AERODYNAMICS AND WINDTUNNELS

AERODYNAMICS AND

WINDTUNNELS

AERODYNAMICS & WINDTUNNELS

InnSol, Inc. AERODYNAMICS & WINDTUNNELS

AERODYNAMICS:

IS THE STUDY OF THE FORCES EXERTED BY

AIR OR OTHER GASES IN MOTION

DEFINITION



WHY SHOULD WE CARE ABOUT AERODYNAMICS?BECAUSE IT SIGNIFICANTLY AFFECTS THE PERFORMANCE & SAFETY OF MANY OF THE THINGS WE USE AND THINGS WE DO:

• AIRCRAFT • SPACECRAFT• AUTOMOBILES AND TRUCKS• ENGINES (Gas turbines, reciprocating engines, etc.)• AIR HANDLING SYSTEMS (fans, blowers, air conditioners, etc.)• BUILDINGS• WIND TURBINES• SPORTS (Ski jumping, speed skating, bicycle racing, windsurfing,

yacht racing, etc.)

DESIGN APPLICATIONS



AERO DESIGN PROCESS

THE SCIENTIFIC METHOD:

FOR THEORY TO BECOME LAW IT MUST BE TESTABLE

(otherwise it’s philosophy)

DEVELOP A PHYSICAL

DESIGN

PREDICT PERFORMANCE

AND BUILD A PROTOTYPE

TEST THE PROTOTYPE

CREATE AN ANALYTICAL

MODEL(DESIGN AND

ANALYSIS)

DO THE RESULTS MATCH THE

PREDICTION?

NO

UPDATE THE ANALYTICAL

MODEL

UPDATE THE PROTOTYPE

CELEBRATE

DESCRIBE THE

PROBLEM

YES

THE WIND TUNNEL IS THE PRIMARY

TEST VEHICLE FOR AERODYNAMIC DESIGN



UNDERSTANDING AERODYNAMICS

• CONSERVATION OF ENERGY • NEWTON’S THIRD LAW OF MOTION• POTENTIAL & KINETIC ENERGY• CONTINUITY EQUATION

GOVERNING LAWS OF PHYSICS



THE LAW OF CONSERVATION OF ENERGY

• energy can neither be created nor destroyed, but only changed from one form into another or transferred from one object to another

• the total amount of energy in a closed system remains constant

ENERGY



NEWTONS THIRD LAW

• FOR EVERY ACTION THERE IS AN (OPPOSED) EQUAL AND OPPOSITE REACTION

LAWS OF MOTION



POTENTIAL ENERGYPE = mass x g x height = weight x height

KINETIC ENERGYKE = ½ mass x velocity2 = weight x velocity2

2g

ENERGY TRANSFORMATION



THE FORCES EXERTED BY AIR ARE MANIFEST IN PRESSURE

DEFINITION



FLOW THROUGH A CONSTRAINED REGION

Continuity EquationW1 = W2 = Wn

flow = density x area x velocityW = d x A x V

CONTINUITY EQUATION

1 2n



STATIC PRESSURE

THE CONCEPT OF PRESSURE

V = 0

OBSERVER MOVING WITH THE AIR



• DYNAMIC (TOTAL) PRESSURE• Pressure due to velocity of air relative to the velocity of the

object


OBSERVER MOVING WITH THE OBJECT



RELATIONSHIP BETWEEN STATIC AND TOTAL PRESSURE


Total Temp ≈ Static Temp x (1 + c x V2) Total Press ≈ Static Press x (1 + c x V2)3.5

Total Press ≈ Static Press x (Total/Static Temp)3.5



AERODYNAMICS OF WINGS

DEFINITION



VELOCITY IS GOVERNED BY THE CONTINUITY EQUATION • Density (d) varies with T & P• T & P remain constant unless heat and/or work is added or removed

(conservation of energy), thus d = constant• Therefore: W = constant = d x A x V = constant x A x V• Thus V varies only with A (V = constant/A)

VELOCITY IN A CONSTRAINED SPACE



FLOW OVER A WING




PRESSURE DISTRIBUTION AROUND A WING




C




ANGLE OF ATTACK


As the angle of attack increases lift increases but so does drag

At some point the air cannot follow the wing surface and separates. This causes the wing to rapidly lose lift, creating stall



AERODYNAMIC FORCES ON A WING




AERODYNAMIC & PHYSICAL LOADS ON AN AIRCRAFT

AERODYNAMIC LOADS



LIFT AND DRAG




WINDTUNNELS ARE USED TO:• DEVELOP EMPIRICAL DESIGN DATA (eg Lift/Drag polars)• INVESTIGATE AERODYNAMIC PHENOMENA (eg flutter)• DEVELOP AND VERIFY DESIGNS

WIND TUNNELS



WRIGHT BROTHERS WIND TUNNEL

WINDTUNNELS

Critical to the Wright Brothers’ success was

their wind tunnel. When they tested their

previous design that failed expectations they

discovered that its lift was 1/3 of design

predictions



WRIGHT BROTHERS WIND TUNNEL

WINDTUNNELS



LARGE SCALE WIND TUNNELS

WINDTUNNELS



OPTIONS

WINDTUNNELS

CLOSED LOOP:Facilitates changes in altitude (pressure).Reduces energy consumption.

OPEN LOOP:Required for engine testing and testing with inlet additives (eg water, contamination, etc.• Ambient• Inlet air heaters & coolers• Exhaust pumps to vary altitude

and flight speed.

BLOW DOWN :• Open configuration• Closed configuration



BLOW DOWN WIND TUNNELS

WINDTUNNELS



SCHLIEREN , SHADOW GRAPHS, & LDVUSE AIR DENSITY FOR VISUALIZATION

VISUALIZING FLOW FIELDS



VERTICAL WIND TUNNELS

WINDTUNNELS

NASA LEWIS (GLENN) 5 FT VERTICAL WIND TUNNEL - 1917



NON - AIRCRAFT APPLICATIONS

WINDTUNNELS



AERODYNAMIC DRAG MEASUREMENT ON BUILDINGS USING SCALE MODELS

WINDTUNNELS



WIND LOADS ON STRUCTURES

HURRICANES & TORNADOS



0

HURRICANES AND TORNADOES

EFFECT OF HIGHWIND SPEED ON

HOUSE ROOF LOADS

Wind Speed mph 100 150 200 250 300Wind Speed ft/s 147 220 293 367 440Roof Area sq ft 2000 2000 2000 2000 2000Mach # 0.1311 0.1966 0.2621 0.3277 0.3932Total Pressure lb/sq in 14.70 14.70 14.70 14.70 14.70Static Pressure lb/sq in 14.52 14.31 14.01 13.65 13.21Press Difference lb/sq in 0.18 0.39 0.69 1.05 1.49Tot/Stat Press 1.012 1.027 1.049 1.077 1.112Load on Roof tons 25.3 56.3 98.8 151.7 214.0



AERODYNAMICS OF VEHICLES

OBJECTIVE: REDUCE DRAG FOR REDUCED FUEL CONSUMPTION AND INCREASED SPEED.

• AUTOMOBILES, • RACE CARS, • MOTORCYCLES & • TRUCKS

WINDTUNNELS



AUTOMOTIVE APPLICATIONS

GM WIND TUNNEL

MERCEDES BENZ ENVIRONMENTAL

TESTING

NASA LANGLEY

FULL SCALE TESTING



SMOKE STREAMS

FLOW VISUALIZATION

Smoke streams

clearly show flow

separation and

turbulence – which means higher drag and higher

fuel consumption



HOW TO PREVENT A CAR FROM BECOMING AN AIRPLANE

FLOW VISUALIZATION

INVERTED WING

SPOILER



WOOL TUFTS

FLOW VISUALIZATION



• SKI JUMPING• DOWNHILL RACING• SPEED SKATING• SKY DIVING • BICYCLE RACING• GOLF

AERODYNAMICS IN SPORTS



SKI JUMPING

WINDTUNNELS

V STYLE

CLASSIC STYLE



SKY DIVING

WINDTUNNELS

MODERN VERTICAL WIND TUNNELS – FOR

FUN AND GAMES



RACING APPLICATIONS

WINDTUNNELS



WHY DIMPLED GOLFBALLS?

AERODYNAMICS OF GOLF

In the early days of golf when the balls were smooth some golfers

noticed that their old beat up golf balls drove further than new golf

balls – hence the design of dimpled ball covers.



AERODYNAMICS OF SPEED SKATING

Under Armour and Lockheed Martin designed gear for the 2014 Winter Olympics



THE LEADER FIGHTS THE HIGHEST DRAG

AERODYNAMICS OF DRAFTING

PEDALING A BICYCLE AT 152

MPH



• EVERYONE IN ONE WAY OR ANOTHER IS AFFECTED BY AERODYNAMICS (BUT MOST OF US DO NOT REALIZE IT)

• THE PHENOMENAE OF AERODYNAMICS AND THE ATTENDANT LAWS OF PHYSICS CAN BE DEMONSTRATED WITH A SIMPLE WIND TUNNEL

• ITS ADVANTAGE IS THAT IT PROVIDES AN INTERESTING “SEE AND TOUCH” APPROACH WITH CONSIDERABLE OPTIONS FOR STUDENTS TO DEVELOP AN UNDERSTANDING OF BASIC SCIENCE

AERODYNAMICS



Dennis Barbeau [email protected]

AERODYNAMICS

Documents

AERODYNAMICS AND WINDTUNNELS