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Wind Tunnel Experiments Investigating the Aerodynamics of Sports Balls. Team Members: Colin Jemmott Sheldon Logan Alexis Utvich Advisor: Prof. Jenn Rossmann. Overview. Motivation/Background Flow Visualization Calibration Pitot tube Hot wire anemometer
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Wind Tunnel Experiments Investigating the Aerodynamics of Sports Balls Team Members: Colin Jemmott Sheldon Logan Alexis Utvich Advisor: Prof. Jenn Rossmann
Overview • Motivation/Background • Flow Visualization • Calibration • Pitot tube • Hot wire anemometer • Wiffle ball instrumentation/experiments • Baseball instrumentation/experiments
Motivation • 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
Background • Reynolds Number: Re = ρVD/μ • Lift Coefficient: CL = 2FL/ρU2A • Drag Coefficient: CD = 2FD/ρU2A
Calibration: 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: Hot-Wire Anemometer • 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.
Stationary Ball Force Measurements • 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 DC Amplifier • Gain ≈ 3000
Drag Coefficient: Results • The Drag Coefficient of the Wiffle ball was found to decrease exponentially with respect to the Reynolds number.
Lift 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: Results • The magnitude of the lift force seemed to depend on the angle at which the ball was tilted.
Lift Force: Results • One of the potential reasons these lift forces come about is due to the air flowing into the ball.
Lift Force: Results • The lift force results in the deflection of the wake.
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 Curveball
Conclusion • 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.
Acknowledgements • Sam Abdelmuati • Mike Wheeler • Prof. Carl Baumgaertner • Profs Bright, Cha, and Duron • Prof. Joe King • Prof. Toby Rossmann • Prof. Jenn Rossmann