
What differentiates, gas and fluid
Gas-fills the container, higher atomic energy.
Fluid- does not fill the container. Tighter atomic spacing. It has a free surface and experiences the effects of gravity.
Free surface
is the surface of a fluid that is subject to zero parallel shear stress, such as the interface between two homogeneous fluids.
Continuum
You want to ignore it intermolecular voids. And allows you to take the average of total pressure and temperature which cannot be found in avoid. It is smooth with no discontinuity.
What cannot be defined in a void
Temperature, which is related to atomic energy. And pressure which is collision forces.
When does continuum hold?
If knudsen number is below 0.01 then the assumption holds
Nondimensional numbers
No dimensions, but allow for comparison between different flows
Knudsen number
Lambda -the main free path or average distance between molecules that they must travel to collide with each other
L- most important characteristic length
Kn= lambda/L
Lambda of Air at 1atm and 20C
6.3x10^-8
Density
Mass of a substance/volume (p=m/V)
Specific volume
Volume/mass (v= V/m)
Specific gravity
Relative density SG= P/Ph2o
Ph2o at 4C is 1000kg/m^3
Specific weight
Weight density: γ= pg
For gas what is density proportional to?
Density is proportional to P/T
Are liquids compressible
They are but only under extreme circumstances that are not relevant to this course
Density is a function of ____
Temperature
Pressure
A normal force exerted by a fluid per unit area. P=F/A
10^5 Pa
1 bar
1 atm
101325 Pa
Is pressure a vector or a scalar
A scalar, it has no direction
Pressure gauge
Is Pabs-Patm
Pvac
Pvac = Patm-Pabs
Pressure variation with depth
Influence pressure increases with depth due to the weight of the fluid above. It should be a perfectly linear relationship.
Pascals Law
Confined incompressible fluids at rest, an external pressure applied to the fluid is transmitted, uniformly and undiminished, and all directions through the fluid
