Referenzen
- Vorführexperimente, Videos
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Coins Dropped Into Crystal Clear Water: A View From The Bottom As The Coins Sink. Ogemaw Springs, MI
simple presentation of the phenomenom
- Wissenschaftliche Artikel
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Chaotic dynamics of falling disks
They report experimental observations of the dynamics of disks falling in water/glycerol mixtures. They find four distinct types of motion, which are mapped out in a ‘phase diagram’. The complex behaviour can be reduced to a series of one-dimensional maps, which display a discontinuity at the crossover from periodic to chaotic motion.
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Coins falling in water
When a coin falls in water, its trajectory is one of four types determined by its dimensionless moment of inertia and Reynolds number: steady, fluttering, chaotic or tumbling. The dynamics induced by the interaction of the water with the surface of the coin, however, makes the exact landing site difficult to predict a priori. Here, they describe a designed experiment in which a coin is dropped repeatedly in water to determine the probability density functions associated with the landing positions for each of the four trajectory types,
all of which are radially symmetric about the centre drop-line. -
Falling styles of disk
They numerically investigate the dynamics of thin disks falling under gravity in a viscous fluid medium at rest at infinity. Varying independently the density and thickness of the disk reveals the influence of the disk aspect ratio. They observe the four types of planar regimes already reported in experiments but also identify two additional fully three-dimensional
regimes in which the body experiences a slow horizontal precession superimposed onto zigzagging or tumbling motions. -
Holes stabilize freely falling coins
This paper investigates experimentally the falling dynamics of thin discs with central holes. The effects of the central hole on the disc’s motion is characterized for a range of Reynolds number, moment of inertia, and inner to outer diameter ratio.
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Kinematics and wake of f reely falling cylinders at moderate Reynolds numbers
They investigate experimentally the motion of elongated finite-length cylinders freely falling under the effect of buoyancy in a low-viscosity fluid otherwise at rest. A dedicated image processing algorithm was implemented to properly reconstruct the position and orientation of the cylinders in the three-dimensional space.
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On the numerical simulation of the unsteady free fall of a solid in a fluid: I. The Newtonian case
They present a numerical method for the simulation of the instationary free fall of a unique solid in a fluid. A key ingredient of the proposed approach is the reformulation of the conservation and kinetic equations in the solid frame as well as the explicit treatment of the fluid-body coupling. Numerical experiments for the steady-falling regime, for the periodic oscillating motion as well as for the tumbling motion are presented following existing experimental set-up. The proposed method is validated by comparison with experimental data.
https://www.sciencedirect.com/science/article/pii/S0045793007000746
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Plate falling in a fluid: Regular and chaotic dynamics of finite-dimensional models
Results are reviewed concerning the planar problem of a plate falling in a resisting medium studied with models based on ordinary differential equations for a small number of dynamical variables. A unified model is introduced to conduct a comparative analysis of the dynamical behaviors of various models using common dimensionless variables and parameters.
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Thin disks falling in air
They experimentally investigate the settling of millimetre-sized thin disks in air. Physical parameters are varied: the diameter-to-thickness aspect ratio, the Reynolds numbers based on the disk diameter and fall speed and the inertia ratio. Thousands of trajectories are reconstructed for each disk type by planar high-speed imaging. Larger fall speeds (and, thus, smaller drag coefficients) are found with respect to existing correlations based on experiments in liquids, demonstrating the role of the density ratio in setting the vertical velocity.
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Unsteady aerodynamics of fluttering and tumbling plates
They investigate the aerodynamics of freely falling plates in a quasi-two-dimensional flow at Reynolds number of 103 , which is typical for a leaf or business card falling in air. They quantify the trajectories experimentally using high-speed digital video at sufficient resolution to determine the instantaneous plate accelerations and thus to deduce the instantaneous fluid forces. They compare the measurements with direct numerical solutions of the two-dimensional Navier–Stokes equation.
https://dragonfly.tam.cornell.edu/publications/2005_JFM_Andersen_Pesavento_Wang_a.pdf
- Bücher
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Flow Around a Cylinder
University lecture notes including Matlab Codes and lecture videos.
https://www.math.hkust.edu.hk/%7Emachas/flow-around-a-cylinder.pdf
- Online-Ressourcen
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Flow around a disk (or an infinite cylinder)
Derivation and presentation of a Matlab/GNU Octave script, which can be used to plot the figures of the streamlines, the equipotentials and the pressure field of the flow around a disk (or an infinite cylinder).
https://apmr.matelys.com/BasicsMechanics/Fluid/FlowAroundADisk.html
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Flutter and tumble in fluids
Journal article explaining the phenomenon