Figure 2 - uploaded by James Andrew Scobie
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Conventional swing (CS) of a cricket ball (boundary layer greatly exaggerated for clarity) as shown from above.
Source publication
A cricket ball has an encircling, stitched seam proud from the leather, separating the surface into two distinct hemispheres. When angled, this seam is exploited by the skilful bowler to create an asymmetry in the viscous boundary layer and the ball will swing. In this article, the fluid dynamics of both conventional swing and reverse swing are exp...
Contexts in source publication
Context 1
... relatively recent review of cricket ball swing was published by Mehta. 9 CS is well understood and illustrated in Figure 2 10 with the encircling primary seam inclined at an angle to the flow. The fluid-dynamic boundary layer separates from the surface of the ball as it experiences an adverse pressure gradient. ...
Context 2
... ball will wear and roughen as the match progresses, causing natural transition to turbulent flow -there is turbulent flow on both sides, so the asymmetry and swing are lost as the ball ages with play. During the course of play, the fielding side will vigorously polish the ball to maintain this smooth condition and prolong the period where swing is effective -the polished side opposite the seam is marked in Figure 2. On a sunny day, the sun will warm the wicket and generate micro-turbulence, 11 which may disturb the laminar flow and transform it to turbulence -hence swing tends to happen on cloudy days, not sunny days. ...
Citations
... The cause of conventional new ball swing has been extensively studied by wind tunnel researchers (R. D. Mehta, 1985;Scobie et al., 2013Scobie et al., , 2020. Releasing the ball with the primary seam in an upright and angled orientation creates airflow asymmetry ( Figure 1). ...
... Within scientific literature, authors have hypothesised the causes of late swing R. D. Mehta, 2005;Scobie et al., 2013Scobie et al., , 2020. One suggestion is that bowlers release the ball with a velocity just above the critical threshold required to trip the boundary layer on the non-seam side of the ball. ...
... One suggestion is that bowlers release the ball with a velocity just above the critical threshold required to trip the boundary layer on the non-seam side of the ball. Initially, both sides will be surrounded by turbulent boundary layers, but as the ball slows during flight, the non-seam side transitions to laminar airflow (R. D. Mehta, 2005;Scobie et al., 2020). Another suggestion is a shifting seam orientation during flight whereby backspin imparted on the ball at release creates gyroscopic inertia to stabilise the axis of rotation and seam position Scobie et al., 2013Scobie et al., , 2020. ...
... Vitally for the relationship between cricket and climate change, this gameplay is strongly influenced by the natural environment in which it is situated. A cricket ball is leather with a pronounced seam, which makes it able to move laterally or 'swing' in the air, an effect that is heavily influenced by environmental conditions (Scobie et al. 2020). The hardness of this ball also makes extensive and bulky protective equipment necessary, from helmets to gloves and leg pads. ...
... Since the 1970s, researchers have measured swing force using cricket balls mounted on a sting in a wind tunnel. Results showing C S against Re for new cricket balls, from Scobie et al. (2020), Deshpande, Shakya & Mittal (2018), Sayers & Hill (1999) and Alam et al. (2010b) are reproduced in figure 6. Old balls, which have been worn through use in a cricket match (Scobie et al. 2013Tadrist et al. 2020) or aged artificially using sandpaper (Deshpande et al. 2018), have also been investigated and results from these experiments are shown in figure 7. Included in both figures are measurements performed for this review paper which are labelled 'W'. ...
... Reproduced from Achenbach (1974). Research by Achenbach (1972Achenbach ( , 1974 into the flow past spheres is referenced in several cricket ball swing papers (Bentley 1982;Scobie et al. 2013Scobie et al. , 2020Jackson et al. 2020;Tadrist et al. 2020) and figure 10 reproduces Achenbach's results showing separation angle plotted against Reynolds number for spheres with three levels of roughness. For the smooth sphere, the separation point in the sub-critical regime where Re < 2 × 10 5 is 82 • . ...
... This increases to around 120 • in the super-critical regime where Re > 4 × 10 5 . Scobie et al. (2020) combine their cricket ball measurements with Achenbach's results for spheres, to provide an explanation of conventional swing which is illustrated by the sketch in figure 11. To validate Scobie et al.'s description of conventional swing, IR images of the non-seam and seam sides of a new cricket ball, at Re values which result in conventional swing, have been captured at the Whittle Laboratory in Cambridge, UK. ...
This paper reviews 70 years of cricket ball swing literature and reassesses the results in light of new measurements. A comparison of ball tracking data with published experimental results shows that current understanding does not explain the behaviour observed in professional cricket matches. Descriptions of cricket ball boundary layer aerodynamics are updated with new results which show that the seam acts more like a series of vortex generators than a trip and that there is a laminar separation bubble on the seam side of the ball. Previous results for reverse swing are consolidated and compared with new data, showing that different magnitudes of swing occur depending on the condition of both sides of the ball. Variation in pressure and temperature should be included when the Reynolds number, a non-dimensional ball speed, is calculated, while humidity can be neglected. Studies on the effect of wind speed and direction are summarised and results considering the effect of free-stream turbulence are compared with new measurements. Throughout the paper, recommendations for future work are suggested. These include quantitative study of the effect of surface defects and roughness, an assessment of whether atmospheric turbulence can affect swing and investigation into the effect of backspin on swing.
... Bowlers must release the ball in a way that the seam remains stable and upright (see Figure 4) throughout flight to maximise swing. This is achieved when the seam appears in a fixed vertical position and maintains constant airflow asymmetry surrounding the ball to cause swing (Barton, 1982;Bentley et al., 1982;Scobie et al., 2020). To maintain seam stability, the participants suggested imparting backspin on the ball at release, which corresponds with existing literature (Barton, 1982;Lindsay & Spratford, 2020;R. ...
... By creating late swing, batters have less time to make correct decisions about what shot to play and consequently, late swing is considered more difficult to face than early swing (Club, 1952). Within scientific literature, late swing has been suggested to be caused by the ball reaching optimal characteristics late in flight, such as a decrease in speed (Barton, 1982;Scobie et al., 2020). However, there are currently no in situ studies that have investigated late swing and further research is required (Lindsay & Spratford, 2020). ...
... Red balls are produced using dye and lacquer and are said to swing for a greater number of overs compared to white and pink balls that have paint applied to the surface that easily deteriorates. The two most widely used brands are Kookaburra and Dukes, with Dukes balls reported to have a more pronounced primary seam, a smaller secondary seam and a more durable lacquer (Rundell, 2009;Scobie et al., 2020). Researchers have reported that these factors allow Dukes balls to swing at higher speeds, to a greater magnitude, and for more deliveries when compared to Kookaburra balls (Scobie et al., 2020), corresponding with the findings of this study. ...
... Justham et al., , 2008L. M. Justham et al., 2010;Mehta et al., 2022;Phillips et al., 2012;Scobie et al., 2020). This study will attempt to identify specifically which bowling variations aid bowlers fulfil one of their main objectives (preventing the concession of runs) during what is perceived to be the most difficult time to bowl, the "death phase". ...
... A somewhat surprising result obtained in this study is that bowling variations were not revealed to be significantly associated with the concession of runs. Lateral movements, such as swing bowling and seam bowling, have been previously revealed as effective skills for a bowler to possess in order to fulfil their broad objectives of taking wickets and preventing the concession of runs (Mehta et al., 2022;Phillips et al., 2012;Scobie et al., 2013Scobie et al., , 2020. Furthermore, other bowling variations that are frequently bowled by skilled bowlers such as the "slower ball" or "cutter" deliveries are also known to aid general bowling performance (Feros et al., 2019;L. ...
In this study, 3,767 balls bowled by international-level fast bowlers across two One-Day International (ODI) tournaments were analysed to determine how to effectively bowl during the “death” phase of an innings (final 10 overs). The results of chi-squared analyses revealed that bowling length, bowling line, batter quality and having wickets in hand were all associated with the concession of runs during the death phase (all p < 0.001). Specifically, the yorker length is revealed to be very effective at restricting runs conceded, whereas the opposite is true for the half-volley and full-toss lengths. The batting side having five or more wickets in hand results in greater than expected runs being scored during the death phase. Furthermore, the results reveal that middle order batters score more runs than their tail-ender team-mates during this death phase, suggesting that middle-order batters have to assume the role of “finishers”. From a practical perspective, the results of this study clearly identify areas bowlers can target to constrict the scoring of runs as well as areas they should avoid. Batting strategies in the death phase should consist maintaining five or more wickets in hand and thereby not exposing tail-enders to the bowling attack.
... This study did have some limitations. Firstly, no data were available on weather conditions, which can impact levels of swing and spin for bowlers (Jamil et al., 2021;Petersen, 2017;Scobie et al., 2020) and thus potentially impact the batters' striking abilities. Second, information regarding whether the ball was delivered by the bowler from over the wicket or around the wicket was also lacking and this alteration of bowling angles could therefore have also affected the distribution of the ball post batting connection. ...
This study examined 503 power-hitting strokes that resulted in the maximum of 6-runs being scored in international men’s one-day and T20 cricket. Chi-Squared analyses were conducted to determine if performance and situational variables were associated with the distribution (direction) of aerial power-hitting strokes. Results revealed that bowling length, bowling line, bowler type and powerplays were all significantly (p < 0.001) associated with ball-hitting distribution. Post-hoc analysis of the standardised residuals revealed that greater than expected 6ʹs were scored behind square and were associated with short-pitched bowling, fast bowling and the power-play. Similarly, bowling the half-volley length and the outside off line resulted in greater than expected 6ʹs on the off-side. The results suggest that bowlers should try to avoid offering width outside the off stump as well as bowling the half-volley and short-pitched lengths as these bowling lines and lengths present batters with greater opportunities to score maximum runs. Fast bowling is revealed to be more susceptible to power-hitting strokes than spin bowling. Conversely, batters may wish to target the areas behind square or on the off-side for opportunities to score maximum runs, and they should look to take full advantage of the powerplay field restrictions.
... In fulfiling their objectives, they often develop a repertoire of skills which consist of inducing swing movement and seam movement or deliberately varying their bowling speed (Edwards & Beaton, 1996;Laura Justham et al., 2006;L. M. Justham et al., 2010;Phillips et al., 2012;Scobie et al., 2020). ...
... In cricket, the main tactic used by bowlers to outfox (and subsequently bring about an error) in a batter's performance is to make the ball deviate away from a straight-line trajectory somewhere between the delivery of the ball to when the ball arrives at the batter (Edwards & Beaton, 1996). This is why fast bowlers will often attempt to make the ball "swing" which consists of curving the trajectory of the ball's flight path, ultimately making it more difficult for the batter to make contact with the ball (Phillips et al., 2010;Scobie et al., 2020). Swing bowling generally exists in two forms, conventional swing, which tends to occur in the opening overs of an innings with a new (and shiny) ball and reverse swing, which skilful bowlers can induce after roughly 30 overs, provided the bowling team has carefully manipulated the surface of the ball (Scobie et al., 2013). ...
... Swing bowling generally exists in two forms, conventional swing, which tends to occur in the opening overs of an innings with a new (and shiny) ball and reverse swing, which skilful bowlers can induce after roughly 30 overs, provided the bowling team has carefully manipulated the surface of the ball (Scobie et al., 2013). Conventional swing consists of in-swinging and outswinging deliveries, which will move in towards the bat, or away from the bat, respectively, whilst reverse swing causes the ball to move in the opposite directions (Scobie et al., 2020). Both forms of swing bowling require skill and experience, particularly as the bowler has to bowl the ball in excess of 80 mile/h (35.8 m per second) and also impart some backspin on the ball through their bowling action in order to stabilise the seam as a wobbling seam would result in no swing (Scobie et al., 2013(Scobie et al., , 2020. ...
In this study, 13,176 balls bowled by international level fast bowlers were analysed in order to investigate the relationship between the types of delivery and their effectiveness. The results of Chi-Squared analyses revealed significant associations between the type of delivery and runs conceded (p < 0.001) as well as wickets taken (p < 0.001). Seam movement was revealed to be more effective than swing bowling at both producing dot balls and taking wickets. Specifically, balls that 'seam-away" were revealed to be the most effective for bowling dots and "seam-in" for taking wickets. The "away-swinger" resulted in significantly greater than expected dot balls as did the "in-swinger" but only the in-swinger resulted in significantly greater than expected wickets. Both the "off-cutter" and "slower-balls" were revealed to result in significantly fewer than expected dot balls but significantly greater than expected wickets, implying bowlers must assess for themselves the risk versus reward of these two types of variation. Balls with no-movement were revealed to have no significant relationship with runs conceded, but did result in significantly fewer than expected wickets. Evidence suggests that lateral movement is crucial to bowling success with seam movement revealed to be more effective than swing.
... CS is well understood, and several articles provide a detailed explanation [3,4]. An illustration of the boundary layer profiles for this case are shown in Figure 1b. ...
... In practice, cricket balls are imperfect spheres with manufacturing irregularities and an inherent surface roughness, which are exacerbated as the ball ages and wears. Direct side force measurements on new and aged stationary Dukes cricket balls in a wind tunnel by Scobie et al. [4] are presented in Figure 3 as a function of Re. Note that Scobie et al. [4,5] investigated an extensive series of balls aged under first-class match conditions and provided Achenbach later investigated the effect of surface roughness on the separation angles of spheres [8]. ...
... Direct side force measurements on new and aged stationary Dukes cricket balls in a wind tunnel by Scobie et al. [4] are presented in Figure 3 as a function of Re. Note that Scobie et al. [4,5] investigated an extensive series of balls aged under first-class match conditions and provided Achenbach later investigated the effect of surface roughness on the separation angles of spheres [8]. He found that the value of Re in the critical regime reduces with increasing roughness, as the roughness destabilizes the boundary layer and causes it to transition to turbulence earlier. ...
Lateral movement from the principal trajectory, or "swing", can be generated on a cricket ball when its seam, which sits proud of the surface, is angled to the flow. The boundary layer on the two hemispheres divided by the seam is governed by the Reynolds number and the surface roughness; the swing is fundamentally caused by the pressure differences associated with asymmetric flow separation. Skillful bowlers impart a small backspin to create gyroscopic inertia and stabilize the seam position in flight. Under certain flow conditions, the resultant pressure asymmetry can reverse across the hemispheres and "reverse swing" will occur. In this paper, particle image velocimetry measurements of a scaled cricket ball are presented to interrogate the flow field and the physical mechanism for reverse swing. The results show that a laminar separation bubble forms on the non-seam side (hemisphere), causing the separation angle for the boundary layer to be increased relative to that on the seam side. For the first time, it is shown that the separation bubble is present even under large rates of backspin, suggesting that this flow feature is present under match conditions. The Magnus effect on a rotating ball is also demonstrated, with the position of flow separation on the upper (retreating) side delayed due to the reduced relative speed between the surface and the freestream.
... Above median bowlers had significantly lower release speeds for inswing (28.6 compared to 31.0 m·s −1 ) and outswing (29.8 compared to 31.7 m·s −1 ), correlating with studies suggesting swing decreases above a critical velocity (Bentley et al., 1982;Mehta et al., 1983;Mehta & Koga, 2000;Mehta & Wood, 1980;Scobie et al., 2019). Furthermore, seam azimuth angles were greater in AM bowlers for both inswing (32.4°compared to 21.7°) and outswing (22.3°compared to 17.4°), correlating with studies suggesting closer to 30°is beneficial for lower speeds (Barton, 1982;Bentley et al., 1982;Mehta et al., 1983). ...
... A further limitation was only capturing the first three metres of ball flight. The possibility of late swing has been discussed, where the ball follows a straight flight path before swinging just prior to bounce, believed to be caused by reaching optimal ball kinematics late in flight (Barton, 1982;Scobie et al., 2019), although no research substantiates these claims. Finally, while the dynamic markers were attached flat on the balls, they may have caused boundary layer transition earlier on the nonseam side of the ball, reducing airflow asymmetry and swing, similar to what is seen in older and rougher balls (Scobie et al., 2019). ...
... The possibility of late swing has been discussed, where the ball follows a straight flight path before swinging just prior to bounce, believed to be caused by reaching optimal ball kinematics late in flight (Barton, 1982;Scobie et al., 2019), although no research substantiates these claims. Finally, while the dynamic markers were attached flat on the balls, they may have caused boundary layer transition earlier on the nonseam side of the ball, reducing airflow asymmetry and swing, similar to what is seen in older and rougher balls (Scobie et al., 2019). ...
When executed correctly, swing bowling has the potential to influence the outcome of a cricket match, yet little is known about the required bowling action and ball flight characteristics. This study aimed to describe the bowling action and initial ball flight characteristics as well as to identify variables that may be associated with increased swing in pathway and high-performance medium and fast pace bowlers. A 17-camera Vicon motion analysis system captured retro-reflective markers placed on the upper-body of participants and new cricket balls to quantify bowling action and initial ball flight kinematics. Bowlers delivered the ball with their forearm and hand angled in the direction of intended swing with an extended wrist flexing through the point of ball release. Bowlers who produced more swing had increased seam stability, possibly linked to a lower wrist and ball angular velocity. It is believed that swing increases with seam stability, however, optimal ranges may exist for seam azimuth angle, ball angular velocity and release speed. These findings may assist coaches to optimise the performance of bowlers, however, future research should use bowlers who play at higher levels to investigate swing bowling at greater speeds.
... Although cricket ball aerodynamics has been largely discussed [6,7,11,16,17], game conditions to produce contrast or reverse swing, Fig. 1b and c, have never been analysed quantitatively except in Scobie et al. [14,18]. We propose here to examine the contrast swing technique's dependence on ball roughness by using both experimental and theoretical approaches. ...
Curved trajectories are widely used in sports played with balls. Specifically, in cricket, balls are bowled with curved trajectories to surprise the batsman. Amongst the bowling techniques that provide curved trajectories, one of the most controversial is called contrast swing. This technique is specific to cricket and happens when the ball gets nonuniform wear on each hemisphere after a few launches. The differential wear on the two sides of the cricket ball creates an aerodynamic side force. We quantify this force through wind tunnel experiments varying the roughness on one hemisphere of the ball. Trajectory modelling shows that this aerodynamic force is consistent with measurements on real throws. We also measure the side-to-side differential wear generated on a cricket ball as a function of the number of launches. Finally, we estimate the minimum velocity required to achieve contrast swing and the expected deviation as a function of launches number and game conditions.
