Research Overview and Cognitive Approaches

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Research overview and cognitive approaches

Partha P. Sarkar, Ph.D. Professor WESEP 594 January 24, 2013

• 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

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

Faculty Collaborators Dr. 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 6 and others …

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It is a team effort

WESEP Research 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. ASEE: Prism Nov. 2006 8

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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

Damage to Infrastructure US Losses (Rand Report)

Others 8% Flood 18% Every year on an average in the US: Wild Fire  $6.3 billion worth of wind damage including 12%  $1 billion worth of damage from tornadoes Earthquake Wind  $1.4 billion worth of damage from microburst 26% 36%  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

2000, Tornado Damage, Ft. Worth

1997, Rain-Wind Induced Fatigue Damage, Houston

2004, Hurricane Damage, 1992, Hurricane Damage, Tampa Miami 10 Wind Simulation and Testing Laboratory

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ISU Wind Engineering and Experimental Aerodynamics (WEEA) Program

Wind engineering efforts seek to understand and mitigate the damaging effects of wind on: •Built structures Aerodynamics/Aeroelasticity •Environment •People Structures Meteorology

Materials Statistics/Probability

Vibrations

Experimental aerodynamics efforts investigate basic aerodynamic problems in: •Aerospace •Agriculture •Environment •Transportation •Sports •Wind Energy 11 Wind Simulation and Testing Laboratory

Extreme Events are Transient in Nature

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

12 Wind Simulation and Testing Laboratory

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• My Background • My Research Overview and Approach • My Perspectives

Develop Facilities and Tools

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Wind Simulation and Testing (WiST) Lab Facilities Atmospheric Boundary Layer (ABL) Simulation 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.

Gust Generator

8 ft x 7.25 ft, 110 mph Aero: 8 ft x 6 ft, 110 mph 15

Bypass Duct for Gust Generation 1.40

1.30

) 1.20 initial V /

V 1.10

Velocity ( Velocity 1.00

0.90

0.80 -4 -2 0 2 4 6 8 10 12 Time (sec)

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Wind Simulation and Testing (WiST) Lab Facilities Tornado or Microburst Wind Simulation

• 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

Tornado/Microburst Simulator

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Tornado Mode

Fan Motor Turning Vane Open

0.3 m (1 ft) 1.83 m (6 ft)

Honeycomb/ 4 to 8 ft 1.52 m (5 ft) Screen

5.5 m (18 ft)

H = 1 to 5 ft

Adjustable Rotating downdraft ground plane

Aerospace Engineering

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

Vibration of structural systems  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

Contact: Prof. Partha Sarkar, AerE

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Modern Instruments: Fast, Accurate, Adequate

Instrumentation: Wind Tunnel

Vvert

Vtan Vrad Particle Image 18-hole Omniprobe for 3D Velocimetry Image velocity measurement

High-speed Digital Pressure Sonic Anemometer: Scanner DSA Series Field Measurement 21

Wind Simulation and Testing (WiST) Lab Facilities Instrumentation • 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 22

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ABL Simulation of Straight-Line Winds

Fig. 2 Dallas

Fig.1 Miami-Ft Lauderdale

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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)

r V r 2 Swirl Ratio  S(r)    max c 2Qinflow Qinflow

Tangential Velocity

Validation

Vane 5 (z=0.10r ) 1 c 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)

max Doppler on Wheels  0.5 /v  J. Wurman (2004,2005) v

01234 r/rc Tangential velocity profiles for tornado simulator and field radar data for Spencer, South Dakota tornado of 1998 and Mulhall, Oklahoma tornado of 1999. 28

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ISU Collaborative Effort Timothy M. Samaras

ISU Collaborative Effort

960

945

930

915

900

885

870

855

840 0 25 50 75 100 125 150 175 200 225 250

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Zhang and Sarkar, 2011 Instantaneous vortex structure at θv=15º, Low Swirl Ratio

Single-celled vortex

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

(a) Smooth ground Sub- (b) Rough ground II vortices

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Hu, Yang, Sarkar, Haan (2011)

Wind Engineering Research Tornado-Induced Wind Loads on Structures by Haan, Sarkar, Gallus, Balaramudu (NSF Sponsored)

Vane 5 (z=0.10r ) 1 c 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) max  0.5 /v  v Z X  Y

0 2 R1:LS:0o 01234 R1:HS:0o r/r c 1.5 R1:QS:0o Comparison of ISU Laboratory Simulated and Field Tornado Wind Speed Distributions 1 Fz C 0.5

0 Transient Roof Uplift Load Coefficient for a -0.5 34 Gable-Roofed Building in a Translating -6 -4 -2 0 2 4 6 Tornado, LS-Low Speed, HS- High-Speed X/D

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Results: Static Jet Microburst Simulation

rake 0.5 piv k-e 1.5 Wood sst k-w Rajarathnam 0 reaz Eqn. (1) rng NIMROD Doppler Radar rsm -0.5

Cp les Exp 1 -1

ROOF -1.5 1 2 1.5 x/H z/b

0.5 A

0.5 2.5 K FRONT x/H x/H

0 00.250.50.7511.25 0 3 2 1.5 Cp1 0.5 0 -1 -0.5Cp 0 0.5 1 U/Um Normalized Radial Velocity Profiles Pressure Coefficients for Building at 1D from Center of the Jet n U  z    z  Comparison of Different Turbulence  C   1 erf C  .... (1) U 1 b  2 b  m      models with Experimental Data

C 1 =1.52, C2 =0.68, n=1/6.5 35

Results: Moving Jet Microburst Simulation

2 S1 (CFD) 1.5 S1 (Exp) S1 (CFD) 1.5 S1 (Exp) 1 1 0.5 0.5 0 Cd

Cl 0 -0.5 -0.5 -1 -1 -1.5 -2 -1.5 -3 -2 -1 0 1 2 3 -3 -2 -1 0 1 2 3 X/D X/D Drag coefficient for 25.4 mm cube Lift coefficient for 25.4 mm cube

Jet Translation Speed1 = 0.225 m/s Nozzle Jet Exit Velocity = 10 m/s Nozzle Diameter = 203.2 mm (8 in.) 36

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Field Investigation of EF5 Tornado Disaster in Parkersburg, IA, May 25, 2008, Kikitsu and Sarkar (2010) 2nd St. 2nd 6 1st St.1st 57 N 14 6 0 0 0 An_l Florence St. 0 Ave. Newell 0 1 Elementary 1 0 As2_l Chur 0 School 0 2 1 0 1 Church 1 4 1 1 1 ch 1 2 2 2 2 3rd Ave. 4 2 2 2 2 2 1 3 2 3 4 2 7 7 High School 8 2 2 2 1 3 6 6 6 2 2 1 1 3 2 4 4 3rd Ave. As1_l 2 4 2 4 2 1 5 2 4 6 2 4 4 3 7 6 8 8 8 4 3 7 6 7 7 6 7 V 2 1 3 7 7 7 7 6 t 4 4 4 7 6 4 4 6 6 8 4 6 6 6 6 N Johnson St. Circle Dr. 7 8 8 8 8 0 7 Dr. Hilltop 4th Ave. 8 6 6 7 8 7 7 7 6 4 7 7 As1_r 7 7 7 4 4 8 8 3rd St.3rd 5th St.5th 4th St.4th 7 6 6 4 6 8 5 8 7 7 Lincoln St. 7 8 8 6 6 7 6 R 6 7 8 7 6 7 m 8 7 7 8 7 6 7 7 6 7 Bank A T D 57 14 57 i r 8 7 8 7 8 r a

e 6 7 n Industrial Warehouse c s Bank B

t 8 7 l i a 7 8 7 8 o Building t i n o Conn St. Model in ANSI/ n 4 7 8 7 6 4 7 6 7 As2_r 14 ANS 7 Fire Engine 6 7 8

7 S Johnson St. 6 4 Garage 6 6 Pleasant Dr. Dorothy Ave. 2 6 6 6 4 6 6 2 3 1 2 4 4 1 2 3 2 2 4 1 2 3 1 4 2 2 An_r 2 6 0 2 6 4 Enhanced Fujita Scale

2 2 0 Sunset Dr. 1 0 1 0 0 No Damage（0） 0 Butler County DOD= 1,2 DOD= 3,4 Parkersburg DOD= 5,6 DOD= 7,8 Des Moines DOD= 9,10 DOD= 9,10 37 Iowa State 0 100 200m （Residence where there were the dead）

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

Tanks Residence

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Thampi, Dayal and Sarkar, 2011

Case 1 Vs Case 2

Deflection in global Z Deflection in global X Von Mises stress • Case 1: X = -1.65r (125 mph), Case 2: X = 0.25r (180 mph) c c 40

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Thampi, Dayal, Sarkar, 2011

Final damage state of sealed building with Partially damaged example building at roof uplift connectors designed for 40 m/s Parkersburg (3-sec gust), with failed roof elements removed

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

Long-Term Monitoring Pluck test - Pole 1

Frequency (Hz) 0246810 200 100 0 -100 Pole 1 -200 Angle(deg) 500 3.33

400

300

200 Pull & release Amplitude

100 0.31 1.30 6.40 0 0246810 Frequency (Hz)

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%

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Mathematical modeling Equation of motion

x x x mx cx  kx  F  Fb  Fse y y y y U(z) my cy  ky  F  Fb  Fvs  Fse x Fb  FD ()cos  FL ()sin y Buffeting Fb  FD ()sin  FL ()cos 2  y y y  y 1 2 Y1(K)(1 2 ) Y2 (K)  F  U A D U D Z vs 2    CL (K)sin(t )  Y

X Vortex shedding

Mathematical modeling Buffeting functions

x y Fb  FD ()cos  FL ()sin Fb  FD ()sin  FL ()cos

1 2 dCD dCL 1 2 dCD dCL  (U  u) A[(CD  )  (CL  )]  (U  u) A[(C  )  (C  )] 2 d d 2 D d L d

1 2 2u v v 1 2 2u ' v v  U A(CD  CL ) (n),     U A[C  (C  C ) ] (n),    2 U U U 2 L U D L U U t t 1 2 u( ) v( ) 1 2 u( ) ' v( )  U A [2C ' (t  )  C ' (t  ) ]d  U A [2C ' (t  )  (C  C L )' (t  ) ]d 2  D u U L v U  L u D v 0 2 0 U U

Vortex shedding forcing function  y2 y y  1 Y (K)(1 )  Y (K) y 2  1 2 2  Fvs  U A D U D 2    CL (K)sin(t ) 

Y1 : Linear aeroelastic damping - from wind tunnel tests ε : Nonlinear aeroelastic damping - from wind tunnel tests

Y2 : Aeroelastic stiffness ~ negligible

CL : RMS lift coefficient  0 46

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Wind Tunnel Testing Dynamic Coil Springs 12 in. × 12 in. end plate with rounded corners

12-sided cylinder model Chain

0.75 in. Aluminum hollow rod

Leaf spring 22-lb capacity Force transducer

• Length: 20 in. • Mass: 0.19 slugs • Diameter: 4 in. (Corner to Corner) • Frequency: 7.15 Hz

• Range of Re: 3.5×103 ~ 5.5×104 47

0.5 0.4 0.3 Before 0.2 (in) Wind Tunnel Testing 0 0.1 “Lock-in” 0.0 -0.1 Dynamic: Strouhal number -0.2 -0.3 Amplitude, y -0.4 2.0 -0.5 012345 Time (sec) 0.5 1.5 0.4 “Lock-in” 0.3 0.2 (in)

0 0.1 n /f

s 1.0 0.0 f -0.1 St =0.2 -0.2 -0.3 0.5 “Lock-in” Amplitude, y -0.4 -0.5 012345 Time (sec) 0.0 0.5 0123456789100.4 After “Lock- 0.3 Reduced velocity, U/nD 0.2 in” (in)

0 0.1 0.0 -0.1 -0.2 -0.3 Amplitude, y -0.4 -0.5 48 012345 Time (sec)

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Wind Tunnel Testing Dynamic: Sc vs. Amplitude

0.20 Experiment for a 12-sided cylinder

Fitted equation for a 12-sided cylinder 0.15 /D 0 Griffin et al. for a circular cylinder

y 0 1.91 0.10  2 2 2.45 D [1  0.72  (8  π St Sc ]

y 1.29 0  2 2 3.35 Reduced amplitude, y amplitude, Reduced 0.05 D [1  0.43  (8  π S t  Sc )]

0.00 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Scruton number, Sc

Aerodynamic Force Modeling Comparison

10.0 8

1 ±3·σ S10 7.5 6 1 S12 X-Numerical Simuation 4 5.0

2 Stress-Range (ksi) 2.5 Stress-range (ksi) 0 0.0 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 45 50 1 min. mean wind speed (mph) 1 min. mean wind speed (mph) S12 8 ±3·σ 1 Peak 6 Y-Numerical Simuation 4 S10 2

Stress-range(ksi) U 0 0 5 10 15 20 25 30 35 40 1 min. mean wind speed (mph) 50

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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 Discussion Stationary Wind Case

3 Velocity, U (m/s) 2

0 0 5 10 15 20 Time (s)

Results and Discussion Stationary Wind Case

0.04 α 3 0.03 2 0.02 1 0.01 0 0 0 5 10 15 20

(deg) -1 (m) -0.01 0 5 10 15 20 -2 -0.02 -3 -0.03 -4 Torsional displacement, displacement, Torsional Vertical displacement, h Vertical -5 -0.04 Time (s) Time (s)

0.06 Numerical 0.2 Numerical Experimental Experimental 0.04 0.15

0.1 0.02 0.05 0 0 -0.02 -0.05 Lift coefficient, Cl Lift coefficient,

-0.1 Cm Moment coefficient, -0.04 -0.15 -0.06 -0.2 0 5 10 15 20 0 5 10 15 20 Time (s) Time (s) 54

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Mitigation of Wind Loads

Understanding Wind Loads

Cause Effect

Delta Wing Vortices on Roof

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Mitigation

Texas Tech WERFL

Conical Vortex Disrupter

Meteorological wind tunnel at CSU

Conical Vortex Mitigation 2 Disrupter Separated shear layer 0 -2 -4 Cp Building roof -6 -8 -10 Before Vo r t e x -12

2 Airflow induced 0

Wall Cp into bubble -2 After -4 57 0 100 200 300 400 500 600 700 800 900 Source: Sarkar, Wu, Banks and Meroney Time t (sec)

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

•

Upper Water Rivulet



WIND

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Full-scale tests for validation

Veteran’s Memorial Bridge, Port Arthur, TX

Full-scale tests for validation

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

Aerospace Engineering

Rain/wind-induced stay cable vibration

Circular Ring

2.5 With Upper 2 Rivulet Only

1.5 With Rivulet and 1 Rings @ 2D

0.5 Upper Water Rivulet With Rivulet and RMS of Displ. (in.) Displ. of RMS 0 Rings @ 4D 0 100 200 300 400 Reduced Velocity (=U/nD) 

WIND

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• My Background • My Research Overview and Approach • My Perspectives

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 Phase You 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 65 • Be afraid of hitting a brickwall because you may

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