From Flutter to Tumble: Inertial Drag and Froude Similarity in Falling Paper

Belmonte, Andrew; Eisenberg, Henryk; Moses, Elisha

doi:10.1103/physrevlett.81.345

Cited by 152 publications

(193 citation statements)

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“…In the past decade there has been a revival of interest in the tumbling motion exhibited by extended objects as they fall through air [1,2]. These complex motions are of a different nature than what we study here.…”

Section: Introductionmentioning

confidence: 59%

Chiral sedimentation of extended objects in viscous media

2009

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We study theoretically the chirality of a generic rigid object's sedimentation in a fluid under gravity in the low Reynolds number regime. We represent the object as a collection of small Stokes spheres or stokeslets, and the gravitational force as a constant point force applied at an arbitrary point of the object. For a generic configuration of stokeslets and forcing point, the motion takes a simple form in the nearly free draining limit where the stokeslet radius is arbitrarily small.In this case, the internal hydrodynamic interactions between stokeslets are weak, and the object follows a helical path while rotating at a constant angular velocity ω about a fixed axis. This ω is independent of initial orientation, and thus constitutes a chiral response for the object. Even though there can be no such chiral response in the absence of hydrodynamic interactions between the stokeslets, the angular velocity obtains a fixed, nonzero limit as the stokeslet radius approaches zero. We characterize empirically how ω depends on the placement of the stokeslets, concentrating on three-stokeslet objects with the external force applied far from the stokeslets. Objects with the largest ω are aligned along the forcing direction. In this case, the limiting ω varies as the inverse square of the minimum distance between stokeslets. We illustrate the prevalence of this robust chiral motion with experiments on small macroscopic objects of arbitrary shape.

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Section: Introductionmentioning

confidence: 59%

Chiral sedimentation of extended objects in viscous media

2009

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“…In Appendix A, a movement model for a falling paper strip [TK94,BEM98] is described. This model is based on how thin paper strips move through the air when they are allowed to fall freely.…”

Section: Falling Snowmentioning

confidence: 99%

Parallel Methods for Real-Time Visualization of Snow

Saltvik

Elster

Nagel

Lecture Notes in Computer Science

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In this thesis, we look at the underlying numerical fluid equations for simulation of snow and look at how to optimize and parallelize these routines as well as how to display the results efficiently through OpenGL.Multiprocessor platforms will be considered. The ultimate goal is to acheive near real-time realistic simulations of snow. AbstractUsing computer generated imaging is becoming more and more popular in areas such as computer gaming, movie industry and simulation. A familiar scene in the winter months for most us in the Nordic countries is snow. This thesis discusses some of the complex numerical algorithms behind snow simulations. Previous methods for snow simulation have either covered only a very limited aspect of snow, or have been unsuitable for real-time performance. In this thesis, some of these methods are combined into a model for real-time snow simulation that handles both snowflake motion through the air, wind simulation, and accumulation of snow on objects and the ground.With a goal towards achieving real-time performance with more than 25 frames per second, some new parallel methods for the snow model are introduced. Focus is set on efficient parallelization on new SMP and multi-core computer systems. The algorithms are first parallelized in a pure data-parallel manner by dividing the data structures among threads. This scheme is then improved by overlapping inherently sequential algorithms with computations for the following frame, to eliminate processor idle time. A speedup of 1.9 on modern dual CPU workstations is achieved, while displaying a visually satisfying result in real-time. By utilizing Hyper-Threading enabled dual CPU systems, the speedup is further improved to 2.0. i

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“…Mahadevan et al [19] relate experimentally the tumbling frequency with the dimensions (length l, width w and thickness t) of rectangular cards which satisfy the relationship l w t trying, in this way, to eliminate three dimensional effects. In 1998, Belmonte et al [20] studied the transition from fluttering to tumbling in a quasi-two-dimensional experiment in which flat strips were dropped in a narrow container filled with fluid (water, glycerol/water or petroleum ether) and mechanical constraints ensured the twodimensional plate motion. Further improvements were done by Andersen et al [21] who eliminated the mechanical constrained and used a release mechanism for dropping the aluminium plates.…”

Section: -mentioning

confidence: 99%