wind tunnel experiments investigating the aerodynamics of sports balls team members: colin jemmott...

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

OverviewOverview

Motivation/BackgroundFlow VisualizationCalibration

– Pitot tube– Hot wire anemometer

Wiffle ball instrumentation/experimentsBaseball instrumentation/experiments

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

BackgroundBackground

Reynolds Number:

Re = ρVD/μLift Coefficient:

CL = 2FL/ρU2A

Drag Coefficient:

CD = 2FD/ρU2A

Flow VisualizationFlow Visualization

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

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

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.

Hot Wire Anemometer: 0.3% Hot Wire Anemometer: 0.3% TurbulenceTurbulence

Hot Wire Anemometer: 0.5% Hot Wire Anemometer: 0.5% TurbulenceTurbulence

Hot Wire Anemometer: 6% Hot Wire Anemometer: 6% TurbulenceTurbulence

Hot Wire Anemometer: Variance Hot Wire Anemometer: Variance in Velocityin Velocity

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.

Schematic of Strain Gauge Schematic of Strain Gauge Device Device

Schematic of DC AmplifierSchematic of DC Amplifier Gain ≈ 3000

Amplifying CircuitAmplifying Circuit

Orientation of Ball for Drag Orientation of Ball for Drag MeasurementsMeasurements

Drag Coefficient: ResultsDrag Coefficient: Results The Drag Coefficient of the Wiffle ball was found

to decrease exponentially with respect to the Reynolds number.

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.

Lift Force: ResultsLift Force: Results The magnitude of the lift force seemed to depend

on the angle at which the ball was tilted.

Lift Force: ResultsLift Force: Results One of the

potential reasons these lift forces come about is due to the air flowing into the ball.

Lift Force: ResultsLift Force: Results

The lift force results in the deflection of the wake.

Spinning Baseball ApparatusSpinning Baseball Apparatus

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

Forces on an 1800 rpm Baseball

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

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

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

Coefficient Coefficient of Lift by of Lift by

Spin Spin Parameter Parameter

ComparisonComparison

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.

AcknowledgementsAcknowledgements

Sam AbdelmuatiMike WheelerProf. Carl BaumgaertnerProfs Bright, Cha, and DuronProf. Joe KingProf. Toby RossmannProf. Jenn Rossmann