Aerodynamics of a Spinning Table Tennis Ball ~Lift Crisis~

Abstract

The aerodynamic properties of a spinning table tennis ball have been investigated by flight experiments. Using high speed video-cameras, the trajectory and rotation of an official ball (Nittaku 3-Star Premium), which was launched by a three-rotor-machine, were recorded. The drag and lift coefficients (CD and CLZ) were determined by analyzing the videoimages. The measurements cover the speed (Re) and rotation range (SP) of table tennis shots, i.e., 3.0 × 10 4 < Re < 9.0 × 10 4 , 0 < SP < 1.0, and CD and CLZ are obtained as functions of Re and SP. The lift coefficients CLZ is not a monotonic function of SP. A deep valley of CLZ is found around SP=0.5, and the lift force exerted on a spinning ball almost vanishes at Re = 9.0×10 4 and SP = 0.5. In this valley, the standard deviations of CLZ increase drastically, indicating the occurrence of "Lift crisis".

Lift crisis of a spinning table tennis ball

“…In addition, we performed side view analyses at the parameter sets for which no lift force was exerted. We list the results of the accuracy check in table 1, where the previous results given by Tanaka et al (2014) are added for comparison. In general, the obtained lift coefficient C L seems fairly accurate with a small standard deviation.…”

“…The frame rate of the high-speed camera was increased from 3000 fps (Re=3.0−6.0×10 4 ) to 4500 fps (Re=7.0−9.0×10 4 ) as the Reynolds number was increased. This is the second improvement on the previous measurements by Tanaka et al (2014) in which the frame rate was fixed to 1901 fps, irrespective of the Re number. Additionally, we increased the number of data points N in determining the ball trajectory, which was 20 in the measurements by Tanaka et al (2014).…”

“…This is the second improvement on the previous measurements by Tanaka et al (2014) in which the frame rate was fixed to 1901 fps, irrespective of the Re number. Additionally, we increased the number of data points N in determining the ball trajectory, which was 20 in the measurements by Tanaka et al (2014). Here, for the Reynolds number range Re=3.0−5.0×10 4 , N was 50, while N was slightly decreased to N=40 for Re=6.0-9.0×10 4 because the ball reached the board faster.…”

“…From the recorded video image, we could determine the time points (five in total) at which the ball passed these light sheets and hit the acrylic board. It is a major experimental refinement to use light sheets that had narrower widths in comparison with the sheets used in the experiments by Tanaka et al (2014) in which four slit light sheets (8 mm in width) from metal halide lamps were used. The frame rate of the high-speed camera was increased from 3000 fps (Re=3.0−6.0×10 4 ) to 4500 fps (Re=7.0−9.0×10 4 ) as the Reynolds number was increased.…”

“…Moreover, the experimentally determined parameter ranges of the negative Magnus force overlap with those of table tennis shots. By performing free flight experiments, Tanaka et al (2014) tried to confirm the occurrence of a negative Magnus force in actual table tennis games. In their experiments, however, no negative Magnus force was observed in the parameter ranges 2.0×10 4 <Re<9.0×10 4 and 0<SP<1.0, although a deep valley of C L was found around SP=0.5.…”