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- 1. THE AERODYNAMICS OF THE KNUCKLEBALL PITCH: AN EXPERIMENTAL INVESTIGATION INTO THE EFFECTS THAT THE SEAM AND SLOW ROTATION HAVE ON A BASEBALL<br />By: Michael Morrissey<br />Advisor: Dr. John Borg<br />Committee Members: Dr. Jon Koch and Dr. Phillip Voglewede<br />
- 2. Different Pitches<br />*All of these conditions are dependent upon the individual pitcher.<br />[1] Adair, R.K., The Physics of Baseball. 1994, New York: HarperCollins.<br />2<br />
- 3. Baseball Terminology<br />Four-Seam Orientation<br />Two-Seam Orientation<br />3<br />
- 4. Baseball Terminology<br />2 elongated figure “8” pieces of cowhide<br />Cowhide is held together with red stitches<br />Horseshoe lies behind seam<br />Landing strip is along long piece of cowhide<br />4<br />
- 5. Background of the Knuckleball<br />Invented by Eddie “Knuckles” Cicotte around 1908<br />Perplexing because path of knuckleball never seems to repeat under same conditions<br />“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<br />[2] Clark, D., The Knucklebook. 2006, Chicago: Ivan R. Dee.<br />5<br />
- 6. Background of the Knuckleball<br />Prolific Knuckleball pitchers:<br />Hoyt Wilhelm (5 time All-Star, Hall of Fame)<br />Phil Niekro (5 time All-Star, Hall of Fame)<br />Jesse Haines (Hall of Fame)<br />Current MLB Knuckleballers:<br />Tim Wakefield, Boston Red Sox<br />R.A. Dickey, Minnesota Twins<br />Josh Banks, San Diego Padres<br />Charlie Haegar, Los Angeles Dodgers<br />6<br />
- 7. Interview with R.A. Dickey<br />7<br />Jim Caple (ESPN) interview of R.A. Dickey on Mar 17, 2008<br />
- 8. Strong Points in Interview with R.A. Dickey<br />Feel is important<br />Places fingernails into horseshoe area for grip<br />Create late movement<br />“Ball grips into air”<br />Easiest pitch to throw, hardest to master<br />Same pitch, different paths<br />Good places for knuckleball:<br />High wind and humidity<br />Boston and Pittsburgh<br />Bad places for knuckleball:<br />High heat<br />Arizona and Colorado Springs<br />8<br />
- 9. Characteristics of the Knuckleball<br />65 – 80 mph (95 – 117 ft/s)<br />Reynolds number of 1.4x105 to 1.8x105<br />Data will be collected at 70 mph<br />Two-seam orientation<br />Rotation rate of 50 rpm<br />One half of a rotation from pitcher to catcher<br />9<br />Tim Wakefield<br />Phil Niekro<br />Eddie Cocotte<br />
- 10. Movement of the Knuckleball<br />10<br />ViewDo: How To Throw a Knuckleball. June 16, 2006<br />
- 11. Literature Review<br />1672- Newton noticed how flight of tennis ball was affected by spin[3]<br />1852- Magnus found that rotation of cylinder created a lateral force[4]<br />1904- Prandtl discovered the boundary layer concept[5]<br />[3] Newton, I., New Theory of Light and Colours. Philos. Trans. R. Soc., 1672: p. 678-688.<br />[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.<br />[5] Prandtl, L., Essentials of Fluid Dynamics. 1952, New York: Hafner Publishing Company, Inc.<br />11<br />
- 12. Literature Review<br />1959- Lyman Briggs was first find deflection of baseball due to spin<br />1971- Brown recorded flow visualization photos of baseball<br />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)<br />Brown’s photo of a stationary baseball. Seams, alone, produce lift. (Brown, 1971)<br />[6] Brown, F.N.M., See the Wind Blow. 1971, Department of Aerospace and Mechanical Engineering, University of Notre Dame.<br />12<br />
- 13. Literature Review<br />1975- Watts and Sawyer recorded lateral force of baseball in 4-seam orientation at 46 mph as a function of different azimuthal angle<br />Watts and Sawyer’s orientation of the baseball in the wind tunnel. (Watts and Sawyer, 1975)<br />Watts and Sawyer’s results of the lateral force imbalance of a four-seam baseball as the angle changes. (Watts and Sawyer, 1975)<br />[7] Watts, R.G. and E. Sawyer, Aerodynamics of a Knuckleball. American Journal of Physics, 1975. 43: p. 960-963.<br />13<br />
- 14. Motivation and Methodology<br />To find why the knuckleball moves erratically<br />What effect do the seams and rotation have on the aerodynamics of the knuckleball<br />Methods:<br />Force Balance Dynamometry<br />Flow Visualization<br />Hot Film Anemometry<br />14<br />
- 15. Force Balance: Goals<br />Match Watts and Sawyer’s lift data<br />4-seam orientation, 46 mph, statically<br />4-seam orientation, 46 mph, spinning<br />Find lift from knuckleball conditions<br />2-seam orientation, 70 mph, spinning<br />15<br />
- 16. Force Balance: Match Watts and Sawyer’s Data<br />4-Seam baseball, rotating statically, at 46 mph<br />Follow minima and maxima as well as trend<br />4-seam baseball is symmetric twice<br />16<br />
- 17. Force Balance: 4-Seam at 46 mph Data<br />Lift oscillates between -0.1 to 0.1 lbs<br />Lift goes in the direction of the nearest seam<br />There is a variance when the stagnation is at a seam or midpoint between seams<br />17<br />
- 18. Force Balance: Wind Tunnel Setup<br />Force Balance with spinning strut<br />12 V DC motor was used to rotate baseball<br />Laser diode system was built to measure rotation rate<br />1 slit chopper plate<br />36 slit chopper plate<br />18<br />DC Motor<br />Photo Diode<br />Laser<br />
- 19. Force Balance: Spinning Strut, Static and Spinning Data<br />Spinning strut data matches previous data<br />19<br />
- 20. Force Balance: Frequency Filter<br />20<br />Blade Pass Frequency: 280 Hz<br />
- 21. Force Balance: 2-Seam Knuckleball<br />Peak of lift is at 170°<br />Minimum of lift is at 190°<br />Orientation of baseball during data collection shown at right<br />21<br />
- 22. Force Balance: 2-Seam Knuckleball<br />Maximum of lift is at 170°, which is near seam<br />What effect does the seam have on the lift?<br />Lift goes in the direction of the nearest seam when within 30° from stagnation<br />Lateral force changes positive and negative, but not as much as the lift<br />22<br />
- 23. Force Balance: Standard Deviations<br />Standard deviation of each lift was found<br />2-Seam, spinning baseball had greatest variation<br />This concludes that the lift is not consistent per angle of rotation<br />Leads to unpredictability of baseball<br />23<br />
- 24. Flow Visualization: Goals<br />Match existing data<br />Separation on smooth sphere<br />Study how separation changes as baseball rotates<br />Find separation on landing strip and across the seams<br />24<br />
- 25. Flow Visualization: Setup<br />Sage Action Helium Bubble Generator<br />Photron Fastcam-APX RS CMOS high speed camera<br />Laser diode system<br />HP Oscilloscope<br />Lighting system<br />Two halogen lamps<br />Two fresnel lenses<br />Two black covers<br />Matlab programs<br />25<br />
- 26. Flow Visualization: Matlab Code<br />Problem with helium bubbles is that only a few are visible at a given time<br />Matlab code superimposed images together<br />300 helium bubble photographs<br />Protractor<br />Fiducial tracer<br />Matlab code rotated image so stagnation was at 0°<br />26<br />
- 27. Flow Visualization: Separation on Smooth Sphere<br />Superimposed image of helium bubbles on smooth sphere<br />Separation is at 107±5°<br />Accepted value is 110°[9]<br />Flow visualization method is correct to use for data collection<br />27<br />[8] Chang, P.K., Separation of Flow. 1970, Oxford, New York: Pergamon Press.<br />
- 28. Flow Visualization: Separation on Baseball<br />Seam induces separation<br />Separation on landing strip is at 104±5°<br />Near sphere of 107±5°<br />28<br />
- 29. Flow Visualization: Separation as Baseball Rotates<br />29<br />
- 30. Flow Visualization: Details of Separation on Rotating Baseball<br />Separation varies from 88° to 122° during one rotation<br />Seam carries separation so separation is induced by the seam<br />Most movement of separation is during first 180°<br />30<br />
- 31. Flow Visualization: Separation and Lift<br />Slight correlation between lift and separation<br />Largest change in separation is between 90° to 130°<br />31<br />
- 32. Hot Film Anemometry: Goals<br />Build hot film plug<br />Calibrate with a smooth sphere<br />Match published data<br />Make observations with smooth sphere and trip wire<br />Collect data:<br />Landing Strip<br />Before and after seam, clockwise<br />Before and after seam, counter-clockwise<br />32<br />
- 33. Hot Film Anemometry: Assembly<br />¼” diameter plug, 1” long<br />Acrylic<br />Aluminum tube<br />5 micron diameter tungsten wire<br />33<br />5 µm tungsten wire<br />
- 34. Hot Film Anemometry: Calibration<br />Achenbach shear profile was used to calibrate the hot films<br />Achenbach found shear stress on a smooth sphere as a function of degrees<br />King’s Law was used for shear stress, where n=1/3<br />34<br />[9] Achenbach, E., Experiments on the Flow Past Spheres at Very High Reynolds Numbers. Journal of Fluid Mechanics, 1972. 54: p. 565-575.<br />
- 35. Hot Film Anemometry: Match Achenbach’s Data<br />Hot film was placed in smooth sphere at same Re of Achenbach, Re=1.6x105<br />Smooth sphere data fits published data<br />Hot film was placed orthogonal and parallel to the flow<br />Shear stress is much lower when hot film is parallel<br />35<br />[10] Achenbach, E., Experiments on the Flow Past Spheres at Very High Reynolds Numbers. Journal of Fluid Mechanics, 1972. 54: p. 565-575.<br />
- 36. Hot Film Anemometry: Shear Stress on a Smooth Sphere with Trip Wire<br />Shear stress was found on smooth sphere with trip wire<br />Hot film parallel to flow was small, once again<br />Hot film upstream of trip wire experienced decrease in shear at 60°<br />Hot film downstream of trip wire experienced largest increase in shear at 45°<br />36<br />
- 37. Hot Film Anemometry: Effect of Trip Wire on Smooth Sphere<br />Tripping wire was placed 60° upstream from the hot film<br />Shear stress matches smooth sphere data up to 60°<br />Tripping wire delays separation when trip wire is 10° to 60° from stagnation<br />37<br />
- 38. Hot Film Anemometry: Positions in Baseball<br />Hot films were placed in the landing strip and between the seams<br />Perpendicular to free stream velocity<br />Hot films surrounding seam were used while ball was rotating clockwise and counter-clockwise<br />Together, this allowed 5 hot films on one ball<br />38<br />
- 39. Hot Film Anemometry: Morrissey and Achenbach Data<br />Shear stress on landing strip of baseball almost identical to the shear stress found by Achenbach<br />39<br />
- 40. Hot Film Anemometry: Shear Stress at Landing Strip<br />Stagnation is at 180°<br />Shear stress is zero because flow follows curvature of ball<br />Maximum shear is about 60° from stagnation<br />Turbulent wake 288° to 81°<br />Relatively symmetrical over stagnation<br />Flow visualization images match hot film data<br />40<br />
- 41. Hot Film Anemometry: Shear Stress on Landing Strip<br />Shear stress is greater as the ball rotates away from stagnation<br />Local Reynolds number is greater as the hot film rotates towards stagnation<br />Could rotation delay separation on bottom half of baseball?<br />41<br />
- 42. Hot Film Anemometry: Separation Difference in Respect to Rotation <br />Separation is delayed when hot film is rotating away<br />Hot film between seams record small amounts of shear stress<br />Hot film upstream of seams have less shear than hot film downstream of seam<br />Hot film downstream of seam has small change of slope at 40°<br />42<br />
- 43. Hot Film Anemometry: Smooth Sphere Trip Wire Compared to Baseball Data<br />Baseball data is when hot film is rotating towards stagnation<br />Nearly same trends are noticed of shear stress when hot film is placed upstream and downstream of trip wire and baseball seam<br />Therefore, seam acts as a trip wire<br />Seam delays separation?<br />43<br />
- 44. Hot Film Anemometry: Delayed Separation and Lift<br />Most knuckleball pitchers hold the baseball at 120° azimuthal angle<br />Most change in lift is during the knuckleball rotation<br />This large change achieves the deception a baseball pitcher is looking for<br />44<br />
- 45. Hot Film Anemometry: Delayed Separation and Lift<br />At 170°, lift is at it’s maximum<br />A seam is 20° and 40° away from each side of stagnation<br />Trip wire shows that separation delay is when trip wire is 10° to 60° from stagnation<br />Therefore, delayed separation occurs on right side of ball. Conclusively, lift is to the left <br />Same occurs at 190° when lift is at it’s minimum<br />45<br />
- 46. Overall Summary<br />Landing Strip acts as a smooth sphere<br />Flow visualization and hot film<br />Seams carry separation toward and away from stagnation<br />Flow visualization and hot film<br />Seams initiate and delay separation<br />Initiate at when seam is 90° to 120° from stagnation (flow visualization and hot film)<br />Evidence that separation is delayed when seam is 10° to 60° from stagnation (hot film)<br />Evidence that rotation of baseball delays separation (not confirmed)<br />Magnus effect is only 6.579x10-7 lbs<br />46<br />
- 47. Future Work<br />Lift and lateral forces as function of pressure and humidity<br />Chase Field, Phoenix, Arizona- Lowest humidity<br />Minute Maid Ballpark, Houston, Texas- Highest humidity<br />Fenway Park, Boston, Massachusetts- Highest pressure<br />Coors Field, Denver, Colorado- Lowest pressure<br />Flow visualization<br />Bottom half of the baseball<br />Side of the baseball<br />Ink dot and solvent <br />Confirm that seam delays separation<br />47<br />
- 48. Acknowledgements<br />Advisor: Dr. John Borg<br />Committee Members:<br />Dr. Jon Koch<br />Dr. Phillip Voglewede<br />Machinists:<br />Ray Hamilton<br />Tom Silman<br />Dave Gibas<br />Dr. Robert Nelson at Notre Dame University<br />48<br />
- 49. Questions?<br />49<br />
- 50. BACKUP SLIDES<br />50<br />
- 51. Baseball Setup<br />Holes for baseball were found for each orientation<br />4-seam:<br />Midpoint between seams<br />2-seam: <br />Repeat 4-seam process on each side<br />Midpoint between points was found<br />Checked with distance between seams<br />51<br />
- 52. Baseball Orientation<br />Before any setup was constructed, it was important to configure the direction of the force vectors<br />This was then applied to ELD’s force balance dynamometer<br />52<br />
- 53. Force Balance: Wind Tunnel Setup<br />Design of a peep hole, mirror, and protractor was used to view orientation of baseball<br />53<br />
- 54. Force Balance: Calibration<br />Calibration was done with a series of weights<br />Drawing of lift calibration<br />54<br />
- 55. Force Balance: Apparatus<br />Force balance recorded lift and drag<br />Force balance was rotated to record lift and lateral forces<br />Two different stings were used:<br />Static strut<br />Spinning strut<br />55<br />
- 56. Hot Film Anemometry:<br />Data is mirrored at 180°<br />56<br />
- 57. Hot Film Anemometry:<br />57<br />
- 58. Literature Review<br />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<br />The combination of all three data sets, showing the relationship between all three. (Alaways and Hubbard, 2001)<br />[8] Alaways, L.W. and M. Hubbard, Experimental Determination of Baseball Spin and Lift. Journal of Sports Sciences, 2001. 19: p. 349-358.<br />58<br />
- 59. Force Balance: Magnus Effect<br />Coefficient of Lift, Spin Parameter, is 0.001014<br />59<br />Magnus force is calculated to be 6.579x10-7 lbs, therefore, negligible<br />
- 60. Conclusion: Hot Film Anemometry<br />High shear stress when ball is initially rotating<br />Shear stress causes the baseball to rotate backward<br />60<br />
- 61. Conclusion: Flow Visualization<br />Seams control rotation rate until the pressure recovers over the seam<br />61<br />

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