Chapter 3 - Fluid Dynamics

Pressure is a scalar or vector quantity?

scalar

Pressure acts in ____________ direction

all directions

Difference between atmospheric pressure and gage pressure [psi]

14.6 psi

Total pressure under a given depth of fluid of given density

Patm + ρgh

If there is a flow, then there is _________ which creates a ____________ reaction force

energy , shear

If there is no flow, then the only energy is _____________

normal stress

Pressure is a _____________ force

compressive

Pressure (eqn) =

= ρgh

Pascal’s Principle

change in pressure in an enclosed fluid is consistent throughout the fluid

Pressure measurement devices (2)

barometer, manometer

What does a barometer measure?

atmospeheric pressure

Atmospheric pressure is aka

barometric pressure

2 different kinds of manometers

u-tube, incline tube

Which manometer is more precise and why?

incline tube is more precise because you measure the incline length which is longer and therefore more precise

How many feet of water is equal to atmospheric pressure?

33 ft

At what depth of mercury is it equal to atmospheric pressure?

76 cm

Bourdon tube (What is it, mechanical or electric, how sensitive is it, and what is its application)

flexible spiral tube that senses movement; mechanical; not very precise; measures applied pressure

Pressure Transducer? (What is it, mechanical or electric, how sensitive is it, and what is its application)

converts the pressure effect to an electrical effect such as a change in voltage, resistance, or capacitance; electric; very precise, moreso than mechanical devices; variety of pressure tranducers measure gage, absolute, and differential pressures

Gage pressure transducers

use the atmospheric pressure as a reference by venting the back side of the pressure-sensing diaphragm to the atmosphere, and they give a zero signal output at atmospheric pressure regardless of altitude.

Absolute pressure transducers

calibrated to have a zero signal output at full vacuum.

Differential pressure transducers

measure the pressure difference between two locations directly instead of using two pressure transducers and taking their difference.

Strain-gage pressure transducers (What is it, mechanical or electric, how sensitive is it, and what is its application)

work by having a diaphragm deflect due to the pressure inputs, the strain gage stretches and a Wheatstone bridge circuit amplifies the output; electric

deadweight tester (What is it, mechanical or electric, how sensitive is it, and what is its application)

device made with an internal chamber with a piston and plunger to measure pressure put on the fluid inside; mechanical; used primarily for calibration; can measure extremely high pressures

hydrostatics

fluid statics

hydrostatics on plane surfaces

form a system of parallel forces, determine the magnitude of the force, the direction of application, and the position at which it is acting, aka, center of pressure.

The pressure at the centroid of a plane surface is equivalent to

the average pressure on the surface.

Understand equations and forces of inclined submerged planes

moments, forces, distances, volume of pressure prism, etc.

Hydrostatics on a curved submerged surface

FR = √(FH2+FV2) summation of horizontal and vertical forces by the fluid

hydrostatics on flat/horizontal plane surface

FR = ρgh꜀

buoyancy discovered by

Archimedes

buoyancy occurs when an object is __________

submerged

buoyancy always acts in the ____________ direction

upwards

buoyancy force =

weight of the fluid displaced; ρ*Vdisp*g

if Weight < Buoyancy Force

accel. up/float

if Weight > Buoyancy Force

accel. down/sink

if Weight = Buoyancy Force

no accel

stability is made of up

statics and buoyancy

stable means the CG is ______ the CB

below

unstable means the CG is ______ the CB

above

neutral means the CG is ______ the CB

same as

metacenter

the point of intersection between two vertical lines, one line through the center of buoyancy of the hull of a ship in equilibrium and the other line through the center of buoyancy of the hull when the ship is inclined to one side

a ship will overturn if its metacenter is ___________ its CG

below

to remain upright/stable, a ship's metacenter must remain _________ its CG

above

body force

weight, volume

surface force

pressure, area

define pressure prism

visual representation of hydrostatic pressure increasing with depth