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Baseball Aerodynamics

The fluid dynamics of baseball pitches

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What Does Boundary Layer Mean? Post #8

Posted on November 25, 2018June 21, 2019 by bartonlsmith

A boundary layer exists whenever a fluid (liquid or gas) flows over a surface.  The boundary layer is the part of the gas that feels the skin of the baseball and is thus accelerated. The concept of the boundary layer was introduced by Ludwig Prandl in 1904.  He is commonly Continue Reading

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PIV On Knuckleball Pitches Post #7

Posted on November 25, 2018December 28, 2019 by bartonlsmith

The “Knuckleball is thrown off the tips of the fingernails in a manner that inhibits spin (or at least when thrown with great skill). As shown in our post on 2-seamers and on one on the seam’s affect on boundary layer, the location of boundary layer separation tends toward the Continue Reading

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What is PIV? Post #6

Posted on November 25, 2018June 21, 2019 by bartonlsmith

Particle Image Velocimetry (PIV) is our main measurement technique.  It uses two laser sheet pulses to illuminate a slice of a flow.  We add particles to the flow (theater fog, in our case), and the laser pulses illuminate these particles. Think of the lasers as a camera flash, but only Continue Reading

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Effect of Seams on the Boundary Layer Post #5

Posted on November 25, 2018June 21, 2019 by bartonlsmith

Our preliminary study using high-seamed Wilson 1030 baseballs and a brutal 3-wheel machine.  These results were presented at the 2018 APS DFD meeting. These results are based on velocity measurements in the air using PIV. All of these data sets were acquired in a vertical plane. We start with a smooth Continue Reading

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Do seams affect trajectory?Post #4

Posted on November 25, 2018November 30, 2020 by bartonlsmith

11/29/2020. I will leave the original post unchanged below, but some of our claims here proved to me untrue, or at least more nuanced than we realized. Were I to write this today, I’d point out that seams don’t matter most of the time when the ball has no gyro Continue Reading

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Attempt using a machine Post #3

Posted on November 25, 2018December 1, 2019 by bartonlsmith

The point here is that, when spinning on the same axis and no gyro, there is no difference between a 2-seam and 4-seam pitch.

Posted In Seam-Shifted Wakes
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