Wind Tunnel Experiments Investigating the Aerodynamics of Sports Balls
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Transcript of Wind Tunnel Experiments Investigating the Aerodynamics of Sports Balls
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Wind Tunnel Experiments Wind Tunnel Experiments Investigating the Aerodynamics Investigating the Aerodynamics
of Sports Ballsof Sports Balls
Team Members:
Colin Jemmott
Sheldon Logan
Alexis Utvich
Advisor: Prof. Jenn Rossmann
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OverviewOverview
Motivation/BackgroundFlow VisualizationCalibration
– Pitot tube– Hot wire anemometer
Wiffle ball instrumentation/experimentsBaseball instrumentation/experiments
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MotivationMotivation
Previous studies have not produced a complete understanding of the flowfield around a spinning baseball
A comprehensive Wiffle ball study has not been documented before
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BackgroundBackground
Reynolds Number:
Re = ρVD/μLift Coefficient:
CL = 2FL/ρU2A
Drag Coefficient:
CD = 2FD/ρU2A
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Flow VisualizationFlow Visualization
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Calibration: Velocity ProfilesCalibration: Velocity Profiles
Measurements were taken to characterize flow in the test section
Pitot tube measurements were conducted at heights of 1, 2, 4, 6, 8, 10, and 11 in. and fan settings of 10, 30, and 50 Hz– Velocity profiles were constructed from these
measurements
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Calibration: Velocity ProfilesCalibration: Velocity Profiles10 Hz Velocity Profile
1690
1700
1710
1720
1730
1740
1750
1760
1770
1780
1790
1800
0 2 4 6 8 10 12
Height (in.)
Ve
loc
ity
(ft
/min
)
Front Middle Back
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Calibration: Hot-Wire Calibration: Hot-Wire AnemometerAnemometer
Device that determines airflow speed by measuring the rate of cooling of a heated wire.
Measures velocity fluctuations.
Turbulence level within tunnel was found to vary.
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Hot Wire Anemometer: 0.3% Hot Wire Anemometer: 0.3% TurbulenceTurbulence
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Hot Wire Anemometer: 0.5% Hot Wire Anemometer: 0.5% TurbulenceTurbulence
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Hot Wire Anemometer: 6% Hot Wire Anemometer: 6% TurbulenceTurbulence
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Hot Wire Anemometer: Variance Hot Wire Anemometer: Variance in Velocityin Velocity
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Stationary Ball Force Stationary Ball Force MeasurementsMeasurements
A nylon rod with strain gauges mounted on it was used to measure the lift and drag forces on stationary balls.
Two full bridges were placed on the nylon rod to measure both axial and bending effects.
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Schematic of Strain Gauge Schematic of Strain Gauge Device Device
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Schematic of DC AmplifierSchematic of DC Amplifier Gain ≈ 3000
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Amplifying CircuitAmplifying Circuit
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Orientation of Ball for Drag Orientation of Ball for Drag MeasurementsMeasurements
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Drag Coefficient: ResultsDrag Coefficient: Results The Drag Coefficient of the Wiffle ball was found
to decrease exponentially with respect to the Reynolds number.
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Lift ForceLift Force
It was discovered that Wiffle ball would experience a lift force if the holes of the ball were not symmetrically distributed about the horizontal axis.
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Lift Force: ResultsLift Force: Results The magnitude of the lift force seemed to depend
on the angle at which the ball was tilted.
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Lift Force: ResultsLift Force: Results One of the
potential reasons these lift forces come about is due to the air flowing into the ball.
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Lift Force: ResultsLift Force: Results
The lift force results in the deflection of the wake.
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Spinning Baseball ApparatusSpinning Baseball Apparatus
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Mass 0.32 lb 145 g
Diameter 2.86 in 7.26 cm
Velocity 80 MPH 36 m/s
Angular Velocity 1800 rpm 30 Hz
Lift Force 0.18 lb 0.79 N
Lift Coefficient 0.20 -
Drag Force 0.37 lb 1.7 N
Drag Coefficient 0.54 -
Mathematical Breakdown of a Mathematical Breakdown of a CurveballCurveball
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Forces on an 1800 rpm Baseball
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0.4
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0.8
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0 20 40 60 80 100 120
Velocity (mph)
Fo
rce
in U
nit
s o
f th
e B
all's
Wei
gh
t Drag
Lift
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Lift on a Spinning Baseball
0
0.05
0.1
0.15
0.2
0.25
0 0.2 0.4 0.6 0.8 1Spin Number (Rw/V)
Co
effi
cen
t o
f L
ift
0.4 E 5
0.8 E 5
1.2 E 5
1.7 E 5
2.1 E 5
Briggs 2.0 E 5
Briggs 1.7 E 5
Briggs 1.4 E 5
Briggs 1.0 E 5
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Coefficient Coefficient of Lift by of Lift by
Spin Spin Parameter Parameter
ComparisonComparison
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ConclusionConclusion
Turbulence levels in the wind tunnel are satisfactorily low.
Lift force on a Wiffle ball is dependent on its orientation.
Lift coefficient for a spinning baseball was found to have stronger dependence on Reynolds number than previously reported.
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AcknowledgementsAcknowledgements
Sam AbdelmuatiMike WheelerProf. Carl BaumgaertnerProfs Bright, Cha, and DuronProf. Joe KingProf. Toby RossmannProf. Jenn Rossmann