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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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Journal ArticleDOI
TL;DR: Detailed measurements from a towed mannequin show total drag at the surface is up to 2.4 times the drag when fully immersed, and that to avoid significant wave drag during the underwater sections of starts and turns, swimmers must streamline at depths greater than 1.0m.

153 citations

Journal ArticleDOI
TL;DR: An aerodynamic shape optimization tool for complex industrial flows is developed, based on an hybrid process that couples a stochastic genetic algorithm and a deterministic BFGS hillclimbing method to optimize the rear of a simplified car shape.

153 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-pole representation technique is proposed to represent the object conforming to a natural co-ordinate system in a particle assemblage by a truncated series of multilobular disturbances in which the accuracy of the representation is systematically improved by the addition of higher order multipoles.
Abstract: This paper is the first in a series of investigations having the overall objective of developing a new technique for treating the slow viscous motion past finite assemblages of particles of arbitrary shape. The new method, termed the multi-pole representation technique, is based on the theory that any object conforming to a natural co-ordinate system in a particle assemblage can be approximated by a truncated series of multi-lobular disturbances in which the accuracy of the representation is systematically improved by the addition of higher order multipoles. The essential elements of this theory are illustrated by examining the flows past finite line arrays of axisymmetric bodies such as spheres and spheroids which conform to special natural co-ordinate systems. It is demonstrated that this new procedure converges more rapidly and is simpler to use than the method of reflexions and represents the desired boundaries more precisely than the point-force approximation even when the objects are touching one another. Comparison of these solutions with the exact solutions of Stimson & Jeffery (1926) for the two sphere problem demonstrates the rapidity of convergence of this multipole procedure even when the spheres are touching. Drag results are also presented for flows past chains containing up to 101 spheres as well as for chains containing up to 15 prolate or oblate spheroids. The potential value of the technique is suggested by the rapidity with which the drag calculations were made, the 101 sphere problem requiring about 10 seconds on an IBM 360–65 computer to determine both the fluid flow and the drag coefficient.

153 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that surface sealing is a major factor in controlling cavity formation, and is the factor most responsible for non-Froude scaling of cavity phenomena.
Abstract: High speed motion‐picture studies were made of the dependence of air‐water entry cavities on the relevant physical parameters—in particular, on the atmospheric pressure over the water surface. Experiments on the vertical entry of spheres ¼ in. to 1 in. in diameter, with entrance velocities between 15 ft./sec. and 100 ft./sec., and air pressures between 1/60 atmosphere and 3 atmospheres, show that surface sealing of the cavity is a major factor in controlling cavity formation, and is the factor most responsible for non‐Froude scaling of cavity phenomena. Surface sealing is a function chiefly of the atmospheric density and projectile velocity, although surface tension is also important in its effect on splash formation. Froude's scaling is found to hold true in the region of low Froude's numbers and low atmospheric pressures. The measured average drag coefficient of the projectiles is independent of cavity size and shape. Jets are found to occur regularly and with great strength at both deep and surface closures of the cavity. The observed presence of jets in finite cavities is predicted by an extension of the Kirchhoff‐Helmholtz theory of the infinite (two‐dimensional) cavity to the case of finite cavities with finite cavitation numbers. Some of the results of this theory are mentioned.

153 citations

Journal ArticleDOI
TL;DR: In this paper, an apparatus where individual bubbles are kept stationary in a downward liquid flow was adapted to simultaneously follow mass transfer to/from a single bubble as it inevitably gets contaminated; follow its shape; and periodically measure its terminal velocity.

152 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023307
2022688
2021489
2020504
2019504
2018456