research overview and cognitive...

1/29/2013

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Research overview and cognitive approaches

Partha P. Sarkar, Ph.D.Professor

WESEP 594

January 24, 2013

1

• My Background

• My Research Overview and Approach

• My Perspectives

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My Background

Education:• Ph.D., Johns Hopkins University, 1989-1992

• M.S., Washington State University, 1985-1986

• B.Tech, Indian Institute of Technology (Kanpur), 1980-1985

Academic Experience (20 yrs+):• Texas Tech University, 1992-2000

• Iowa State University, 2000-present

Industrial Experience (2 yrs):• Structural Engineering Research Center (SERC), Chennai, India, 1988-89

• DCPL (Kuljian Corporation, USA), Mumbai, India, 1987-88

3

Professional Highlights• TA Wilson Endowed Chair in Engineering, 2000-2008

• Guest Professor, 2008-2012, Global Center of Excellence on Wind Engineering, Tokyo Polytechnic University, Atsugi, Japan

• Invited talk to US Congressional Staff, 2005

• President, American Assoc. for Wind Engineering (2011-12)

• Member, Ed. Board, J. of Wind Engr. and Ind. Aero. & 2 Other Journals

• Appearance on several National/Intl.TV Channels, Museum, Public Radio

Research Interests

Wind Engineering/Wind Energy • Wind-tunnel and full-scale testing of CE structures

• Aerodynamics of flexible structures

• Wind loads on low-rise buildings/structures

• Design of next generation wind tunnels

• Study of tornado-, microburst-, gust front-induced wind loads 4

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Research Highlights

Sponsors: Federal - NSF, NOAA, NAVY, DOE, State - TxDOT, IAWIND, Industry

Projects: 40+ projects with a total budget of +16.5M

Students: Advised 4 postdocs, 11 PhD (8 graduated), 13 MS, 50+ undergrads

Publications: +125 articles (~50 Journal Papers), 3 Proceedings (Ed), 1 CD-

ROM, 4 Patents

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Faculty CollaboratorsDr. Vinay Dayal, Associate Professor of Aerospace Engineering

Dr. William A. Gallus, Jr., Professor of Geological and Atmo. Sciences

Dr. Matt Frank, Associate Professor of Industrial Engineering

Dr. Hui Hu, Associate Professor of Aerospace Engineering

Dr. Atul Kelkar, Professor of Mechanical Engineering

Dr. Mike Olsen, Professor of Mechanical Engineering

Dr. Brent Phares, Assoc. Director, Bridge Engineering Center

Dr. Sri Sritharan, Professor of Civil Engineering

Dr. Gene Takle, Professor of Agronomy

Dr. Terry Wipf, Professor/Chair of Civil Engineering (Director, Bridge Engineering

Center)

Dr. Fred L. Haan, Associate Professor of Mech. Engineering, Rose-Hulman Institute

Tim Samaras, Denver, Colorado

Dr. Joshua Wurman, Principal, CSWR, Colorado

and others …6

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It is a team effort

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ASEE: Prism Nov. 2006

WESEPResearch Interests

• Studying wind flow characteristics and interference loading effects in wind farms

• Prediction of aerodynamic/aeroelastic loads and response of wind turbine components

• SHM and fatigue life prediction

• Developing of wind energy capturing systems

Curriculum Development

WESEP 511 Wind Energy System Design Advanced design and control of horizontal-axis wind turbines which include design loads, component design and prediction of its residual life, design of wind farms, electro-mechanical energy conversion systems, and control system and its implementation.

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Current/Pending Wind Energy Projects

• IGERT-WESEP with Jim McCalley (PI), NSF

• Characterization of Surface Wind Energy Resources and Wake Interferences among Wind Turbines over Complex Terrains for Optimal Site Design and Turbine Durability –with Dr. Hui Hu (PI), 01/01/2012 to12/31/2014, NSF

• Innovative Offshore Vertical-Axis Wind Turbine Rotors –with Dr. Matt Frank (PI), 01/01/2012 to 12/31/2016, DOE

• Smart Sensory Membrane for Wind Turbine Blades –with Dr. Simon Laflamme (PI), pending, Iowa Energy Center

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Damage to Infrastructure

Every year on an average in the US: $6.3 billion worth of wind damage including

$1 billion worth of damage from tornadoes $1.4 billion worth of damage from microburst

36% of property losses from major natural disasters is from wind

Every once in a while in the US: Hurricane damage exceeds $50 billion annually Metropolitan cities take a hit from tornadoes

e.g. Fort Worth, Texas – March 28, 2000

Wind Simulation and Testing Laboratory

US Losses (Rand Report)

Wild Fire12%

Others8% Flood

18%

Wind36%

Earthquake26%

2004, Hurricane Damage, Tampa

1992, Hurricane Damage, Miami

2000, Tornado Damage, Ft. Worth

1997, Rain-Wind Induced Fatigue Damage, Houston

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ISU Wind Engineering and Experimental Aerodynamics (WEEA) Program

Wind engineering efforts seek to understandand mitigate the damaging effects of wind on:

•Built structures•Environment•People

Experimental aerodynamics efforts investigatebasic aerodynamic problems in:

•Aerospace•Agriculture•Environment•Transportation•Sports•Wind Energy

Meteorology

Statistics/Probability

Aerodynamics/Aeroelasticity

Structures

Materials

Vibrations


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Extreme wind events involve a wide range of complex flow patterns • Gust Front: violent gusting, direction change• Tornado: rotating flow, downdraft and updraft• Microburst: downdraft and outflow

Extreme Events are Transient in Nature


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• My Background


• My Perspectives

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Develop Facilities and Tools

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AABL Wind and Gust Tunnel• Two test sections

•Aero: 8 ft x 6 ft, 110 mph (<0.2% turbulence) and •ABL: 8 ft x 7.5 ft, 90 mph (various terrains)

• Gust generation: up to 25% change in wind speed in 4sec.

Aero: 8 ft x 6 ft, 110 mph

Gust Generator

Wind Simulation and Testing (WiST) Lab FacilitiesAtmospheric Boundary Layer (ABL) Simulation

8 ft x 7.25 ft, 110 mph15

Bypass Duct for Gust Generation

0.80

0.90

1.00

1.10

1.20

1.30

1.40

-4 -2 0 2 4 6 8 10 12

Time (sec)

Vel

ocit

y (V

/Vin

itia

l)

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• This facility was designed specifically to study tornado- and microburst-

induced forces on buildings and structures.

• Maximum diameter of tornado: 3.5 ft

• Maximum tangential velocity at 2/3rd fan Power: 14.5 m/s (32.4 mph)

• Maximum diameter of microburst: 6.0 ft

• Maximum downdraft or microburst velocity: 50 ft/sec (34 mph)

• Maximum translating wind speed: 0.61 ft/sec

Wind Simulation and Testing (WiST) Lab FacilitiesTornado or Microburst Wind Simulation

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Tornado/Microburst Simulator

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4 to 8 ft

Fan Motor

5.5 m (18 ft)

1.83 m (6 ft)

0.3 m (1 ft)

1.52 m (5 ft)

H = 1 to 5 ft

Rotating downdraftAdjustable ground plane

Turning Vane Open

Honeycomb/Screen

Tornado Mode

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Wind Simulation and Testing (WiST) Lab FacilitiesWind-Induced Vibration

Suspension system for studying aeroelastic (e.g. flutter, vortex shedding, buffeting) problems 3 degrees of freedom

Free vibration or forced vibration

Bridge decks

Airfoils

Stay cables

Towers and poles

Vibration of structural systems

Aerospace Engineering

Contact: Prof. Partha Sarkar, AerE

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Modern Instruments: Fast, Accurate, Adequate

Instrumentation: Wind Tunnel

Vvert

VradVtan

18-hole Omniprobe for 3D velocity measurement

High-speed Digital Pressure Scanner DSA Series

Sonic Anemometer: Field Measurement

Particle Image Velocimetry Image

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• JR3 6-component force balance

• Scanivalve Zoc 64 ch pressure transducers– 500 samples per channel per second

• Constant temperature anemometry– 4 channels

• Cobra probe– 3D velocity measurements

• Laser-based Velocity Instruments– Stereoscopic PIV– LDA

• 3-D Router and Rapid Prototype Machine for Models

Wind Simulation and Testing (WiST) Lab FacilitiesInstrumentation

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ABL Simulation of Straight-Line Winds

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Fig.1 Miami-Ft Lauderdale

Fig. 2 Dallas

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Studying Effects of Tornadoes and Microburst

• Laboratory Simulations

• Field Measurements

• Numerical Simulations

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Types of tornados (National Geographic)

inflow

2max

inflow2)( Ratio Swirl

Q

rV

Q

rrS c

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Tangential Velocity Validation

Tangential velocity profiles for tornado simulator and field radar data for Spencer, South Dakota tornado of 1998 and Mulhall, Oklahoma tornado of 1999.

Doppler on WheelsJ. Wurman (2004,2005)

r/rc

v /v

ma

x

0 1 2 3 4

0

0.5

1Vane 5 (z=0.10rc)

Vane 5(z=0.24rc)

Vane 5 (z=0.38rc)

Vane 5 (z=0.52rc)

Mulhall radar (z=0.52rc)

Spencer radar (z=0.52rc)

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ISU Collaborative EffortTimothy M. Samaras

ISU Collaborative Effort

0 25 50 75 100 125 150 175 200 225 250840

855

870

885

900

915

930

945

960

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Instantaneous vortex structure at θv=15º, Low Swirl Ratio

Single-celled vortex

Zhang and Sarkar, 2011

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Instantaneous vortex structure at θv=45º, High Swirl Ratio

(a) Smooth ground (b) Rough ground IISub-vortices

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Hu, Yang, Sarkar, Haan (2011)

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-6 -4 -2 0 2 4 6-0.5

0

0.5

1

1.5

2

X/D

CF

z

R1:LS:0o

R1:HS:0o

R1:QS:0o

XY

Z

Wind Engineering ResearchTornado-Induced Wind Loads on Structures

by Haan, Sarkar, Gallus, Balaramudu (NSF Sponsored)

r/rc

v /v

ma

x

0 1 2 3 4

0

0.5

1Vane 5 (z=0.10rc)

Vane 5(z=0.24rc)

Vane 5 (z=0.38rc)

Vane 5 (z=0.52rc)

Mulhall radar (z=0.52rc)

Spencer radar (z=0.52rc)

Comparison of ISU Laboratory Simulated and Field Tornado Wind Speed Distributions

Transient Roof Uplift Load Coefficient for a Gable-Roofed Building in a Translating Tornado, LS-Low Speed, HS- High-Speed

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Results: Static Jet Microburst Simulation

(1) .... 2

11

b

z Cerf

n

b

zC

mU

U

C 1 =1.52, C2 =0.68, n=1/6.5

Cp

x/H

-1 -0.5 0 0.5 1

2

2.5

3

BA

CK

Cp

x/H

00.511.520

0.5

1

FR

ON

T

x/H

Cp

1.5-1.5

-1

-0.5

0

0.5k-esst k-wreazrngrsmlesExp

ROOF

U/Um

z/b

0 0.25 0.5 0.75 1 1.250

0.5

1

1.5

rakepivWoodRajarathnamEqn. (1)NIMROD Doppler Radar

Pressure Coefficients for Building at 1D from Center of the Jet

Comparison of Different Turbulence models with Experimental Data

Normalized Radial Velocity Profiles

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Results: Moving Jet Microburst Simulation

Jet Translation Speed1 = 0.225 m/sNozzle Jet Exit Velocity = 10 m/sNozzle Diameter = 203.2 mm (8 in.)

X/D

Cd

-3 -2 -1 0 1 2 3-2

-1.5

-1

-0.5

0

0.5

1

1.5

2S1 (CFD)S1 (Exp)

X /D

Cl

-3 -2 -1 0 1 2 3-1.5

-1

-0.5

0

0.5

1

1.5 S1 (CFD )S1 (Exp)

Drag coefficient for 25.4 mm cube Lift coefficient for 25.4 mm cube

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Model in ANSI/ANS4

0

2

1

14

57

N Jo

hn

son

St.

Flo

ren

ce S

t.

Lin

coln

St.

4th Ave.

3rd Ave.

4th

St.

3rd

St.

2n

d S

t.

1st S

t.

3rd Ave.

Conn St.

Sunset Dr.

Do

roth

y Ave

.

Ple

asa

nt D

r.

Ne

we

ll Ave

.

5th

St.

Circle Dr.

Hillto

p D

r.

N

42

2

2

2

4

2 22

32

4

224216

212436

1114

7

335376

2227

4 7

31

4

7

6

6

4

7

4

7

3 4 2 7

7

6

7

7

7

78

77

6888

6

667766

4

67

4 88 5

7

7

7 7 6 4 7

766

74 6 7 6

4

4

2

4

6

7

2

8 7

87878

7

4

6

42

2

1

2

86 7

7

1021

0

2

21

0

011

7 8 7

1

2

2

7

8

3

0 0 0

0

6 7

8

88

8

88

8

7

7

8

8

7

78

8

7

78

8

6

6

4

4

2

4

1 4

2

2

2

6

4

42

2

0

1

8

4

4 6

7

66

7

6

2

1

2

7

6 6

76

66

66

8

6

7

77

1 0

6

2

1

6433

6

No Damage（0）

DOD= 1,2

DOD= 3,4

DOD= 5,6

DOD= 7,8

DOD= 9,10

DOD= 9,10（Residence where there were the dead）

ElementarySchoolChur

ch Church

Bank A

High School

Warehouse

1

S Jo

hn

son

St.

57 14

57

14

IndustrialBuilding

6

6

Bank B

Fire EngineGarage

0 0

01

0

200m

Butler County

Des Moines

Iowa State

Parkersburg

0 100

An_l

An_r

As2_r

As2_l

As1_r

As1_l

Vt6

6

Tran

slation

Directio

n

Rm

0

Enhanced Fujita Scale

Field Investigation of EF5 Tornado Disaster in Parkersburg, IA, May 25, 2008, Kikitsu and Sarkar (2010)

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Field Investigation of EF5 Tornado Disaster in Parkersburg, IA, May 25, 2008 (Kikitsu and Sarkar, 2010)

High school Bank office

ResidenceTanks

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Thampi, Dayal and Sarkar, 2011

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Case 1 Vs Case 2

Deflection in global Z Deflection in global X Von Mises stress

• Case 1: X = -1.65rc (125 mph), Case 2: X = 0.25rc (180 mph) 40

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Final damage state of sealed building with roof uplift connectors designed for 40 m/s

(3-sec gust), with failed roof elements removed

Partially damaged example building at Parkersburg

Thampi, Dayal, Sarkar, 2011

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Time-domain modeling of loads

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A Time-Domain Model for Predicting Aerodynamic Loads on a Slender Support Structure for Fatigue Design

Chang, Phares and Sarkar, 2008

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Pole 1

Pull & release

0 2 4 6 8 100

100

200

300

400

500

6.40

3.33

1.300.31

Frequency (Hz)

Am

plit

ud

e

-200-100

0100200

0 2 4 6 8 10Frequency (Hz)

An

gle

(de

g)

Mode FEA FFT Difference Damping ratio

1 0.338 0.305 10.82% 0.25%

2 1.337 1.294 3.32% 0.17%

3 3.407 3.333 2.22% 0.29%

4 6.702 6.396 4.78% 0.27%

Long-Term Monitoring

Pluck test - Pole 1

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U(z)

X

Y

Z

)sin()(

)()1)((

2

1

cos)(sin)(

sin)(cos)(

22

2

12

tKCD

yKY

U

y

D

yKY

AUF

FFF

FFF

FFFFkyycym

FFFkxxcxm

L

yvs

LDy

b

LDx

b

yse

yvs

yb

y

xse

xb

x

Buffeting

Vortex shedding

Mathematical modelingEquation of motion

45

dU

vtC

U

utCAU

U

vn

U

vC

U

uCAU

d

dCC

d

dCCAuU

FFF

vLuD

t

LD

LL

DD

LDx

b

])(

)(')(

)('2[2

1

),()2

(2

1

])()[()(2

1

sin)(cos)(

0

2

2

2

dU

vtCC

U

utCAU

nU

vCC

U

uCAU

d

dCC

d

dCCAuU

FFF

vLDuL

t

LDL

LL

DD

LDy

b

])(

)(')()(

)('2[2

1

U

v ,)(])(

2[

2

1

)]()[()(2

1

cos)(sin)(

'

0

2

'2

2

0 t coefficienlift RMS :C

negligible ~ stiffness cAeroelasti:Y

tests tunnel windfrom - damping caeroelastiNonlinear :ε

tests tunnel windfrom - damping caeroelastiLinear :Y

)sin()(

)()1)((

2

1

L

2

1

22

2

12

tKC

D

yKY

U

y

D

yKY

AUF

L

yvs

Mathematical modelingBuffeting functions

Vortex shedding forcing function

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12-sided cylinder model

12 in. × 12 in. end plate with rounded corners

22-lb capacityForce transducer

Chain

0.75 in. Aluminum hollow rod

Coil Springs

Leaf spring

• Length: 20 in.

• Diameter: 4 in. (Corner to Corner)

Wind Tunnel TestingDynamic

• Mass: 0.19 slugs

• Frequency: 7.15 Hz

• Range of Re: 3.5×103 ~ 5.5×104 47

0 1 2 3 4 5-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Am

plit

ud

e,

y 0 (in

)

Time (sec)

0 1 2 3 4 5-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Am

plitu

de, y

0 (in

)

Time (sec)

0 1 2 3 4 5-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

Am

plitu

de,

y0 (

in)

Time (sec)

Before “Lock-in”

After “Lock-in”

“Lock-in”

0.0

0.5

1.0

1.5

2.0

0 1 2 3 4 5 6 7 8 9 10

Reduced velocity, U/nD

f s/f

n

“Lock-in”St =0.2

Wind Tunnel TestingDynamic: Strouhal number

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0.00

0.05

0.10

0.15

0.20

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Scruton number, Sc

Red

uced

am

plitu

de, y 0

/D

Experiment for a 12-sided cylinder

Fitted equation for a 12-sided cylinder

Griffin et al. for a circular cylinder

2.45c

2t

20

]SSπ(80.72[1

1.91

D

y

3.35c

2t

2

0

)]SSπ(80.43[1

1.29

D

y

Wind Tunnel TestingDynamic: Sc vs. Amplitude

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Aerodynamic Force ModelingComparison

S12

S10

U

0.0

2.5

5.0

7.5

10.0

0 5 10 15 20 25 30 35 40 45 501 min. mean wind speed (mph)

Stre

ss-R

ange

(ks

i) 1

S10

S12

0

2

4

6

8

0 5 10 15 20 25 30 35 40

1 min. mean wind speed (mph)

Stre

ss-r

ange

(ks

i) 1

±3·σ

X-Numerical Simuation

0

2

4

6

8

0 5 10 15 20 25 30 35 40

1 min. mean wind speed (mph)

Stre

ss-r

ange

(ks

i) 1

±3·σ

Y-Numerical Simuation

Peak

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Time-Domain Aeroelastic Loads and Response of Flexible Bridges in Gusty Wind: Prediction and Experimental Validation

Cao and Sarkar, 2012

Akashi Kaikyo Bridge

6532 ft. 51

Experimental Setup

View From Downstream View From Side

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Results and DiscussionStationary Wind Case

0

1

2

3

4

5

6

7

0 5 10 15 20

Vel

ocit

y, U

(m

/s)

Time (s)

53

Results and DiscussionStationary Wind Case

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0 5 10 15 20

Lif

t co

effi

cien

t, C

l

Time (s)

Numerical

Experimental

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0 5 10 15 20

Mom

ent

coef

fici

ent,

Cm

Time (s)

Numerical

Experimental

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-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0 5 10 15 20

Ver

tica

l dis

pla

cem

ent,

h

(m)

Time (s)

-5

-4

-3

-2

-1

0

1

2

3

4

0 5 10 15 20

Tor

sion

al d

isp

lace

men

t, α

(deg

)

Time (s)

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Mitigation of Wind Loads

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Understanding Wind Loads

EffectCause

Delta Wing Vortices on Roof

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Mitigation

Conical VortexDisrupter

Meteorological wind tunnel at CSU

-4

-2

0

2

0 100 200 300 400 500 600 700 800 900

Time t (sec)

Cp

-12

-10

-8

-6

-4

-2

0

2

Cp

Texas Tech WERFL

Mitigation

Before

After

Source: Sarkar, Wu, Banks and Meroney

Conical Vortex Disrupter Separated shear layer

Vortex

Wall

Building roof

Airflow inducedinto bubble

57

Aerodynamic Solutions to Cable Vibrations Sarkar, Mehta, Zhao, Gardner, Phelan

•

WIND

Upper Water Rivulet

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Full-scale tests for validation

Veteran’s Memorial Bridge, Port Arthur, TX

59

Full-scale tests for validation

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Full-scale tests for validationVeterans’ Memorial 5g cable-stay Vibration Event

61

Rain/wind-induced stay cable vibration

WIND

Upper Water Rivulet

Circular Ring

0

0.5

1

1.5

2

2.5

0 100 200 300 400

Reduced Velocity (=U/nD)

RM

S o

f D

ispl

. (in

.)

With UpperRivulet Only

With Rivulet andRings @ 2D

With Rivulet andRings @ 4D

Aerospace Engineering

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• My Background


• My Perspectives

63

Concept Phase

Select a few problem areas/topics first

Do a quick literature review on those topics

Lay out all the potential topics on the table

Discuss with your advisor(s) and Others

Keep your ability, interest, facilities and available time in mind

Don’t be hasty, explore in details and iterate if necessary

Do a detailed literature review on a couple of potential problem

topics that you select

Chart a scope of work – identify basic ingredients

Build slowly up and add spice to your work to increase its value

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Execute PhaseYou should• Think BIG / Out of the Box

• Sleep/shower/eat with the problem

• Explore all views of the problem

• Be well organized

• Prepare to delve into the abyss of the problem

• Document and surely backup data/results

You shouldn’t• Jump into quick conclusions

• Trust your own results until convinced by testing an

alternate method

• Discuss concepts with others whom you cannot trust

• Be afraid of hitting a brickwall because you may65

Conclusion Phase

• Write – Weekly reports documenting your work

– Conference/poster paper as soon as one part of work is partly done

– Journal paper as soon as one part of work is complete

– Dissertation chapter(s) as you make progress

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Attributes of a good researcher– Creative/Imaginative– Motivated– Inquisitive mind and Knowledgeable– Self-confident/Not Over-confident– Bold – Reasonable– Persuasive– Hardworking– Detailed– Patient– Organized– Maybe eccentric 67

THANKS

68

research overview and cognitive...

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