Fluid Mechanics Flashcards
study of fluids at rest in equilibrium situations
Fluid statics
study of fluids in motion
Fluid mechanics
Application Areas of Fluid Mechanics (7)
- Industrial applications
- Piping and plumbing systems
- Aircraft and spacecraft
- Human body
- Natural flows and weather
- Power plants
- Boats
Intermolecular bonds are strongest in _______ and weakest in __________.
solids
gases
The molecules in a _____ are arranged in a pattern that is repeated throughout.
Solid
In _________ molecules can rotate and translate freely
liquids
In the ____ phase, the molecules are far apart from each other, and molecular ordering is nonexistent
gas
The arrangement of atoms in different phases:
(a) molecules are at relatively fixed positions in a ________ ,
(b) groups of molecules move about each other in the ________ phase, and
(c) individual molecules move about at random in the ______ phase.
a. solid
b. liquid
c. gas
In a liquid, groups of molecules can move relative to
each other, but the volume remains relatively constant
because of the ___________ between the
molecules. As a result, a liquid takes the shape of the
container it is in.
strong cohesive forces
A gas expands until it encounters the walls of the
container and fills the entire available space. This is
because the gas molecules are widely spaced, and the
________________ between them are very small. Unlike
liquids, a gas in an open container cannot form a free
surface
cohesive forces
A _________ is any substance that can flow
fluid
___________ or more precisely, the ______________, of a substance is its mass per unit volume, for a pure substance the density has the same numerical value as is mass concentration. Each materials have different ___________.
Density or Volumetric mass density
is the ratio of the density of a substance to the density of a reference substance;
equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume
specific gravity
ratio of an object’s density to the density of water at 4.0 oC
specific gravity (s.g.) or “relative density” = 1000 kg/m3
It is a dimensionless quantity
specific gravity
If a substance’s relative density is less than one then it is ___________ than the reference;
if greater than 1 then it is ________than the reference.
If the relative density is exactly 1 then the densities are _______
less dense
denser
equal
defined as the normal force F per unit area A over which the force is applied.
pressure
Does not require a knowledge of the behavior of individual molecules and provides a direct and easy way to analyze engineering problems
Macroscopic` or classical approach
Based on the average behavior of large groups of individual molecules.
Microscopic or statistical approach
_________ at a point is defined as the normal force per unit area
Pressure
a small surface of area (dA) within a fluid at rest:
The surface does not accelerate, so the surrounding fluid exerts equal _______ forces on both sides of it.
The fluid cannot exert any force parallel to the surface, since that would cause the surface to ______
normal forces
accelerate
The pressure at the top is the_____________.
The pressure at the bottom has the same value p.
The pressure is the same at any two points at the same level.
The shape of the container does not matter.
atmospheric pressure
- pressure of the earth’s atmosphere
- varies with weather changes and with elevation.
atmospheric pressure
At sea level the normal atmospheric pressure is ___ atmosphere (atm) is given by _________ Pa.
1 atm = 1.013x10^5 Pa.
Pressure is measured using two references:
- Atmospheric pressure
- Absolute vacuum/zero pressure
difference between unknown pressure and atmospheric pressure
Gauge pressure
true pressure; includes the atmospheric pressure
Absolute pressure
Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel.
Pascal’s Law
________’ principle:
When a body i s completely or partially immersed in a fluid, the fluid exerts an upward force, called the ________, on the body equal to the weight of the fluid displaced by the body.
Archimedes
buoyant force
occurs because the upward pressure on the bottom surface of a submerged object is greater than the downward pressure on top of its surface
Buoyant force
is equal to the weight of the displaced water
the buoyant force
If the object is totally submerged, the direction of motion of an object submerged in a fluid is determined only by the ________of the object and the fluid.
densities
density of object < density of fluid
Fg < B
object accelerates upward
density of object > density of fluid
B < Fg
object sinks
if the object is _______
- the fraction of the volume of a floating object that is below the fluid surface is equal to the ratio of the density of the object to that of the fluid.
- the upward buoyant force is balanced by the downward gravitational force acting on the object.
floating (partially submerged),
The flow becomes _________ if the fluid’s speed exceeds a certain critical value. If this is the case,
Bernoulli’s equation cannot be used.
turbulent
The product is the volume _________, the rate at which volume crosses a section of the tube: Av = delta V / delta t
flow rate
The speed of water spraying from the end of a garden hose _________ as the size of the opening is decreased with the thumb.
increases
The principle states that “the pressure of a fluid [liquid or gas] decreases as the speed of the fluid increases.
Bernoulli’s principle
Within the same fluid (air in the example of aircraft moving through air), high-speed flow is associated with low pressure, and low-speed flow is associated with high pressure.
Bernoulli’s principle
states that the work done on a unit volume of fluid by the surrounding fluid is equal to the sum of the changes in kinetic and potential energies per unit volume that occur during the flow
Bernoulli’s principle
is the principle that allows wings to produce lift and planes and helicopters to fly. There are many factors that can effect the lift produced under this principle, but in order to fully understand how and why things can effect flight one must understand how Bernoulli’s principle works.
Bernoulli’s Principle
