Aerodynamics Recent Developements

7/28/2019 Aerodynamics Recent Developements

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DEVELOPMENTS IN APPLIED AERODYNAMICS AND

FLIGHT MECHANICS OF UNMANNED AERIAL VEHICLESby

Dominic D. J. Chandar, Mark Leon C.S. Tan and M. Damodaran

Dr. Murali Damodaran

Associate ProfessorSchool of Mechanical and Aerospace Engineering

Nanyang Technological University

5 APRIL 2008

presented by

5- 6 April 2008,

Indian Institute of Technology, Kanpur

INDIA

2nd Joint Workshop in

Mechanical, Aerospace and Industrial

and Management Engineering


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FIXED WING

ROTARY WING/DUCTED FAN

FLAPPING WING

MORPHED CONFIGURATIONS

Unmanned Aerial Vehicles


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OVERVIEW

1. CFD Simulation of Low Reynolds NumberFlapping Wing Aerodynamics

- with Dominic

2. Integrated Computational Framework for

Aerodynamics, Flight mechanics and Control

of Fixed Wing UAVs.

- Mark Leon Tan C S


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Overture / OverBlownOverture / OverBlown

Overture Framework

Overset

Moving

grids

Overset Flow

Solver (Over-Blown)

Parallel

Computing on

Stationary

Grids A++ Framework

Faster ArrayManipulation

InterfaceWith

PETSc

DeformingBody Motion with

GCL

(Added Recently)


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LOW REYNOLDS NUMBER FLAPPING WING

AERODYNAMICS MODELING


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OVERLAPPING / COMPOSITE / OVERSET / CHIMERA MESH

Individual Component Meshes

generated independently

Ogen MeshOgen Mesh

GeneratorGenerator

LOW REYNOLDS NUMBER FLAPPING WINGAERODYNAMICS MODELING


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INTERPOLATION BETWEEN MESHES

EXPLICIT

IMPLICIT

SOLUTION AT INTERPOLATION POINTS IS OBTAINED FROM

DISCRETIZATION POINTS OF NEIGHBORING GRID

SOLUTION AT INTERPOLATION POINTS IS OBTAINED FROM

INTERPOLATION & DISCRETIZATION POINTS OF

NEIGHBORING GRID


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Interpolation Weights

For 2nd order Scheme : Width of

Interpolation = 3 (Quadratic)

U(i,j)

In 1D

Width of discretization = Width of Interpolation

If Overlap ~ Constant x MeshSize : Width of Interpolation = 2pr + 1

2p = Order of PDE, 2r = Order of Discretization


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Vortex On The Interpolation Boundary

Chandar and Damodaran, AIAA J, Vol 46, No2, 2008, pp 429-438


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x = G (r,t)

INTERPOLATION ON DYNAMIC MESHES

NO REMESHING

ONLY INTERPOLATION POINTS CHANGE

RIGID BODY MOTION

How About Deforming Bodies ?


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DEFORMING WING

Hyperbolic mesh generation at each timestep.

Marching distance from the boundary

limited to a small radius

Jacobian at each deforming point follows

the Geometric Conservation Law (ONLY

for the mesh surrounding the wing)

0J

J J Jt t t t

+ + + =

J = Jacobian of the transformation x=x(,, ) ;

,, are Computational Coordinates

Deforming Wing -Video


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DEFORMING WING

Hyperbolic mesh generation at each time

step.

Marching distance from the boundary

limited to a small radius

Jacobian at each deforming point follows

the Geometric Conservation Law (ONLY

for the mesh surrounding the wing)


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Prescribed motion (Active flight).

Motion determined from the forces (Passive Flight)

Weakly Coupled Navier-Stokes- Newtons Law

x=x0sin(2ft),

=0sin(2ft)

,A i i k ki

d

F pn n dS

= ( )cmd

T r x dF

= 2

2

cmA

d xF

dt

dJ Tdt

=

= , i i iJ I e=

Ti i iI e = i ie e=

OrientationOrientation

PositionPosition

LOW REYNOLDS NUMBER FLAPPING WINGAERODYNAMICS MODELING


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Unsteady Low Reynolds NumberUnsteady Low Reynolds Number

Flow ProblemsFlow Problems Coupling With 6DOF ModelCoupling With 6DOF Model

Free Flight of a Flapping Wing

Fluttering / Tumbling of Cards

Reverse Hysteresis Effects

Numerical computations aid in analyzing

The key parameters responsible for

Flutter / Tumble of a Falling Card

The onset of Forward Flight due to Flapping

Can be determined

Can Lift drop with increase in

Angle of attack ?? Computations do reveal

This fact for pitching above certain

frequencies


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Fluttering and Tumbling of Cards

Falling Rectangular Card

Re = 630

Aspect Ratio = 2

Trajectory

Angles ~ ei . ei

e1

e2

e3

e1

e2

e3


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x

yz

Y-Vorticity X-Z Plane

Z-Vorticity Z-Vorticity

Vorticity Magnitude


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Free fall of a Rectangular card Wang, J ( 2005 )Free fall of a Rectangular card Wang, J ( 2005 )

70cm

45 cm

30 cm

L = 0.648 cm h = 0.081 cm

w = 19 cmRe = 837

Mesh ~ 512 x 256


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Trajectory

Fx

Fy

Streamlines

Vorticity

Free fall of a Rectangular card Wang, J ( 2005 )Free fall of a Rectangular card Wang, J ( 2005 )


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Autorotation / Flutter of Rectangular PlatesAutorotation / Flutter of Rectangular Plates

Pinned at the centre of mass

Inflow

( )* 21 112

b

f

I

= +Non-dimensional Moment of Inertia

Density of plate / Density of fluid

Thickness to chord ratio


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0.1= 0.5=

1.0=

log (|vorticity|)

vorticity


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A pinned card excited by aerodynamic forces will

attain any one of the three states of motion

High density and large thickness high inertia

rotates slowly

For low frequency oscillations, frequency of vortex

shedding is greater than frequency of rotation

For high frequency oscillations, frequency of vortexshedding is less than the frequency of rotation.


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0.2= 0.5=

Comparison with the numerical results of Mittal.R et al (2004)

Lift Coefficient

Not Flutter as pointed out by Mittal et.al but a state of low frequency / amplitude#oscillation

#Chandar and Damodaran, Unsteady Low Reynolds Number Aerodynamics of Flapping,

Fluttering and Tumbling, AIAA J In Review


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Autorotation / Flutter of Elliptical PlatesAutorotation / Flutter of Elliptical Plates

Comparison with the numerical results of Lugt (1981) : Forced Rotation

Moment coefficient for different Reduced frequencies (k)

K = 0.167 K = 0.25

K = 0.5 K = 1.0


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FREE-FLIGHT OF A FLAPPING WINGFREE-FLIGHT OF A FLAPPING WING

Mass = 1.207

Aspect Ratio = 2.0

Re = O(100)

t/c = 10 %

Frequency f= 1.5 Hz

0

01

sin(2 ) 0,1, 2

0

,k k kf t k

= =

=

Flap for One cycle with Centre of mass fixed then let it freeFlap for One cycle with Centre of mass fixed then let it free

x

y

z


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VORTICITY FIELDSVORTICITY FIELDS

X- Vorticity

Z- Vorticity Vorticity Magnitude


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Thrust over One CycleThrust over One Cycle

A

B

C D

E

Thrust Angular position of wing


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Trajectory and Forward SpeedTrajectory and Forward Speed

Position of centre of mass Forward speed


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Wing in Constant Speed Rotation after a Fast StartWing in Constant Speed Rotation after a Fast Start

x

y

z

Re = 100

Aspect Ratio = 2

t/c = 0.12

0

0

0.5 (1 cos( )), 0 1

1

,

t t

t

=

= >

Lan and Sun (2001)

Dickinson et. al (1999)


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Volume meshes on wing tip caps


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+ OverBlown -102,600 points (coarse~ Wing + wing caps)

* Lan and Sun (2001) 359,055 points

CL (OverBlown) = 1.08

CL (Lan and Sun) = 1.00

CD (OverBlown) = 1.06

CD (Lan and Sun) = 1.01Steady

State


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Recent Developments - Deforming Airfoil ComputationsRecent Developments - Deforming Airfoil Computations

Development of an Interface to

Visualize Deforming Body

Problems


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Deforming Motion Class - ValidationDeforming Motion Class - Validation

( , ) ( ) sin( ) sin( )0

py x t y x Ax t kx B t = + + + +

Initial Profile Wave-like profile Rigid translation

RIGID BODY PLUNGING USING THE

DEFORMING BODY CLASS

A = 0, B = 0.4, = 2, Re = 10,000


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Deforming Airfoil ComputationsDeforming Airfoil Computations

( , ) ( ) sin( ) sin( )0

py x t y x Ax t kx B t = + + + +

A = 0.1, p =2, k =0, = /2, B =1 A = 0.3, p =2, k =0, = /2, B =1

A = 0.2, p =3, k =1, = 0, B =0

Filament-like flapping

Re = 10000

Re = 1000


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Deforming Airfoil ComputationsDeforming Airfoil Computations

Two Filaments deforming


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Integrated FlightDynamics Model of

a UAV


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Overview of Flight Dynamics and ControlOverview of Flight Dynamics and Control

Develop Integrated Computational Model to:

Address the Stability and Control Problem

Assist in Formulation of Flight Control Law

Use CFD to generate unavailable UAV aerodynamic data andto provide a basis for developing control law

Estimate unavailable UAV stability and control derivatives

Analyze impact of various flight control systems tomitigate the flight stability problem


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Integrated Computational Framework for Aerodynamics,Integrated Computational Framework for Aerodynamics,Flight Dynamics and Control ofFlight Dynamics and Control ofUAVsUAVs

Simulate Using Matlab/Simulink

drivenAerospace Blockset/AeroSim

MINDEF RSAF Air Logs

DSTA Funded Project@NTU

July 2005-July 2007


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Flight Dynamics ModelFlight Dynamics Model

Simulate Using Matlab/Simulink driven Aerospace Blockset/AeroSim


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Design of Dutch Roll Damper Dutch roll damper

Suppress the natural dynamics of the dutch roll

To desensitize the overall damping to the variation of flightparameters

Provide damping with respect to inertia space

r

a

0 +

-

u

BuAxx +=

Plant

C

ks

s

+

Aircraft

Dynamics

Dutch Roll

Damper

Open LoopAnalysis

Obtain desired

freq & damping

Close loop

analysis

Modification of

System

Design Cycle


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Design of Dutch Roll Damper

r

a

0 +

-

u

BuAxx +=

Plant

C

Need to obtain

the gain for the

feedback loop

Aircraft Dynamics

Rudder ControlSurface as the

key controller

Yaw Rate output

Dutch Roll

Damper


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Flight Dynamics ModelFlight Dynamics Model Simulation inSimulation in FlightGearFlightGear


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CONCLUDING REMARKS

CFD Simulation of Low Reynolds Number Aerodynamics of Flapping

Wing, Tumbling and Fluttering Plates etc.

Coupling of Structural Dynamics and CFD to model flexible flapping

wings the next step.

Integrated Framework to be developed to include rotary wing and

flapping wing MAVs/UAVs


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THANKTHANK

YOUYOU

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Aerodynamics Recent Developements