共查询到20条相似文献,搜索用时 15 毫秒
1.
Sergiu C. Dragomir Matthew Sinnott Eren S. Semercigil Özden F. Turan 《Journal of sound and vibration》2012,331(5):963-973
A study on the energy dissipation characteristics of granular materials flowing/sloshing in a rotating container is presented here. The objective is to develop a configuration for control of excessive structural oscillations, similar to those of tuned vibration absorbers and tuned sloshing absorbers. The effectiveness of energy dissipation through granular flow is primarily determined experimentally. A computational model is developed to understand the flow behavior and energy dissipation in this system. A promising kinematic match of the particle behavior is demonstrated between the numerical predictions and the experimental observations. The use of the granular flow in a rotating drum for vibration control is being investigated for the first time. 相似文献
2.
《Physica A》2002,303(1-2):48-56
We considered a flow of a cohesionless granular material in a partially filled three-dimensional rotating container. A variational continuum mechanics model is suggested to describe the profile of the free surface of the granular material. A combination of a level set method and a variational form of energy conservation equation allows us to describe flow of granular material in arbitrary-shaped containers. 相似文献
3.
Experimental and numerical study on energy dissipation in freely cooling granular gases under microgravity 下载免费PDF全文
Energy dissipation is one of the most important properties of granular gas, which makes its behavior different from that of molecular gas. In this work we report our investigations on the freely-cooling evolution of granular gas under microgravity in a drop tower experiment, and also conduct the molecular dynamics(MD) simulation for comparison.While our experimental and simulation results support Haff's law that the kinetic energy dissipates with time t as E(t) ~(1 + t/τ)~(-2), we modify τ by taking into account the friction dissipation during collisions, and study the effects of number density and particle size on the collision frequency. From the standard deviation of the measured velocity distributions we also verify the energy dissipation law, which is in agreement with Haff's kinetic energy dissipation. 相似文献
4.
5.
The nonequilibrium fluctuations of power flux in a fluidized granular media have been recently measured in an experiment [Phys. Rev. Lett. 92, 164301 (2004)], which was announced to be a verification of the fluctuation relation (FR) by Gallavotti and Cohen. An effective temperature was also identified and proposed to be a useful probe for such nonequilibrium systems. We explain these results in terms of a two-temperature Poisson process. Within this model, supported by independent molecular dynamics simulations, power flux fluctuations do not satisfy the FR and the nature of the effective temperature is clarified. In the pursuit of a hypothetical global quantity fulfilling the FR, this points to the need of considering candidates other than the power flux. 相似文献
6.
Using the lubrication approximation we investigate two-dimensional steady flow of a thin film of fluid with temperature-dependent
viscosity on a uniformly heated or cooled horizontal cylinder, which may be stationary or rotating about its axis, in the
case when the Biot number (a measure of heat transfer at the free surface) is large.We show that the film thickness (but not
the fluid velocity) may be obtained from that in the isothermal case by a simple re-scaling. 相似文献
7.
We derive the motion energy dissipation model to investigate the relation between the additional energy loss of vehicles and the slope of a gradient. Simulations are carried out to check the validity of the dissipation model. Analysis of the results shows that the total energy consumption is inversely proportional to the slope in an uphill situation and the opposite conclusion can be drawn in a downhill situation. The energy dissipation rate depends on the density of traffic and the road length in two situations in a rule. It is found that the simulation result is in good agreement with real traffic. 相似文献
8.
R. Bouakkaz K. Talbi Y. Khelil F. Salhi N. Belghar M. Ouazizi 《Thermophysics and Aeromechanics》2014,21(1):87-97
The heat transfer and air flow around an unconfined heated rotating circular cylinder is investigated numerically for varying rotation rates (α = 0–6) in the Reynolds number range of 20–200. The numerical calculations are carried out by using a finite volume method based commercial computational fluid dynamics solver FLUENT. The successive changes in the flow pattern are studied as a function of the rotation rate. Suppression of vortex shedding occurs as the rotation rate increases (α > 2). A second kind of instability appears for higher rotation speed where a series of counter-clockwise vortices is shed in the upper shear layer. The rotation attenuates the secondary instability and increases the critical Reynolds number for the appearance of this instability. Besides, time-averaged (lift and drag coefficients and Nusselt number) results are obtained and compared with the literature data. A good agreement has been obtained for both the local and averaged values. 相似文献
9.
Stenflo L. Yu M.Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(2):104-105
Previous work on exact cylindrical surface waves in a nonneutral cold-electron plasma bounded by a dielectric is extended to include plasma rotation. A set of nonlinear rate equations describing the temporal behavior of the system is derived by first determining an appropriate spatial wave structure. Physically relevant periodic solutions are obtained 相似文献
10.
11.
The fully 3D turbulent incompressible flow around a cylinder and in its wake at a Reynolds number Re = = 9×104 based on the cylinder diameter and Mach number M = 0.1 is calculated using Large Eddy Simulations (LES). Encouraging results are found in comparison to experimental data for the fluctuating lift and drag forces. The acoustic pressure in far-field is commutated through the surface integral formulation of the Ffowcs Williams and Hawkings (FWH) equation in acoustic analogy. Five different sound sources, the cylinder wall and four permeable surfaces in the flow fields, are employed. The spectra of the sound pressure are generally in quantitative agreement with the measured one though the acoustic sources are pseudo-sound regarding the incompressible flow simulation. The acoustic component at the Strouhal number related to vortex shedding has been predicted accurately. For the broad band sound, the permeable surfaces in the near wake region give qualitative enough accuracy level of predictions, while the cylinder wall surface shows a noticeable under-prediction. The sound radiation of the volumetric sources based on Lighthill tensors at vortex shedding is also studied. Its far-field directivity is of lateral quadrupoles with the weak radiations in the flow and cross-flow directions. 相似文献
12.
13.
14.
The dynamics of granular material discharging from a cuboid but thin hopper,including the hopper flow and granular jet,are investigated via discrete element method(DEM)simulations.The slot width is varied to study its influence on the flow.It is found the flow in the cuboid hopper has similarity with the flow in two-dimensional(2D)hopper.When the slot width is large,the flowrate is higher than the predicted value from Beverloo’s law and the velocity distribution is not Gaussian-like.For granular jet,there is a transition with varying slot width.For large slot width,there is a dense core in the jet and the variations of velocities and density are relatively small.Finally,the availability of continuum model is assessed and the results show that the performance with large slot width is better than that with small slot width. 相似文献
15.
16.
A rotating suspension of nonbuoyant particles can develop striking inhomogeneities in particle concentration, with regular bands of high and low concentration along the symmetry axis. We report Stokes-flow simulations showing that the formation of axial bands is correlated with an inhomogeneous particle distribution in the radial plane. An order parameter, based on the average angular velocity of the particles, characterizes two distinct phases: a low-frequency segregated phase and a high-frequency dispersed phase. The axial band structure develops during the transition between these two phases. 相似文献
17.
18.
19.
Experimental data show that the efficiency of an irradiation process, ε, of the flowing water is related to water flowrate. In this work, we introduce a new formula for water flowrate which parameters ε and dose distribution well related to the flowrate are derived, analytically. First, in terms of stream velocity, electron fluence is defined then, the accepted concepts of an electron beam irradiation processing are rewritten in flowrate dependence using the experimental data of ε versus flowrate and initial electron energy. The final formula predicts the depth-dose distributions respect to the flowrate. Also, we propose an analytical formula for D(t) and further for Fe and ε in terms of the flowrate with definition of C1 parameter as a correlation factor of velocity on the surface and in the bulk. Further, the simulation approach shows flowrate dependence of the depth-dose curve well. 相似文献
20.
A. Salhi M. Omri 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):463-475
An analysis based on the available experimental data and second-order closures is made for a turbulent shear flow over a rotating
cylinder in a quiescent fluid. The near-wall behaviour of the non-linear model for the pressure-strain correlation proposed
by Speziale, Sarkar and Gatski [J. Fluid Mech. 245, 227 (1991)] is enlarged; and the methodology proposed by Lai and So [J. Fluid Mech. 221, 641 (1990)] is adopted to take into account the wall-effects. The radial profile of the curvature parameter, Rs, is examined in connection with the logarithmic law. It is shown that the log-layer is associated to the region where the
mean velocity profile, V, is related to the power of the radial distance as Computations reveal that this region corresponds to the state with the most destabilizing curvature effects; which can be
chararacterized by the minimum value of the parameter B
c
=2R
s
(1+2R
s
), and not that one of the parameter B=2R
s
(1+2R
s
)/(1+R
s
)2 firstly introduced by Bradshaw [J. Fluid Mech. 36, 171 (1969)] and extensively used to characterize the turbulence structure in curved flows.
Received 9 December 1997 相似文献