On January 15, 2019, Eric Jagers, Kyle Boddy, Joe Marsh and Dean Jackson of Driveline visited the USU Experimental Fluid Dynamics Laboratory to attempt to capture the air velocity field around a “Laminar Express” pitch. Nazmus Sakib and Andrew Smith (not pictured) took the measurements. These are our preliminary findings.
Our PIV system was housed in a box to prevent any expensive components from being hit. Overall, the setup was very similar to the one described here except the camera was above and the lasers were on the sides, providing a top-view of the ball.
We set the system up with the help of a pitching machine. In the clip below, you can see the ball flying through the measurement system, which is triggered if the ball is in the correct location. Unfortunately, that location was about 10″ X 0.25″, a tough task for the pitchers. Hitting the target had a low probability, but as N goes to infinity, anything can happen. They literally made hundreds of throws.
The video below shows our first successful capture of a laminar express pitch. Note the pitch has a small gyro component (meaning the axis is tilted such that the left side is farther downstream than the right) which allows the seams that surround the smooth side on the left to be more forward (in a more favorable pressure gradient) than a 2-seam without gyro. This smooth side is the laminar side.
The figure below shows a PIV dataset of one Laminar Express pitch. Note that this is viewed from above. We successfully captured 3 Laminar Express pitches during the day. All three showed an important feature: the wake is tilted upward (to the left from the pitcher’s view). In the dataset below, the boundary layer on top appears laminar, in that it separates from the ball near 12 o’clock. On the other hand, on the other side of the ball, the flow is turbulent, and remains attached to the ball far longer. The net result is a tilted wake. The pattern fits my sketch from a month ago. This ball has a downward force on it (in the data frame of reference) which is to the right from the pitcher’s frame of reference. The PIV data near the ball are poor (and there is a large region of missing data at the bottom of the ball), but this does not affect my conclusions.
As a baseline, we decided to also throw balls from the machine at the same speed and with the axis tilted 30 degrees (this was done by tilting the entire machine, strapping it down, and crossing our fingers. I do not recommend using a hack attack this way! The first pitch hit my machinist’s door). A picture of this “setup” is shown below. Note that this machine cannot impart “gyro” spin, which is essential to the laminar express. The spin axis from this machine is always perpendicular to the direction of the ball.
These data were acquired the next day since they do not require a pitcher. We successfully acquired 17 of these pitches. Most had a perfectly symmetric wake, like the pretty one shown below.
On 7 of the 17 pitches from this machine, there was a small tilt of the wake, always upward. An example is shown below. This pitch appears to have some force from laminar flow, but not as much as the pitches with gryo. The tilt could also be from a small amount of Magnus force due to the tilted axis. Furthermore, it does not seem to happen consistently.
Driveline baseball has their own post on this study which as a lot more of the history. It’s excellent stuff.
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