A Brief Introduction to Fl id M h i (CE 251)Fluid Mechanics (CE 251) · 2012. 8. 27. · A Brief...
Transcript of A Brief Introduction to Fl id M h i (CE 251)Fluid Mechanics (CE 251) · 2012. 8. 27. · A Brief...
A Brief Introductionto
Fl id M h i (CE 251)Fluid Mechanics (CE 251)
Fall 2012Fall 2012Prof. Brandes
What is a Fluid?
Solid BehaviorSolid Behavior(ES 230)
G h d l
G = shear modulus
fluid behavior → infinite strain
Fluid Behavior
= viscosity (resistance to flow) = viscosity (resistance to flow)
d/dt the Rate of angular def
– So, a fluid is a substance that deforms without bound when subjected to shear i e it “flows” : bound when subjected to shear, i.e. it flows : water, air, honey, beer, etc
li i f fl id h iApplications of fluid mechanics water supply, pipelines,
conveyance systems
stormwater management
hydromachinery (pumps, turbines, propellers)
flood waves, groundwater
weather prediction, windpower, aerodynamics
medicine
i l li iA practical application:
on to some important concepts in Chapter 1 concepts in Chapter 1
THE FLUID AS A CONTINUUM – We don’t care too much what the individual
molecules are up to, we’ll look at lots of pthem together – thus, the fluid as a CONTINUOUS medium
DIMENSIONS “Dimensional Homogeneity”
– Equations derived from fundamental principles Equations derived from fundamental principles of math and physics must have the same dimensions (M, L, t, T) on both sides of the =
constantVzp
2constant
gz
2
LLfC
Re1520
)Re06.0(ln523.0
2 ??LL )(
DIMENSIONS
UNITS1. Don’t switch units (e.g., English to SI)2. Carry units through calculations, don’t add y g
what you think the units should be at the end
EX: a 55-gal drum of water weighs what?
lbsft3 lbsftlbsx
galftxgal 8.4584.6248.7
55 3
3. Check your units at the end to see that they make sense!make sense!
C ts f Fl id M h i sComponents of Fluid Mechanics1) Hydrostatics – distributed loads on submerged 1) Hydrostatics – distributed loads on submerged
objects due to static water pressures
2) Hydrodynamics - theoretical, mathematical equations of fluid flow– theorists: Newton , Bernoulli
3) Hydraulics - empirical (experimental) 3) Hydraulics empirical (experimental) measurements of fluids, fitted to mathematical functions
i t li t D Vi i R ld Nik d F d– experimentalists: Da Vinci, Reynolds, Nikuradse, Froude