l8 research areas of aeroelasticity

8/10/2019 L8 Research Areas of Aeroelasticity

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8th Research Areas ofAeroelasticity

Xie Changchuan2014 Autumn


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Content1Aeroelasticity of complete aircraft

2Aeroservoelasticity

3Techniques in aeroelastic test4Aeroelasticity of very flexible aircraft

5Aeroelastic tailoring

6Aeroservoelasticity

Main AimsRealize thejobs in aeroelastic design and

analysis which have not taught in this lesson.Furthermore, some new research areas and

state of arts.


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Modern flight dynamics/aeroelasticity

Aeroelasticity of complete aircraft

Frequency range of

rigid movements

Frequency

difference

The highest frequency

of rigid movement

The lowest frequency of

elastic vibration

Frequency

Frequency range of

elastic vibrations

Frequency range of fight control


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Movement equations of

Rigid/Elastic couplingconsider together:

freedoms of rigid motion

freedoms of elastic motion

Problemshow to deal with the

inertial and aerodynamic

coupling between these two

kinds of freedoms?

Equilibrium equations

of static aeroelastici tyProblems: how to solve them

when structure is deformed?

Small disturbance equation

state space model

Problems: how to calculate the

unsteady aerodynamics with

rigid/elastic coupling?

Solution of full motion

equations in time domain

Flight dynamic

equations

Trim analysis

Control and

stability analysis

Design of

control law

Flight simulation

Modern flight dynamics/aeroelasticity


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State of arts theory of f light dynamics of elastic aircraft

1960s, Dusto introduced the method of influence

coefficient to solve the stability problem of elastic

aircraft

Rough description to

structure and aerodynamics

1980s, Rodden established equations of quasi-

steady flight for elastic aircraft, to solve the divergence,

trim and flight load distribution, etc.

Can not give out

dynamic analysis

later in 1980s, Waszak and Schmidt establishedequations by energy method for elastic aircraft flight

with the mean axes, including the rigid and elastic

mode simultaneously.

The aerodynamics aresimple (quasi-steady theory)

2000s, Meirovitch and Tuzcu established rigid-

elastic coupled state equations based on quasi-coordinate theory in multi-body dynamics, to deal with

stability and control response of elastic aircraft.

Complicated equations

The aerodynamics are

simple (strip theory)


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Equations motion of motion ofrigid aircraft (flat irrotational earth)

| ( | ) |V VI I I Aero Prop

d d dm m m

dt dt dt = = + +

p Vg F F

I earth frame, inertial coordinates

( ).

. .|V I

V I V I V I Aero Prop

Vol

d

dVdt

+ = +

p p

p M M

|VI V V V V

dU V W

dt= + +

pV i j k V V Vx y z= + +p i j k

x V y V z Vg g g= + +g i j k .I V V V VP Q R= + + i j k

Aero Ax V Ay V Az VF F F= + +F i j k Prop Px V Py V Pz V F F F= + +F i j k

Aero A V A V A VL M N= + +M i j k Prop P V P V P V L M N= + +M i j k

From these relations above, the equations can be written as

scalar form

Vector form

V body-fixed frame, noninertial coordinates


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Aeroelasticity of complete aircraft

D. K. Schimidt, Modern Flight Dynamics, McGraw Hill, New York, 2012

Full motion

Nonlinear

Equations

Nonlinear reference equations

Solve a certain fl ight state

Linear disturbed equationsStability, flight/control derivatives

Rigid/elastic modes

Small motion/deformation response

Equations motion of motion forelastic aircraft (flat irrotational earth)


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Aeroservoelasticity

Tetrahedron of aeroservoelasticity

A aerodynamics E elastic forces

I inertial forces S control forces

S

EI

W2

xs

Motion singnal transformation

Elastic aircraft Mode parameters

Servo actuator Servo system Auto control system Sensors

s

W1W3W4

q

xi

Structural feedback loop

Structural feedback control loop


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Equation of aeroservoelasticity

s s s s s s s sq q + + = +M q C q K q A q M A

Output of

overload factor

12 2( ) ( )s s s s s

s s s q s q s

= + + + q M C K A M A

Frequency domain method, Laplace transform

2 2

( ) ( ) ( ) ( ) ( ) ( )s s s s s s s ss s s s s q s s s q s + + = +M q C q K q A q M A

1z s

g= =n Fq

Output transform 21( ) ( )ss s sg=

y Fq

Transfer function

12 2 21

( )s s s s ss s s s q s qg

= + + + G F M C K A M A


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Time domain method, state space model

= +

= +

x Ax Bu

Cx Du

Note: most unsteady aerodynamics calculations are in

frequency domain. They should be fitted in time domain.The analysis methods forSISO and MIMO are different.

Research work: stability of aeroservoelasticity (servo flutter)

flutter suppression, gust alleviation

maneuver load alleviation, flight simulation

Equation of aeroservoelasticity


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Gust response and alleviation of large aspect ratio wing

Gust generator The wing has innerand outercontrol

surfaces on trailing edge


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Support system

Has freedoms of pitching

and plunging

Wind tunnel test

Gust response and alleviation of elastic aircraft


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Aeroelastic test

Types of test

Stiffness test of components

GVT of components

Wind tunnel test of componentsScaled complete aircraft wind

tunnel test

GVT of complete aircraft

Servoelastic test of complete aircraftFlight test

Overall design

Researching test

Empirical formula

Simplified calculation

Parts & componentsdesi n

Flutter test model,Stiffness & GVT,

Flutter tesr

Normal modes

Flutter analysisVerified by test

Prototype ofaircraft

Stiffness & GVT

Model test in doubt case

Update model

Flutter analysis to eliminateroblems in calculation

Limitations to flight

Flight vibration& flutter test

Dynamic response calculationverified by flight test

Solve the problemsin flight test

Prototype verified

Jobs in aeroelastic design


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Relationship of normal modes test, dynamic analysis and

structure design


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Model design and GVT system

Typical scaled model of

large aspect ratio wing

GVT system

Similarity law

of mechanics

Geometry

Stiffness Mass


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HeliosGlobal eagle

Typical long endurance UAV

Geometrical nonlinear flight dynamics/aeroelasticity

Aeroelasticity of very flexible aircraft


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Cruise stateCruise state, vertical, vertical

displacement is about 3.6mdisplacement is about 3.6m

Ground stateGround state, the wing has no, the wing has no

much bendingmuch bending

Maximum load stateMaximum load state, vertical

displacement is about 7.9m

TheThe deformationdeformation will be morewill be moresignificantsignificant adoptingadopting compositecomposite

materialmaterial than metallic materialthan metallic material

Boeing 787Boeing 787

Wing span almost 60m


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ChartChart 1818


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State of artUSA Michigan Universitysmart structure and aeroelastic Lab

Prof. Cesnik one of the first researchers on geometrical aeroelasticity

of fixed wing aircraft

Projects: HALEX-HALE NASA, Boeing, US air force supportingfunding sum beyond 10 million US dollars

Alabama Universitygroup of aeroelasticity and flight simulation

flight simulation platform of very flexible aircraft

UK Bristol Universitynonlinearity and aeroelasticity Lab

Prof. Cooper large deformation of joint-wing NASA supporting

aeroelasticity and design of large deformed wing and complete aircraft

Airbus supportingfunding sum beyond 8 million US dollars

Imperial Collegegroup on dynamics and aeroelasticity

Royal aeronautical society supporting

Prof. Palacios geometrical nonlinear flight dynamics and aeroelasticityconstructed software SHARP


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Aeroelasticity Lab in Beihang Univ. (My work)

Nonlinear static aeroelasticity and flutterof very flexible wing

Nonlinear flight load and flutterof very flexible complete aircraft

GVT and wind tunnel test of large deformed wing

Fixed

end

Wing Beam Wing FrameMid of slender

tube

After cone

Front cone

Fuselage

Wingtip storeCG

Wing spar

All-removableHorizontal tail

Rotational axis

Aileron


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Engineering applications

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0

10

20

30

40

50

60

70

80

90

100

110

120

130

140

150

VF

/V*

Load Scale

Stable margin

Load condition


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Aeroelastic tailoring

Optimization

problem

Steady aeroelastic trimflutter analysis

N

Define the optimizestrategy and parameters

Generate initial population P(t)(structural and contro l variables)

Individual fitnessassessment

Convergence

condition

Generate new population P(t+1)

End

P(t)

P(t+1)Y

min F (v)

cnj = 1,

dni = 1,

s.t. 1( )( )( )

F

Fg

F=

vv

v

2 21

1

( )( ) ( ) ( )

tn

i

i i

FF v

v=

=

v

v

1

( )( ) 0

tnj

j i

i i

gg v

v=

+

vv

lower upper ( ) ( )i i i i iv v v v v+


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Footholdsyntheses design of structure, aerodynamics

and control law

Aeroelastictailoring/design

Aeroelastic solver

Optimize method

The law of design parameters on aircraft performance

The requirements of large-scale optimization on

aeroelastic solver The patterns of MDO strategy and variables selection

The methods of MD coupling and rapid solving

The choice and hybrid of optimizing methods

Aeroelastic tailoring


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Aerothermoelasticity

The coupling relationships

of aerothermoelasticity

Aerothermoelasticmodel based on 2

way coupling

Aerodynamic

heating

Heat

conduction

Aerothermal

Aerodynamics Elasticdeformation

Inertial

1

aeroelasticity

2


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Coupl ing calculation of aerodynamic

heating and aeroelasticity

Aerothermoelasticity

Aerodynamicheating and

conduction

Aeroelasticity

t

t +tAT

tAT

tAE

t +2tAT

UpdatedT

field

UpdatedT

field

UpdatedT

field

Updated

flowp

Updated

flowp

Updated

flowp


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Any adviceson this course

END

Thank you

l8 research areas of aeroelasticity

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