slide 1 announcements/opportunities next year’s aircraft design class: –we will (again) have a...

Aerospace andOcean Engineering slide 1

Announcements/Opportunities

• Next year’s Aircraft Design class:

– We will (again) have a joint team with ME to build and fly a morphing airplane

– Send me email: [email protected] to apply

– We will have 4 AEs on this team

• Undergraduate research:

- lots of opportunities to help the design class software and do student AIAA papers, see me if you are interested.


AOE 3054AOE 3054Aerospace and Ocean Aerospace and Ocean

EngineeringEngineeringInstrumentation and LaboratoryInstrumentation and Laboratory

A Lectureon

Aerodynamic Testing

W.H. Mason


Overview

• Where you test

• Why you test

• How you test

• Some specifics for your lab


The NTF at NASA Langley

Hampton, VA

Performance: M = 0.2 to 1.20PT = 1 to 9 atmTT = 77° to 350° Kelvin

Feb. 1982


The Full Scale Tunnel at NASA Ames

80x120 FootTest Section

40x80 FootTest Section

Aviation Week & Space Technology, Dec. 7, 1987


Information Sources

• Lot's of introductory material on

Aero Test in the manual: read it!

• The standard reference book:

Barlow, Rae and Pope,

Low Speed Wind Tunnel Testing


Wind Tunnel Testing is Expensive

Preparation and planning are required to get into any tunnel:

• Make pre-test estimates

• Prepare a pre-test report including a Run Schedule


So Will the Computer Eliminate the WT?

Cost,Flowtime

Number of Simulations

10 100 1,000 10,000

E.N. Tinoco, (Boeing) “The Impact of CFD in Aircraft Design,”Canadian Aeronautics and Space Journal, Sept., 1998, pp. 132-144


Key Items

• Safety, accidents can happen

• Pretest Planning - the key to success

• Model Design

• The Run schedule

• Typical Tests:

- force and moment

both performance, stability, and control

- pressure distributions

- flow diagnostics

on and off surface flow visualization


Test Hours, F-16 WT Test

0 500 1000 1500 2000

general arrangementwing planform,camber

LE & TE flapsstrake developmentcontrol deflections

storesstore loads

pressure loadsinlet

flutterstore separation

spin/stallspillage and nozzle

miscellaneous


Research Fighter Configuration (RFC)Visualization with a Tuft Grid

Small Model in Grumman Tunnel


Another Way To Do Flow Diagnostics

Kurt Chankaya, Grumman (now Lockheed)


Typical way to put tufts on the wing

From Pope and Harper’s text, taken in the Wichita State tunnel


Oil Flows for Surface Visualization 1

SC3 Wing, M = 1.62, = 8° (nominally attached)


Oil Flows for Surface Visualization 2

SC3 Wing, M = 1.62, = 12° (TE flow separation)


Laser Light Sheet example

Aviation Week & Space Technology, July 29, 1985

Light Sheet from an argon laser, the flow is seeded with an standard smoke generator.

Northrop IR & D example of vortex flow over a delta wing configuration.

Exhibited at the 36th Paris air show.


Model Fabrication:

• Accuracy important!

- drag, under all conditions

- low speed near max lift

- transonic cruise condition


WT model with high LE accuracy Req’ts. Supercritical Conical Camber (SC3)

Wing, developed using CFD. The leading edge contour accuracy is critical.

Note the arc of the wingalong the trailing edge,a sort of “gull shape”


Inspecting the Model Leading Edge


Fab agrees with designed contour!


Simulation Issues

• Fundamental: Mach number and Reynolds number

- Match Mach, do your best on Reynolds, leads to:

- transition fixing

• Test issues:

- wall interference, flow angularity, nonuniformity

• Adjustment from model scale to full scale


Tunnel/Mounting Interference

Tunnel and Balance Centerline

Dmeas

Dtrue

LmeasLtrue

Walls restrict airflow around model

Flow angularity causes causes true forces to be

in a direction different than the reference

upV Exposed strut senses addtional drag

on external balance


Sue Grafton with RFC at NASA Langley


RFC in the 30x60 at Langley: static tests


Free Flight Setup: A complicated activity


RFC Model in Free Flight at Langley


The Tunnel


The Virginia Tech Stability Tunnel

• A high quality flowfield- uniform mean flow- low turbulence level- low flow angularity

• came from NASA in 1958• 6'x6' test section, 24 ' long• 600 hp motor/14' fan• 275 fps max speed


Virginia Tech Stability Tunnel Layout


Velocity Variation in the Test Section

0.96

0.98

1.00

1.02

1.04

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

V/Vref, U = 125 fps, Z = 0 ftV/Vref, U = 125 fps, Z = 0.5 ftV/Vref, U = 200 fps, Z = 0.0 ftV/Vref, U = 200 fps, Z = 0.5 ft

Virginia Tech Stability Wind TunnelMean Flow Calibration Characteristics

V/Vref

VPI Aero-161, Dec. 1987

y, ft


Upwash Variation in the Test Section

-1.50°

-1.00°

-0.50°

0.00°

0.50°

1.00°

1.50°

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Alpha, U = 125 fps, Z = 0 ftAlpha, U = 125 fps, Z = 0.5 ftAlpha, U = 200 fps, Z = 0.0 ftAlpha, U = 200 fps, Z = 0.5 ft


, y ft

-161, . 1987VPI Aero Dec


Sidewash Variation in the Test Section

-2.00°

-1.50°

-1.00°

-0.50°

0.00°

0.50°

1.00°

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

Beta, U = 125 fps, Z = 0 ftBeta, U = 125 fps, Z = 0.5 ftBeta, U = 200 fps, Z = 0.0 ftBeta, U = 200 fps, Z = 0.5 ft


β

, y ft

-161, . 1987VPI Aero Dec


Use a Strain Gage Force Balanceto Measure Loads

Tension change in wire changes resistance

You used one before?

• Assume that the balance is adequatelycalibrated - we will not check it this year


Strain Gages

strain gage element simple strain gage balance

true force balance circuit for balance

1 2

3 4

5 Volts

OutputVoltage

Load

StrainGages

1

2

l1

M

M

2

1

Δl

l2

1 2Δl

D =M M-

Load (D)

3

4

1

2

M = D l

M = D l

M - M = D(l - l )

= D Δl

1

1 12

2

2

1

2

x

x


Mechanics for this lab:

• two weeks

• 1st week - get ready

- check out tunnel, make pretest estimates

• 2nd week: test!

- run the model


The Tests!

New this year: we have 2 possibilities:

1. The “standard” rectangular wing

2. The Pelikan Tail (from a senior design project)

Your choice!


Objective:

Use Experimental techniques to find aero characteristics of:1. A rectangular, unswept wing

• with and w/o transition stripsor

2. A novel tail concept almost used on the Boeing JSF, and subsequently adopted by our senior UCAV-N team


The Rectangular Wing Model

6.0 "

Wing Mounting Holes

Trailing Edge

34.0 "

3.667"

(.98" between holes)

The airfoil: originally a Clark Y, recently modified (thickened) to strengthen the model - How does this change the test estimates?


Rectangular Wing Model Airfoil Section

-0.05

0.00

0.05

0.10

0.15

0.20

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2

CLARK Y Airfoil for Aero Lab TestTheoretical Coordinates and Coordinates after Wing reinforcement

y/c uppery/c lowery/c measured

y/c

x/c

Not to scale


Expected Lift Coefficient Variation: Rectangular Wing Model

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

-15° -10° -5° 0° 5° 10° 15° 20° 25°

CL

, .deg

,Estimate( )Inviscid Theory

Clark Y Airfoil = 5.6 AR Rectangular Wing

NACA data = 1.0 10Re x6

,VPI data = .3 10Re x6


Expected Pitching Moment: Rectangular Wing Model

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

-0.15-0.10-0.05-0.000.05

CL

CmCm

Clark Y AirfoilAR = 5.6 Rectangular Wing

NACA data,Re = 1.0x106


Expected Drag Coefficient Variation: Rectangular Wing Model

-0.30

-0.00

0.30

0.60

0.90

1.20

1.50

0.00 0.05 0.10 0.15 0.20

CL

CD

NACA Data, Clark Y airfoil, rectangular wing, AR = 5.6, Re = 1x10 6

Theoretical 100%Suction Polar, e = .98

Theoretical 0% Suction Polar

Wind tunnel test data

Note: Theoretical polars shifted to match experimental zero lift drag


The Pelikan Tail

= HINGE LINE


Pelikan Tail Plan View


Let those seniors talk?

• Why should you do this?


Wind Tunnel Testingis

Fun!

Good Luck

slide 1 announcements/opportunities next year’s aircraft design class: –we will (again) have a...

Documents

lockheed slide

mason slide

lab slide

attached slide

wt test slide

grumman tunnel slide

run schedule slide

model leading edge slide