General

Some of these may not mean a lot to lay persons. I’m putting this here so I can keep my eye on the ball and in case anyone like-minded wanders by. As these questions are answered, I’ll change them to italics and link the answer to the Yes or No. Continue Reading

Here’s a very nice description of transition from laminar to turbulent flow and how that is distinct from yet often correlated to boundary layer separation. This may help you better understand my description of how seams and pressure gradients interact as well as how that may lead to the Laminar Continue Reading

OK, this is some hardcore fluid dynamics. Hang on tight. But understanding this concept is key to understanding how seams may effect laminar/turbulent flow and boundary layer separation. As a baseball moves through the air, the pressure on the front of the ball is higher than the surrounding air, which Continue Reading

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

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

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

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

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

RPP tackled the same question (why 2 and 4-seam fastballs are different) back in July and came to the same conclusion (that seam orientation in itself does nothing) but from the opposite direction.  They showed that a 4-seam pitch with side-spin induced at release would run the same way as Continue Reading