Fluids; School of PE Flashcards
Fluids
Provide the following with SI Units
Density of Water?
Unit Weight of Water?
What temperature is the water for these equations
4 degrees centigrade
Fluids
What would be classified as a Fluid
Liquids and gasses are fluids
Fluids
What is the difference between a a fluid and a solid at a molecular level?
Can Fluids support shear?
Fluids Moleculse not tightly packed, where they are tightly packed in a solid.
FLuids can not support shear.
Fluids
What is Density?
Provide other name for it.
Density is mass per unit volume
Also called mass density
Fluids
What is specific weight?
Weight per unit volume
mass * gravity divided by volume
mass density * gravity
Fluids
Explain how density cahnges for gasses, fluids, and solids
Gasses are highly compressible, so density is not cnstant; Gass density will depend on the temperature and pressure.
Fluids density is somewhat incompressible, so look at it as the density is constant
Solids the density are constant and inconpressable
Fluids
Specific Volume-
Volume per unit mass; or inverse of the density
not commonly used
Fluids
When we talk about density, the most important fluid we talk about is ______.
Density of Water standard is measured at ___ degrees centigrade.
Water
4 degrees centigrade
Fluids
What is Specific Gravity
Explain stipulations
Specific Gravity is the ratio of the density of 2 fuids.
Usually compared to water for liquid
Usually compared to air as standard temperatue and pressure.
Gasses use the STP= 0° C (273 Kelvin) 1 atmosphere
Water- STP is measured at 4° C; Density = 1000 kg.m3 and Unit wieght is= 9800 N/m3
Fluids
What are the 2 components when talking about Shear Stress for a fluid
The component normal (perpindicular) to the surface
the component the tangential to the surface
Fluids
What does Laninar mean for fluids
It means the fluid is moving in layers
Fluids
Other 2 names for viscosity
dynamic viscosity
absolute viscosity
All use the greek letter mu to signify them
Fluids
For a Newtonian Fluid, what is the shear stress-
Shear stress is equal to the viscosity times the shear deformation rate
For a newtonian fluid the shear deformation rate is raised to 1; Loos at figure
If n is not 1, then it is a non-newtonian fluid
Fluids
For anewtonian fluid, provide equation for viscosity
Viscosity is equal to the Shear stress divided by the shear deformation rate.
Fluids
What equation should be used for any fluid regardless iif it is newtonian or not (This is a Newton Law)
Same equation for Newtonina, just uses k in place of mu for viscosity, and the shear deformation rate is raised to a power of n
Fluids
For fluids that are non-newtonian, explain the n value, and name the 2.
What fluid kind of acts like a newtonian fluid, but requires a significant amount of shear stress before they begin moving
Pseudoplastic n < 1
dilatant n > 1
Bingham; Drilling mud is a good exaple; soft solids or thick liquids
Fluids
Kinematic Viscosity
What euqatin is this uses in alot
Mu divided by rho
viscosity divided by density
used for reynolds number alot.
Fluids
What does Surface Tension depend on?
depends on the properties of the fluids at the surface or interface
Between water and air then called surface
Between water and another material (like oil) then called interface
Fluids
What is Cohesion and when is it more dominant?
What is adhesion and when is it it more dominant?
The fluid gos down in the tube when cohesion becasue the fluid wants to stay together.
Cohesion is more dominant when dealing with mercury
Adhesion the fluid likes the surface so raises in tubes.
Adhesion is more dominant when dealing with water
Water likes the glass more then it likes its own molecules
Angle Beta is the angle the fluid is making with the surface.
Fluids
In fluid mechanics we always use what pressure?
Gauge pressure
Fluids
Provide equation for absolute pressure.
Fluids
Provide equation for Hydrostatic Pressure
Fluids
What is a manometer used to measure
How do you measure?
Measures the pressure difference b/w 2 points.
Always start from one end (preferably open end) and preceed to the other end.
A differential manometer has 2 closed ends. Approach is still the same.
If the mamometer was open, the PB=0; There is atmospheric pressure, but only interested in gauge pressure which is zero
Fluids
What do we use to measure atmospheric pressure
A Barometer
refer t0 pg 70 of ncees
Try to choos a liquid that the vapor pressure is so small you can igonore it (like mercury), or choos what you can find a value to like water (pg 70)
Fluids
What is Average pressure?
What is Resultant Force?
(P1 + P2) / 2
x A
Inclined surface area= area of inclined surface.
Fluids
Pressure = ?
Fluids
What is Archimedes Principle for?
Equation-
For objects that are partially submerged.
Fluids
When talking about archimedes prinicile, what must hold true for the object to be stable.
In order to be stable the center of gravity should always be below the center of buoyancy
Fluids
Provide Equation for Conservation of mass of coninuity equation
Fluids
What does Q stand for
Fluid flow
Fluids
Provide conservation of mass (Continuity) Equation for incompressible fluid
Density is same, so cancelled out for this equation
Define Conservation of Energy (Also called ?)
This type of fluid is also called ?
Provide Equation shen expressed as distances or heads-
Total energy in the system must be conserved
Bernoulli Equation
Used for Ideal Fluids
Pressure Energy + Kinetic Energy + Elevation Energy
Fluids
Conservation of Energy (Bernoulli Equation) can also be expresses as specifc energy for ideal fluids only (In real life situation there is alwasy be losses)
Provide Equation
What is specific energy
Specific Energy is the energy per unit mass
This equation is the regular Conservation of energy equation multiplied by g (gravity)
Fluids
When looking at conservation of energy there will always be losses. The conservation of energy equation then adds in the fitting losses.
Provided equation
Losses are always expresses as a function of ??
kinetic energy/ or velocity head (See Picture)
Fluids
Equation for determining frction losses for the conservation of Energy Equation for a same size pipe with no elevation changes
Fluids
What does laminar mean
If you take a round conduit with laminar flow, explain the velocity within the conduit
Provide equation for velocity distribution for laminar flow
one layer moving over another layer
Velocity = zero at surface
Velocity is max at center
