Seam-shifted wake (SSW) is an aerodynamic phenomenon involving baseballs. The term was coined in 2019 by Andrew Smith during his work on the phenomenon with Barton L. Smith (no relation) at Utah State University (USU). Nazmus Sakib and John Garrett also contributed to the early work.
The USU group showed that Major League Baseball (MLB) baseball seams, when in specific locations relative to the direction of the ball, force the Boundary_layer to separate earlier (closer to the front of the ball) than it normally would. If this occurs on one side of the ball and not on the opposite side, a net force is produced. This force can be similar in magnitude to that caused by spin (i.e. the Magnus effect). [1]
In the particle image velocimetry image shown, the seam on the top of the ball is causing separation (wake formation) on the top closer to the front of the ball than normal. The separation on the bottom of the ball is at the normal location.
The resultant movement from this effect had been noted by others before [2] and named the "laminar effect" based on a mistaken notion that smooth portions of the ball caused a laminar boundary layer more prone to separation than a turbulent boundary layer. This was most often discussed with respect to 2-seam fastballs.
Data from MLB on pitch spin and movement, which were not available in 2019, now make it clear that SSW effects are present in most pitches. [3] Seam effects cause two-seam fastballs and changeups to develop addition arm-side movement as well as sink. Four-seam fastballs can gain extra vertical ride as well as glove-side movement. Certain sliders will "sweep" (or move arm-side) due to seam effects. [4] [5] [6] Some claim benefits from SSW pitches in terms of batter outcomes [7]
Evidence of seam-shifted wake pitches for MLB pitchers can be found by comparing spin-based movement to observed movement on MLB's Spin Leaderboard. [8] These two values being equal indicates no seam-shifted wake, while differences between them (called deviation) are a sign of seam-shifted wake. [3]
Several extensive explanations of how SSW works and what it does to pitches are available. [9] [10]
Laminar flow is the concept of fluid dynamics, consisting of how a fluid is going to follow smooth paths on an object. Laminar flow will occur in areas where the ball is flat, in turn exhibiting no force on that area of the ball. The side where the seams are present will experience Turbulence, and cause a force to act on that side of the ball. In turbulence the air is acting trapped by the seam and pushes the seam out of the way as it moves past it, thus creating a force moving the ball in the opposite direction the seam is present. Most of the effect from the turbulence is on the "back of the ball" or the side that is facing the pitcher after released. [11] The laminar flow from the smooth surface of a baseball makes the air move faster across the surface, and is then caught by the seams and in turn creates the turbulence which in turn makes the ball move.
Examples of SSW through the years
Greg Maddux [12] - Greg Maddux was given a ball that had a scuff on one side. He was known for his knee bending 2-seam, however when he threw this ball he angled the scuff on the left side of the ball inturn giving more movement to the right
Shohei Ohtani- Shohei Ohtani's sweeper was the most valuable sweeper in 2023 based off bWAR and runs prevented. It exhibited 3.8 in of movement above the average sweeper in the league.
Paul Skenes [13] - Paul Skenes splinker was the best pitch in the MLB in 2024 based off avg against. It was a sinker with lower than average spin rate and a different axis allowing more downward movement compared to the average sinker.
Gregory Alan Maddux, also known as "Mad Dog" and "the Professor," is an American former professional baseball pitcher who played 23 seasons in Major League Baseball (MLB), primarily with the Atlanta Braves and Chicago Cubs. He won the 1995 World Series with the Braves over the Cleveland Indians. Maddux was the first pitcher in MLB history to win the Cy Young Award four consecutive years (1992–1995), matched by only one other pitcher, Randy Johnson. During those four seasons, Maddux had a 75–29 record with a 1.98 earned run average (ERA), while allowing less than one baserunner per inning.
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In baseball, a slider is a type of breaking ball, a pitch that moves or "breaks" as it approaches the batter. Due to the grip and wrist motion, the slider typically exhibits more lateral movement when compared to other breaking balls, such as the curveball.
In baseball and softball, the curveball is a type of pitch thrown with a characteristic grip and hand movement that imparts forward spin to the ball, causing it to dive as it approaches the plate. Varieties of curveball include the 12–6 curveball, power curveball, and the knuckle curve. Its close relatives are the slider and the slurve. The "curve" of the ball varies from pitcher to pitcher.
A changeup is a type of pitch in baseball and fastpitch softball.
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In baseball, a circle changeup or circle change is a pitch thrown with a grip that includes a circle formation, hence the name circle changeup. The circle is formed by making a circle with the index finger, holding the thumb at the bottom of the ball parallel to the middle finger and holding the ball far out in the hand. The ball is thrown turning the palm out.
In baseball, a cut fastball or cutter is a type of fastball that breaks toward the pitcher's glove-hand side, as it reaches home plate. This pitch is somewhere between a slider and a four-seam fastball, as it is usually thrown faster than a slider but with more movement than a typical fastball. Some pitchers use a cutter to prevent hitters from expecting their regular fastballs. A common technique for throwing a cutter is to use a four-seam fastball grip with the baseball set slightly off center in the hand. A batter hitting a cutter pitch often achieves only soft contact and an easy out due to the pitch's movement keeping the ball away from the bat's sweet spot. The cutter is typically 2–5 mph slower than a pitcher's four-seam fastball. In 2010, the average pitch classified as a cutter by PITCHf/x thrown by a right-handed pitcher was 88.6 mph; the average two-seamer was 90.97 mph.
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