1. Wind Tunnel Experiments Investigating the Aerodynamics of Sports Balls Team Members: Colin Jemmott Sheldon Logan Alexis Utvich Advisor: Prof. Jenn Rossmann

2. Overview Motivation/Background Flow Visualization Calibration – Pitot tube – Hot wire anemometer Wiffle ball instrumentation/experiments Baseball instrumentation/experiments

3. 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

4. Background Reynolds Number: Re = ρVD/μ Lift Coefficient: C L = 2F L /ρU 2 A Drag Coefficient: C D = 2F D /ρU 2 A

5. Flow Visualization

6. 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

7. Calibration: Velocity Profiles

8. 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.

9. Hot Wire Anemometer: 0.3% Turbulence

10. Hot Wire Anemometer: 0.5% Turbulence

11. Hot Wire Anemometer: 6% Turbulence

12. Hot Wire Anemometer: Variance in Velocity

13. 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.

14. Schematic of Strain Gauge Device

15. Schematic of DC Amplifier Gain ≈ 3000

16. Amplifying Circuit

17. Orientation of Ball for Drag Measurements

18. Drag Coefficient: Results The Drag Coefficient of the Wiffle ball was found to decrease exponentially with respect to the Reynolds number.

19. 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.

20. Lift Force: Results The magnitude of the lift force seemed to depend on the angle at which the ball was tilted.

21. Lift Force: Results One of the potential reasons these lift forces come about is due to the air flowing into the ball.

22. Lift Force: Results The lift force results in the deflection of the wake.

24. Spinning Baseball Apparatus

25. Mass0.32 lb145 g Diameter2.86 in7.26 cm Velocity80 MPH36 m/s Angular Velocity1800 rpm30 Hz Lift Force0.18 lb0.79 N Lift Coefficient0.20- Drag Force0.37 lb1.7 N Drag Coefficient0.54- Mathematical Breakdown of a Curveball

28. Coefficient of Lift by Spin Parameter Comparison

29. 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.

30. Acknowledgements Sam Abdelmuati Mike Wheeler Prof. Carl Baumgaertner Profs Bright, Cha, and Duron Prof. Joe King Prof. Toby Rossmann Prof. Jenn Rossmann