1. Aero Engineering 315
Lesson 10 GR#1 Review

2. Golf ball dimple concept in action
Global Hawk
Golf ball dimple concept in action
Turbine Blade CFD
Re = 25,000
Turbine Blade CFD
with Dimples

3. 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 breakdown
Multiple choice conceptual – 65
Multiple choice short work – 50
Long workout – 35
Total points –
Understanding the concepts and definitions, and being familiar with the equations we’ve used so far, are keys to success

4. History of Aeronautical Design
Sir George Cayley
Otto Lilienthal
Samuel Langley
Wright Brothers
Secretary of the Smithsonian; $50,000 US grant to develop a powered airplane; developed efficient internal combustion engine; aircraft design neglected need for control
First to propose separate lift & thrust mechanisms; developed basic requirements for stability and control; researched alternatives to steam power
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
The Glider Man with over 2500 flights; first successful man-carrying glider in 1891

5. 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

6. pressure, temperature, density, velocity
Flow Properties
List the four fundamental flow properties: _____________________________________
These four flow properties are ______ properties
P, r, T are _______ quantities, while V is a _______ quantity
Units P: r: T: V:
pressure, temperature, density, velocity
point
scalar
vector
lb/ft2 or N/m2
slugs/ft3 or kg/m3
°R or K
ft/s or m/s

7. 1716 ft•lb/sl•°R or 287 N•m/kg•K
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 = rRT
point
at moderate temperatures and pressures
no chemical reactions or molecular breakups
very low molecular attraction
1716 ft•lb/sl•°R or 287 N•m/kg•K
perfect gas

8. 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 r = _________ (as for _________), we can integrate the hydrostatic equation to obtain the manometry equation: __________________
dP = -rg dh
pressure
decreases
static
constant
liquids
P2 – P1 = -rl g(h2-h1)

9. Standard Atmosphere pressure temperature density
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!

10. Standard Atmosphere 7.0 km troposphere stratosphere remains constant
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 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 __________
r = 1195 lb/ft2 / (1716 ft•lb/sl•R • 461.7°R) = sl/ft3
7.0 km
troposphere
stratosphere
remains constant
pressure
altitude
pressure

11. More Aero Definitions aero properties region of interest point time
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
region of interest
point
time
tangent
cannot
streamlines
perpendicular
constant
flow
stagnation
stagnation

12. Mass Flow Rate and the Continuity 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 (r = const) flows, such as _________, and air slower than __________ ____________________, the continuity equation reduces to _____________ .
rAV
steady .
constant
conservation of mass
r1A1V1 = r2A2V2
liquids
100 m/s or
330 ft/s or 225 mph
A1V1 = A2V2

13. Sources of Aerodynamic Forces
__________ forces: act ________ to the surface
__________ (_________) forces: act ____________ to the surface
Pressure
normal
Shear
viscous
tangential

14. Euler’s Equation, Bernoulli’s Equation
dP = -rV dV
Euler’s Equation (____________) assumptions:
Bernoulli’s Equation (_________________________) additional assumption:
Bernoulli’s Equation says that ________________ is constant along a ____________
P represents ________ pressure and ½rv2 represents _________ pressure (__)
P + q = P0 (_______ pressure)
A pitot tube measures _______ pressure
Flow along a streamline
Steady flow
Body forces (gravity/magnetic) negligible
Inviscid (frictionless) flow
P∞ + ½rV∞2 = P1 + ½rV12
Incompressible flow (r = constant)
total pressure
streamline
static
dynamic q
total
total

15. Airspeed Measurement and ICeT
ndicated
what you see
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 = ½rV2 = ½rSLVe2
Be prepared to work backwards!
on your airspeed indicator
alibrated
position error
VI + DVP
quivalent
non-standard pressures
f•VC
rue
non-standard densities
ground
VT + Vwind

16. Viscous Flow skin friction pressure no-slip velocity discontinuities
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
pressure
no-slip
velocity discontinuities
resistance to flow
decreases
increases 99
Static
dynamic
Viscous
inviscid

17. Viscous Flow dimensionless inertial viscous rVx/m laminar turbulent
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 = ____
inertial
viscous
rVx/m
laminar
turbulent
laminar
turbulent
ReXcrit
500,000
turbulent
high
more
surface roughness; freestream turbulence; aircraft
vibration; heat transfer; adverse pressure gradient
separation
adverse
>

18. Viscous Flow reduction increase total total Turbulent delay reduce
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
increase
total
total
Turbulent
delay
reduce
turbulent
separation
pressure
less
more
turbulent
more
less
laminar

19. Example Problem
You 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: r = sl/ft3)
(Use ICeT: VT = V∞ = kts = ft/s)
(Incompressible, so use Bernoulli:
P∞ + ½rV∞2 = Pwing + ½rVwing2  Pwing = lb/ft2)

20. 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