Seam-Shifted Wake (SWW) is a phenomenon that describes how certain seam orientations on a pitch can impact the symmetry of airflow being displaced around the ball.
This results in unbalanced forces affecting the ball, which is referred to as a “Seam-Shifted Wake.” A pitch that contains Seam-Shifted Wake moves differently than we’d expect a pitch of the same variety to move.
In essence, SSW is a concept that describes movement profiles of pitches that move differently compared to what their measurable metrics such as Spin Axis, arm slot, and release point would estimate.
You may have seen pitches that exhibit “late movement” and seem to jump or move at the last possible second as they reach the plate. These pitches might be examples of balls impacted by SSW, where they display movement that’s atypical based on their pitch metrics.
Measurement
Having different seam orientations is part of what creates varying aerodynamic and seam-shifted wake effects. The “wake” of a pitch is the path that the displaced air takes as it moves around and behind the ball. Think of the flow of water behind a speedboat, the wake created in the water by the boat is the same wake created in the air by a pitch.
The raised seams on an otherwise smooth baseball disrupt the airflow around the ball at certain orientations, which causes an asymmetrical wake behind the ball. This ultimately leads to uneven drag forces acting on the ball, which can result in atypical “late movement.”
Source: 1.A. W. Smith and B. L. Smith, “Using Baseball Seams to Alter a Pitch Direction: The Seam Shifted Wake,” Journal of Sports Engineering and Technology, p.1754337120961609, 2020
Much of the research and data completed on the existence of Seam-Shifted Wake and its impact on movement has been done by Dr. Barton Smith, so make sure to check out his website (baseballaero.com) for more information on the topic.
Understanding the concept of SSW and what may affect a thrown baseball is essential because there are unknown factors that we have yet to uncover as it pertains to pitch flight and movement.
Summary
Seam-Shifted Wake is a novel concept in the area of pitch design, gaining traction with players and coaches seeking to enhance pitching performance. Understanding what SSW is and how it plays a role in pitch movement is helpful in learning why pitches move the way they do.
Related Links
Baseball Aerodynamics – The fluid dynamics of baseball pitches
https://www.baseballaero.com/2021/04/11/the-cubs-and-seam-shifted-wake-post-70/
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