scholarly journals Drag of a cylindrical object in a two-dimensional granular environment

2021 ◽  
Vol 249 ◽  
pp. 03033
Author(s):  
Takumi Kubota ◽  
Haruto Ishikawa ◽  
Satoshi Takada
Keyword(s):  
Angular Dependence ◽  
Drag Force ◽  
Radial Stress ◽  
Packing Fraction ◽  
Dynamic Force ◽  
Two Dimensional ◽  
Collision Model ◽  
Cylindrical Object ◽  
Drag Law ◽  
Yield Force

The drag of a cylindrical object in a two-dimensional granular environment is numerically studied. It is found that the drag law is fitted by the sum of the yield force and the dynamic force, the latter of which is reproduced by a simple collision model. The angular dependence of the radial stress on the surface of the object is given by the Gaussian below the yield force. The probability of the velocity drops of the object is investigated above the yield force, where this probability is independent of the packing fraction and the drag force.

Optimized Driver Placement for Array-Driven Flat-Panel Loudspeakers

2017 ◽  
Vol 42 (1) ◽  
pp. 93-104 ◽  
Author(s):  
David A. Anderson ◽  
Michael C. Heilemann ◽  
Mark F. Bocko
Keyword(s):  
Frequency Band ◽  
Mode Coupling ◽  
Dynamic Force ◽  
Two Dimensional ◽  
Flat Panel ◽  
Piezoelectric Patch ◽  
Optimal Force ◽  
Network Method ◽  
Point Forces ◽  
Bending Modes

Abstract The recently demonstrated ‘modal crossover network’ method for flat panel loudspeaker tuning employs an array of force drivers to selectively excite one or more panel bending modes from a spectrum of panel bending modes. A regularly spaced grid of drivers is a logical configuration for a two-dimensional driver array, and although this can be effective for exciting multiple panel modes it will not necessarily exhibit strong coupling to all of the modes within a given band of frequencies. In this paper a method is described to find optimal force driver array layouts to enable control of all the panel bending modes within a given frequency band. The optimization is carried out both for dynamic force actuators, treated as point forces, and for piezoelectric patch actuators. The optimized array layouts achieve similar maximum mode coupling efficiencies in comparison with regularly spaced driver arrays; however, in the optimized arrays all of the modes within a specified frequency band may be independently addressed, which is important for achieving a desired loudspeaker frequency response. Experiments on flat panel loudspeakers with optimized force actuator array layouts show that each of the panel modes within a selected frequency band may be addressed independently and that the inter-modal crosstalk is typically −30 dB or less with non-ideal drivers.

Jump diffusion in the strong-collision model on a two-dimensional triangular lattice

2014 ◽  
Vol 608 ◽  
pp. 360-365 ◽  
Author(s):  
E. Elkoraychy ◽  
M. Mazroui ◽  
R. Ferrando ◽  
Y. Boughaleb
Keyword(s):  
Triangular Lattice ◽  
Jump Diffusion ◽  
Two Dimensional ◽  
Collision Model

Drag force on a liquid domain moving inside a membrane sheet surrounded by aqueous medium

2015 ◽  
Vol 779 ◽  
pp. 468-482 ◽  
Author(s):  
V. Laxminarsimha Rao ◽  
Sovan Lal Das
Keyword(s):  
Drag Force ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Domain Size ◽  
Bilayer Membrane ◽  
Fredholm Integral Equations ◽  
Two Dimensional ◽  
Liquid Domain ◽  
Viscosity Contrast ◽  
Surrounding Membrane

We compute the drag on a circular and liquid microdomain diffusing in a two-dimensional fluid lipid bilayer membrane surrounded by a fluid above and below. Under the assumptions that the liquids are incompressible and the flow is of low Reynolds number, Stokes’ equations describe the flow in the two-dimensional membrane as well as in the surrounding three-dimensional fluid. The expression for the drag force on the liquid domain involves Fredholm integral equations of the second kind, which we numerically solve using discrete collocation method based on Chebyshev polynomials. We observe that when the domain is more viscous than the surrounding membrane (including the rigid domain case), the drag force is almost independent of the viscosity contrast between the domain and the surrounding membrane, as also observed earlier in experiments by other researchers. The mobility also varies logarithmically with Boussinesq number${\it\beta}$for large${\it\beta}$. On the other hand, for a less viscous domain the dimensionless drag force reduces with increasing viscosity contrast, and a significant change in the drag force, from that when there is no viscosity contrast or when the domain is rigid, has been observed. Further, the logarithmic behaviour of the mobility no longer holds for less viscous domains. Our method of computing the drag force and diffusion coefficient is valid for arbitrary viscosity contrast between the domain and membrane and any domain size (subject to${\it\beta}\geqslant 5$).

scholarly journals Can Drag Force Suppress Fermi Acceleration in a Bouncer Model?

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Francys Andrews de Souza ◽  
Lucas Eduardo Azevedo Simões ◽  
Mário Roberto da Silva ◽  
Edson D. Leonel
Keyword(s):  
Drag Force ◽  
Average Velocity ◽  
Classical Particle ◽  
Nonlinear Mapping ◽  
Sufficient Condition ◽  
Two Dimensional ◽  
Control Parameters ◽  
Fermi Acceleration ◽  
Moving Wall ◽  
Dynamical Properties

Some dynamical properties for a bouncer model—a classical particle of massmfalling in the presence of a constant gravitational fieldgand hitting elastically a periodically moving wall—in the presence of drag force that is assumed to be proportional to the particle's velocity are studied. The dynamics of the model is described in terms of a two-dimensional nonlinear mapping obtained via solution of the second Newton's law of motion. We characterize the behavior of the average velocity of the particle as function of the control parameters as well as the time. Our results show that the average velocity starts growing at first and then bends towards a regime of constant value, thus confirming that the introduction of drag force is a sufficient condition to suppress Fermi acceleration in the model.

scholarly journals How Computational Grid Refinement in Three Dimensions Affects Computational Fluid Dynamics-Discrete Element Method Results for Psuedo-Two-Dimensional Fluidized Gas–Solid Beds

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Annette Volk ◽  
Urmila Ghia ◽  
Milind A. Jog
Keyword(s):  
Three Dimensional ◽  
Computational Grid ◽  
Computational Grids ◽  
Two Dimensional ◽  
Grid Refinement ◽  
Computational Cell ◽  
Bed Height ◽  
Study Results ◽  
Bed Thickness ◽  
Drag Law

Computational fluid dynamics (CFD)-discrete element method (DEM) simulations are designed to model a pseudo-two-dimensional (2D) fluidized bed, in which bed thickness is minimal compared to height and length. Predicted bed behavior varies as the simulations are conducted on increasingly refined computational grids. Pseudo-2D simulation results, in which a single computational cell spans the bed thickness, are compared against fully-three-dimensional (3D) simulations results. Both pseudo-2D and fully-3D simulations exhibit high accuracy when sufficiently refined. Indicators of bed behavior, such as bed height, bed height fluctuation, bubble generation frequency, and segregation, do not appear to converge as the cell size is reduced. The Koch-Hill and Gidaspow drag laws are alternately employed in the simulations, resulting in different trends of results with computational grid refinement. Grid refinement studies are used to quantify the change in results with grid refinement for both three-dimensional, uniform refinement, and for two-dimensional refinement on pseudo-2D computational grids. Grid refinement study results indicate the total drag converges as the computational grid is refined, for both 3D and pseudo-2D approaches. The grid refinement study results are also used to distinguish the relatively grid-independent results using the Koch-Hill drag law from the highly grid-dependent Gidaspow drag law results. Computational cell size has a significant impact on CFD-DEM results for fluidized beds, but the grid refinement study method can be used to quantify the resulting numerical error.

Rigid intruder inside a two-dimensional dense granular flow: Drag force and cavity formation

2013 ◽  
Vol 87 (3) ◽  
Author(s):  
Evelyne Kolb ◽  
Pierre Cixous ◽  
Niels Gaudouen ◽  
Thierry Darnige
Keyword(s):  
Drag Force ◽  
Granular Flow ◽  
Cavity Formation ◽  
Two Dimensional ◽  
Dense Granular Flow ◽  
Flow Drag
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