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
PIV On Knuckleball Pitches Post #7
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
What is PIV? Post #6
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
Effect of Seams on the Boundary Layer Post #5
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
Do seams affect trajectory?Post #4
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
Attempt using a machine Post #3
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.