Golf ball dimple concept in action
Global Hawk
Turbine Blade CFD
Re = 25,000
Turbine Blade CFD
with Dimples
GR#1 Review Bring calculator, pencils & your brain Calculator policy: “This examination is CLOSED
BOOK/CLOSED NOTES. You are allowed a calculator, a straight edge, and an exam supplement as resource materials for this exam. However, you may not use your calculator's memory functions to store course notes, memory equations or homework solutions.”
Point breakdownMultiple choice conceptual – 65Multiple choice short work – 50Long workout – 35Total points – 150
Understanding the concepts and definitions, and being familiar with the equations we’ve used so far, are keys to success
History of Aeronautical Design
1. Sir George Cayley
2. Otto Lilienthal
3. Samuel Langley
4. Wright Brothers
a) Secretary of the Smithsonian; $50,000 US grant to develop a powered airplane; developed efficient internal combustion engine; aircraft design neglected need for control
b) First to propose separate lift & thrust mechanisms; developed basic requirements for stability and control; researched alternatives to steam power
c) Tested airfoils in wind tunnel; built and flew gliders; used wing warping and full elevator to control aircraft; first successful crewed, heavier-than-air sustained flight on Dec 17, 1903
d) The Glider Man with over 2500 flights; first successful man-carrying glider in 1891
Introduction to Aircraft Design
Why design a brand new airplane? _________________________________
Who defines the need? _________________________________
List the three steps in the design cycle: _________________________________
List the three design phases: _________________________________
to satisfy a need
the user
synthesis, analysis, decision making
conceptual, preliminary, detail
Flow Properties
List the four fundamental flow properties: _____________________________________
These four flow properties are ______ properties
P, , T are _______ quantities, while V is a _______ quantity
Units P: : T: V:
pressure, temperature, density, velocity
point
vectorscalar
lb/ft2 or N/m2
slugs/ft3 or kg/m3
°R or Kft/s or m/s
Equation of State The equation of state we use for gases is the
____________________________________ This relation applies at a _______ for gases:
The gas constant (R) for air is ___________________________
A gas that obeys the perfect gas law is called a _______________
perfect gas law: P = RT
pointat moderate temperatures and pressuresno chemical reactions or molecular breakupsvery low molecular attraction
1716 ft•lb/sl•°R or 287 N•m/kg•K
perfect gas
Hydrostatic Equation
The hydrostatic equation (______________) says that as height increases, ___________ ____________
To derive the hydrostatic equation, we must assume a ________ fluid (sum of vertical forces is zero)
If we assume = _________ (as for _________), we can integrate the hydrostatic equation to obtain the manometry equation: __________________
dP = -g dhpressure
decreases
static
constantliquids
P2 – P1 = -l g(h2-h1)
Standard Atmosphere The standard atmosphere tabulates values of
_________, ____________, and ________ at various altitudes
In deriving the standard atmosphere (three unknowns), we had only two equations: ________________________________________
To develop the third equation, we used balloon flights to measure ______________ in the atmosphere
You are flying at 32,000 ft on a standard day. What is the atmospheric pressure? _______________ Temperature? _______________
You are flying at a pressure altitude of 7.0 km. What is the atmospheric pressure? _______________ Temperature? _______________
pressure temperature density
perfect gas law and hydrostatic equation
temperatures
574.6 lb/ft2
404.8°R
41,105 N/m2
don’t know!
Standard Atmosphere You are flying at a geometric altitude of 14,000 ft, a
pressure altitude of 15,000 ft, and a temperature altitude of 16,000 ft. What is the outside air density? __________________________________________
A thermometer mounted to your aircraft measures an air temperature of 242.71 K. What is your temperature altitude? _______________
The tropopause divides the _____________ from the ______________; for several tens of thousands of feet above the tropopause, standard air temperature __________________
An altimeter is just a __________ gauge calibrated in units of __________ instead of __________
= 1195 lb/ft2 / (1716 ft•lb/sl•R • 461.7°R) = 0.001508 sl/ft3
7.0 kmtroposphere
stratosphere
remains constantpressure
pressurealtitude
More Aero Definitions Flow field: specification of _________________ in a
_________________________________ Steady flow: flow in which properties at a ________ are
invariant with respect to _______ Streamline: imaginary line (curve) where the flow is
_________ to the line at every point Flow ________ cross a streamline
Streamtube: collection of _____________ passing through a plane ____________________ to the flow direction
One-dimensional (1-D) flow: properties are __________ across the cross section of the flow and vary only in the ________ direction
A point where flow velocity slows to zero is a ____________ point; the associated streamline is a _____________ streamline
aero propertiesregion of interest
pointtime
tangentcannot
streamlinesperpendicular
constantflow
stagnationstagnation
Mass Flow Rate and theContinuity Equation
If we assume ____ flow, we can calculate mass flow rate: m = _______
If we assume ________ flow through a streamtube, then no mass is being stored (and mass is neither created nor destroyed), and m = ____________
The continuity equation is the expression of the principle of ________________________ for fluid flows
Continuity equation: _________________ For incompressible ( = const) flows, such as
_________, and air slower than __________ ____________________, the continuity equation reduces to _____________
.
.
1-DAV
steady
constant
conservation of mass
1A1V1 = 2A2V2
liquids 100 m/s or330 ft/s or 225 mph
A1V1 = A2V2
Sources of Aerodynamic Forces
__________ forces: act ________ to the surface
__________ (_________) forces: act ____________ to the surface
Pressure normal
Shear viscoustangential
Euler’s Equation, Bernoulli’s Equation Euler’s Equation (____________) assumptions:
Bernoulli’s Equation (_________________________) additional assumption:
Bernoulli’s Equation says that ________________ is constant along a ____________
P represents ________ pressure and ½v2 represents _________ pressure (__)
P + q = P0 (_______ pressure) A pitot tube measures _______ pressure
dP = -V dVFlow along a streamlineSteady flowBody forces (gravity/magnetic) negligibleInviscid (frictionless) flow
P∞ + ½V∞2 = P1 + ½V1
2
Incompressible flow ( = constant)total pressure
streamlinestatic
dynamic qtotal
total
Airspeed Measurement and ICeT I___________ airspeed: ______________
__________________________________ C___________ airspeed: corrected for
_______________________; VC = __________ e___________ airspeed: corrected for
_______________________; Ve = __________ T___________ airspeed: corrected for
_______________________; VT = ___________ Ground speed: aircraft velocity relative to the
________; VG = __________ Dynamic pressure: q = ½V2 = ½SLVe
2
Be prepared to work backwards!
ndicated what you seeon your airspeed indicatoralibrated
position error VI + VP
quivalentnon-standard pressures f•VC
ruenon-standard densities ρ
ρV SLe
ground VT + Vwind
Viscous Flow Profile (viscous) drag is composed of _______________ drag
and __________ drag V = __ at the surface of a solid object (_________ condition) Viscosity is the tendency for a fluid to resist
__________________________ Viscosity can be described as ______________________ For liquids, viscosity ___________ at higher temperatures; for
gases, viscosity ___________ at higher temps The edge of a boundary layer is considered the location
where V = ___% of the local freestream velocity _______ pressure remains constant through the boundary
layer; ________ pressure decreases toward the surface _______ effects are only important in the boundary layer;
outside the boundary layer, we can assume __________ flow
skin frictionpressure
0 no-slip
velocity discontinuitiesresistance to flow
decreasesincreases
99Static
dynamicViscous
inviscid
Viscous Flow Reynolds number, a ______________ parameter, is the ratio of
__________ forces to _________ forces (Re = ___________)
Viscous forces dominate in a _________ boundary layer; inertial forces dominate in a ___________ boundary layer
Transition: boundary layer changes from _________ to ___________; Reynolds number at the transition point is __________
As a rule of thumb, ReXcrit ≈ _________; locations where Re > ReXcrit have ___________ boundary layers
Turbulent boundary layers have ________ dV/dy at the wall, so they produce ______ skin friction drag
Boundary layer transition can be affected by: ______________________________________________________________________________________________
Pressure drag is also known as drag due to ____________; flow separation occurs when flow momentum cannot overcome an ___________ (or unfavorable) pressure gradient (dP/dx ___ 0), i.e. when dV/dy = ____
dimensionlessinertial viscousVx/
laminarturbulent
turbulentlaminar
ReXcrit500,000
turbulenthigh
more
surface roughness; freestream turbulence; aircraftvibration; heat transfer; adverse pressure gradient
separation
adverse> 0
Viscous Flow Flow separation causes a ___________ in lift and an
__________ in pressure drag Pressure drag is the result of the loss of _______
pressure in the boundary layer and thus a _______ pressure imbalance
___________ boundary layers have higher V close to the surface, and _________ separation and ___________ pressure drag
Dimples on a golf ball help transition the boundary layer to ___________, delaying __________ and reducing ________ drag
For blunt objects, skin friction drag is _____ important, pressure drag is _____ important, and ____________ BL is preferred
For streamlined objects, skin friction is _____ important, pressure drag is _____ important, and ___________ BL is preferred
reductionincrease
totaltotal
Turbulentdelay
reduce
turbulent separationpressure
less
less
more
moreturbulent
laminar
Example ProblemYou are flying at a pressure altitude of 15,000 ft. Outside air temperature is -5°F. Your indicated airspeed is 130 kts; your flight manual indicates a position error of -5 kts. At a point on the upper surface of the wing, the velocity is determined to be 300 ft/s.a) Determine the outside air density
b) Determine your true airspeed
c) Determine the static pressure acting on the upper surface of the wing
(Use perfect gas law: = 0.001531 sl/ft3)
(Incompressible, so use Bernoulli:P∞ + ½V∞
2 = Pwing + ½Vwing2 Pwing = 1178.8 lb/ft2)
(Use ICeT: VT = V∞ = 155.3 kts = 262.46 ft/s)
Final Hints
Review homework problems 1–15 Review lesson 2–7 readings – handouts are
useful! Be very familiar with your green supplemental
data package (clean copy available for GR) Know “memory” equations (handout package) If desired, review lesson slides on k: drive (k:\
campus\df\dfan\ae315\instructor folders\ McCann)
I’ll be home Sunday for last-minute questions