My Masters thesis defense presentation.

1. THE AERODYNAMICS OF THE KNUCKLEBALL PITCH: AN EXPERIMENTAL INVESTIGATION INTO THE EFFECTS THAT THE SEAM AND SLOW ROTATION HAVE ON A BASEBALL By: Michael Morrissey Advisor: Dr. John Borg Committee Members: Dr. Jon Koch and Dr. Phillip Voglewede

2. Different Pitches *All of these conditions are dependent upon the individual pitcher. [1] Adair, R.K., The Physics of Baseball. 1994, New York: HarperCollins. 2

3. Baseball Terminology Four-Seam Orientation Two-Seam Orientation 3

4. Baseball Terminology 2 elongated figure “8” pieces of cowhide Cowhide is held together with red stitches Horseshoe lies behind seam Landing strip is along long piece of cowhide 4

5. Background of the Knuckleball Invented by Eddie “Knuckles” Cicotte around 1908 Perplexing because path of knuckleball never seems to repeat under same conditions “I always thought the knuckleball was the easiest pitch to catch. Wait'll it stops rolling, then go to the backstop and pick it up.”- Bob Uecker [2] Clark, D., The Knucklebook. 2006, Chicago: Ivan R. Dee. 5

6. Background of the Knuckleball Prolific Knuckleball pitchers: Hoyt Wilhelm (5 time All-Star, Hall of Fame) Phil Niekro (5 time All-Star, Hall of Fame) Jesse Haines (Hall of Fame) Current MLB Knuckleballers: Tim Wakefield, Boston Red Sox R.A. Dickey, Minnesota Twins Josh Banks, San Diego Padres Charlie Haegar, Los Angeles Dodgers 6

7. Interview with R.A. Dickey 7 Jim Caple (ESPN) interview of R.A. Dickey on Mar 17, 2008

8. Strong Points in Interview with R.A. Dickey Feel is important Places fingernails into horseshoe area for grip Create late movement “Ball grips into air” Easiest pitch to throw, hardest to master Same pitch, different paths Good places for knuckleball: High wind and humidity Boston and Pittsburgh Bad places for knuckleball: High heat Arizona and Colorado Springs 8

9. Characteristics of the Knuckleball 65 – 80 mph (95 – 117 ft/s) Reynolds number of 1.4x105 to 1.8x105 Data will be collected at 70 mph Two-seam orientation Rotation rate of 50 rpm One half of a rotation from pitcher to catcher 9 Tim Wakefield Phil Niekro Eddie Cocotte

10. Movement of the Knuckleball 10 ViewDo: How To Throw a Knuckleball. June 16, 2006

11. Literature Review 1672- Newton noticed how flight of tennis ball was affected by spin[3] 1852- Magnus found that rotation of cylinder created a lateral force[4] 1904- Prandtl discovered the boundary layer concept[5] [3] Newton, I., New Theory of Light and Colours. Philos. Trans. R. Soc., 1672: p. 678-688. [4] Magnus, G., On the Deviation of Projectiles; and on a Remarkable Phenomenon of Rotating Bodies. Memoirs of the Royal Academy, 1852: p. 210-231. [5] Prandtl, L., Essentials of Fluid Dynamics. 1952, New York: Hafner Publishing Company, Inc. 11

12. Literature Review 1959- Lyman Briggs was first find deflection of baseball due to spin 1971- Brown recorded flow visualization photos of baseball Brown’s photo of a spinning baseball with a rate of 900 rpm, counter-clockwise, and a speed of 70 ft/sec (47 mph). Seams and rotation provide a downward trajectory. (Brown, 1971) Brown’s photo of a stationary baseball. Seams, alone, produce lift. (Brown, 1971) [6] Brown, F.N.M., See the Wind Blow. 1971, Department of Aerospace and Mechanical Engineering, University of Notre Dame. 12

13. Literature Review 1975- Watts and Sawyer recorded lateral force of baseball in 4-seam orientation at 46 mph as a function of different azimuthal angle Watts and Sawyer’s orientation of the baseball in the wind tunnel. (Watts and Sawyer, 1975) Watts and Sawyer’s results of the lateral force imbalance of a four-seam baseball as the angle changes. (Watts and Sawyer, 1975) [7] Watts, R.G. and E. Sawyer, Aerodynamics of a Knuckleball. American Journal of Physics, 1975. 43: p. 960-963. 13

14. Motivation and Methodology To find why the knuckleball moves erratically What effect do the seams and rotation have on the aerodynamics of the knuckleball Methods: Force Balance Dynamometry Flow Visualization Hot Film Anemometry 14

15. Force Balance: Goals Match Watts and Sawyer’s lift data 4-seam orientation, 46 mph, statically 4-seam orientation, 46 mph, spinning Find lift from knuckleball conditions 2-seam orientation, 70 mph, spinning 15

16. Force Balance: Match Watts and Sawyer’s Data 4-Seam baseball, rotating statically, at 46 mph Follow minima and maxima as well as trend 4-seam baseball is symmetric twice 16

17. Force Balance: 4-Seam at 46 mph Data Lift oscillates between -0.1 to 0.1 lbs Lift goes in the direction of the nearest seam There is a variance when the stagnation is at a seam or midpoint between seams 17

18. Force Balance: Wind Tunnel Setup Force Balance with spinning strut 12 V DC motor was used to rotate baseball Laser diode system was built to measure rotation rate 1 slit chopper plate 36 slit chopper plate 18 DC Motor Photo Diode Laser

19. Force Balance: Spinning Strut, Static and Spinning Data Spinning strut data matches previous data 19

20. Force Balance: Frequency Filter 20 Blade Pass Frequency: 280 Hz

21. Force Balance: 2-Seam Knuckleball Peak of lift is at 170° Minimum of lift is at 190° Orientation of baseball during data collection shown at right 21

22. Force Balance: 2-Seam Knuckleball Maximum of lift is at 170°, which is near seam What effect does the seam have on the lift? Lift goes in the direction of the nearest seam when within 30° from stagnation Lateral force changes positive and negative, but not as much as the lift 22

23. Force Balance: Standard Deviations Standard deviation of each lift was found 2-Seam, spinning baseball had greatest variation This concludes that the lift is not consistent per angle of rotation Leads to unpredictability of baseball 23

24. Flow Visualization: Goals Match existing data Separation on smooth sphere Study how separation changes as baseball rotates Find separation on landing strip and across the seams 24

25. Flow Visualization: Setup Sage Action Helium Bubble Generator Photron Fastcam-APX RS CMOS high speed camera Laser diode system HP Oscilloscope Lighting system Two halogen lamps Two fresnel lenses Two black covers Matlab programs 25

26. Flow Visualization: Matlab Code Problem with helium bubbles is that only a few are visible at a given time Matlab code superimposed images together 300 helium bubble photographs Protractor Fiducial tracer Matlab code rotated image so stagnation was at 0° 26

27. Flow Visualization: Separation on Smooth Sphere Superimposed image of helium bubbles on smooth sphere Separation is at 107±5° Accepted value is 110°[9] Flow visualization method is correct to use for data collection 27 [8] Chang, P.K., Separation of Flow. 1970, Oxford, New York: Pergamon Press.

28. Flow Visualization: Separation on Baseball Seam induces separation Separation on landing strip is at 104±5° Near sphere of 107±5° 28

29. Flow Visualization: Separation as Baseball Rotates 29

30. Flow Visualization: Details of Separation on Rotating Baseball Separation varies from 88° to 122° during one rotation Seam carries separation so separation is induced by the seam Most movement of separation is during first 180° 30

31. Flow Visualization: Separation and Lift Slight correlation between lift and separation Largest change in separation is between 90° to 130° 31

32. Hot Film Anemometry: Goals Build hot film plug Calibrate with a smooth sphere Match published data Make observations with smooth sphere and trip wire Collect data: Landing Strip Before and after seam, clockwise Before and after seam, counter-clockwise 32

33. Hot Film Anemometry: Assembly ¼” diameter plug, 1” long Acrylic Aluminum tube 5 micron diameter tungsten wire 33 5 µm tungsten wire

34. Hot Film Anemometry: Calibration Achenbach shear profile was used to calibrate the hot films Achenbach found shear stress on a smooth sphere as a function of degrees King’s Law was used for shear stress, where n=1/3 34 [9] Achenbach, E., Experiments on the Flow Past Spheres at Very High Reynolds Numbers. Journal of Fluid Mechanics, 1972. 54: p. 565-575.

35. Hot Film Anemometry: Match Achenbach’s Data Hot film was placed in smooth sphere at same Re of Achenbach, Re=1.6x105 Smooth sphere data fits published data Hot film was placed orthogonal and parallel to the flow Shear stress is much lower when hot film is parallel 35 [10] Achenbach, E., Experiments on the Flow Past Spheres at Very High Reynolds Numbers. Journal of Fluid Mechanics, 1972. 54: p. 565-575.

36. Hot Film Anemometry: Shear Stress on a Smooth Sphere with Trip Wire Shear stress was found on smooth sphere with trip wire Hot film parallel to flow was small, once again Hot film upstream of trip wire experienced decrease in shear at 60° Hot film downstream of trip wire experienced largest increase in shear at 45° 36

37. Hot Film Anemometry: Effect of Trip Wire on Smooth Sphere Tripping wire was placed 60° upstream from the hot film Shear stress matches smooth sphere data up to 60° Tripping wire delays separation when trip wire is 10° to 60° from stagnation 37

38. Hot Film Anemometry: Positions in Baseball Hot films were placed in the landing strip and between the seams Perpendicular to free stream velocity Hot films surrounding seam were used while ball was rotating clockwise and counter-clockwise Together, this allowed 5 hot films on one ball 38

39. Hot Film Anemometry: Morrissey and Achenbach Data Shear stress on landing strip of baseball almost identical to the shear stress found by Achenbach 39

40. Hot Film Anemometry: Shear Stress at Landing Strip Stagnation is at 180° Shear stress is zero because flow follows curvature of ball Maximum shear is about 60° from stagnation Turbulent wake 288° to 81° Relatively symmetrical over stagnation Flow visualization images match hot film data 40

41. Hot Film Anemometry: Shear Stress on Landing Strip Shear stress is greater as the ball rotates away from stagnation Local Reynolds number is greater as the hot film rotates towards stagnation Could rotation delay separation on bottom half of baseball? 41

42. Hot Film Anemometry: Separation Difference in Respect to Rotation Separation is delayed when hot film is rotating away Hot film between seams record small amounts of shear stress Hot film upstream of seams have less shear than hot film downstream of seam Hot film downstream of seam has small change of slope at 40° 42

43. Hot Film Anemometry: Smooth Sphere Trip Wire Compared to Baseball Data Baseball data is when hot film is rotating towards stagnation Nearly same trends are noticed of shear stress when hot film is placed upstream and downstream of trip wire and baseball seam Therefore, seam acts as a trip wire Seam delays separation? 43

44. Hot Film Anemometry: Delayed Separation and Lift Most knuckleball pitchers hold the baseball at 120° azimuthal angle Most change in lift is during the knuckleball rotation This large change achieves the deception a baseball pitcher is looking for 44

45. Hot Film Anemometry: Delayed Separation and Lift At 170°, lift is at it’s maximum A seam is 20° and 40° away from each side of stagnation Trip wire shows that separation delay is when trip wire is 10° to 60° from stagnation Therefore, delayed separation occurs on right side of ball. Conclusively, lift is to the left Same occurs at 190° when lift is at it’s minimum 45

46. Overall Summary Landing Strip acts as a smooth sphere Flow visualization and hot film Seams carry separation toward and away from stagnation Flow visualization and hot film Seams initiate and delay separation Initiate at when seam is 90° to 120° from stagnation (flow visualization and hot film) Evidence that separation is delayed when seam is 10° to 60° from stagnation (hot film) Evidence that rotation of baseball delays separation (not confirmed) Magnus effect is only 6.579x10-7 lbs 46

47. Future Work Lift and lateral forces as function of pressure and humidity Chase Field, Phoenix, Arizona- Lowest humidity Minute Maid Ballpark, Houston, Texas- Highest humidity Fenway Park, Boston, Massachusetts- Highest pressure Coors Field, Denver, Colorado- Lowest pressure Flow visualization Bottom half of the baseball Side of the baseball Ink dot and solvent Confirm that seam delays separation 47

48. Acknowledgements Advisor: Dr. John Borg Committee Members: Dr. Jon Koch Dr. Phillip Voglewede Machinists: Ray Hamilton Tom Silman Dave Gibas Dr. Robert Nelson at Notre Dame University 48

49. Questions? 49

50. BACKUP SLIDES 50

51. Baseball Setup Holes for baseball were found for each orientation 4-seam: Midpoint between seams 2-seam: Repeat 4-seam process on each side Midpoint between points was found Checked with distance between seams 51

52. Baseball Orientation Before any setup was constructed, it was important to configure the direction of the force vectors This was then applied to ELD’s force balance dynamometer 52

53. Force Balance: Wind Tunnel Setup Design of a peep hole, mirror, and protractor was used to view orientation of baseball 53

54. Force Balance: Calibration Calibration was done with a series of weights Drawing of lift calibration 54

55. Force Balance: Apparatus Force balance recorded lift and drag Force balance was rotated to record lift and lateral forces Two different stings were used: Static strut Spinning strut 55

56. Hot Film Anemometry: Data is mirrored at 180° 56

57. Hot Film Anemometry: 57

58. Literature Review 2001- Leroy Alaways and Mont Hubbard, along with Sikorsky and Watts and Ferrer’s data found that orientation of baseball and spin parameter changes the lift coefficient The combination of all three data sets, showing the relationship between all three. (Alaways and Hubbard, 2001) [8] Alaways, L.W. and M. Hubbard, Experimental Determination of Baseball Spin and Lift. Journal of Sports Sciences, 2001. 19: p. 349-358. 58

59. Force Balance: Magnus Effect Coefficient of Lift, Spin Parameter, is 0.001014 59 Magnus force is calculated to be 6.579x10-7 lbs, therefore, negligible

60. Conclusion: Hot Film Anemometry High shear stress when ball is initially rotating Shear stress causes the baseball to rotate backward 60

61. Conclusion: Flow Visualization Seams control rotation rate until the pressure recovers over the seam 61