Topic
Drag coefficient
About: Drag coefficient is a research topic. Over the lifetime, 14471 publications have been published within this topic receiving 303196 citations. The topic is also known as: drag factor.
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TL;DR: In this paper, the aerodynamic properties and boundary-layer dynamics of a soccer ball are not yet well understood; however, it is possible that a "knuckle-ball effect" of the non-rotating ball played a role in this phenomenon.
Abstract: When the boundary layer of a sports ball undergoes the transition from laminar to turbulent flow, a drag crisis occurs whereby the drag coefficient (C
d) rapidly decreases. However, the aerodynamic properties and boundary-layer dynamics of a soccer ball are not yet well understood. In this study we showed that the critical Reynolds number (Re
crit) of soccer balls ranged from 2.2 × 105 to 3.0 × 105. Wind-tunnel testing, along with visualisation of the dynamics of the boundary layer and the trailing vortex of a ball in flight, demonstrated that both non-spinning and spinning (curved) balls had lowC
d values in the super-critical region. In addition, theRe
crit values of the soccer balls were lower than those of smooth spheres, ranging from ∼ 3.5 × 105 to 4.0 × 105, due to the effects of their panels. This indicated that the aerodynamic properties of a soccer ball were intermediate between those of a smooth ball and a golf ball. In a flow visualisation experiment, the separation point retreated and theC
d decreased in a super-critical regime compared with those in a sub-critical regime, suggesting a phenomenon similar to that observed in other sports balls. With some non-spinning and spinning soccer balls, the wake varied over time. In general, the high-frequency component of an eddy dissipated, while the low-frequency component increased as the downstream vortex increased. The causes of the large-scale fluctuations in the vortex observed in the present study were unclear; however, it is possible that a ‘knuckle-ball effect’ of the non-rotating ball played a role in this phenomenon.
121 citations
TL;DR: In this article, two or three spheres were set up in a water tunnel in the longitudinal or transverse direction with Reynolds numbers less than 10 3, and the flow behind the sphere was visualized by the use of condense milk and change in vortex structure due to the interaction was observed in detail.
121 citations
TL;DR: Lu et al. as discussed by the authors investigated the effects of particle properties on these meso-scale structures, for all particle types, two-fluid modeling with and without consideration of mesoscale structures were performed and compared.
120 citations
TL;DR: In this article, the dislocation drag coefficient of aluminum single crystals was measured by the strain rate method at 10°K, 77°K and 300°K with a maximum shear strain rate of 2.6 × 104sec−1.
120 citations
TL;DR: In this paper, the cross-flow drag and normal force coefficients are determined experimentally as a function of the relative displacement of fluid in time-dependent two-dimensional flow, and the evolution with time of the body-wake characteristics are determined from high-speed motion pictures.
Abstract: The analogy between the impulsive flow over circular cylinders and flat plates and the separated flow about slender bodies moving at high angles of attack in the subsonic to moderately supersonic-velocity range is discussed. The cross-flow drag and normal force coefficients are determined experimentally as a function of the relative displacement of fluid in time-dependent two-dimensional flow. The evolution with time of the body-wake characteristics are determined from high-speed motion pictures. The results show that during the growth of symmetrical vortices, the laminar flow drag coefficients of the test bodies reach a value about 25% higher than their corresponding steady flow values. In the supercritical range, records for the drag show considerable disagreement, except that the drag coefficient lies between 0.25 and 0.40.
120 citations