Sound waves and the absence of Galilean invariance in flocks
نویسنده
چکیده
We study a model of flocking for a very large system (N=320,000) numerically. We find that in the long wavelength, long time limit, the fluctuations of the velocity and density fields are carried by propagating sound modes, whose dispersion and damping agree quantitatively with the predictions of our previous work using a continuum equation. We find that the sound velocity is anisotropic and characterized by its speed c for propagation perpendicular to the mean velocity < ~v >, < ~v > itself, and a third velocity λ < ~v >, arising explicitly from the lack of Galilean invariance in flocks. Typeset using REVTEX
منابع مشابه
On the Galilean Invariance of Some Dispersive Wave Equations
Surface water waves in ideal fluids have been typically modeled by asymptotic approximations of the full Euler equations. Some of these simplified models lose relevant properties of the full water wave problem. One of these properties is the Galilean symmetry, i.e. the invariance under Galilean transformations. In this paper, a mechanism to incorporate Galilean invariance in classical water wav...
متن کاملCan Special Relativity Be Derived from Galilean Mechanics Alone?
Special relativity is based on the apparent contradiction between two postulates, namely, Galilean vs. c-invariance. We show that anomalies ensue by holding the former postulate alone. In order for Galilean invariance to be consistent, it must hold not only for bodies’ motions, but also for the signals and forces they exchange. If the latter ones do not obey the Galilean version of the Velociti...
متن کاملEffects of Sound Stimulation on Physiological and Biochemical Responses of ‘Salvia splendens’
Plants are influenced inevitably by environmental stresses due to their immobility. Sound waves are one of these environmental factors affecting plants. This study was designed to understand the relationship between sound waves and plant responses that is still low knowledge. For this purpose, Salvia splendens, one of the common plants in urban green spaces, were influenced by sound wa...
متن کاملLattice Boltzmann algorithms without cubic defects in Galilean invariance on standard lattices
The vast majority of lattice Boltzmann algorithms produce a non-Galilean invariant viscous stress. This defect arises from the absence of a term in the third moment, the equilibrium heat flow tensor, proportional to the cube of the fluid velocity. This moment cannot be specified independently of the lower moments on the standard lattices such as D2Q9, D3Q15, D3Q19 or D3Q27. A partial correction...
متن کامل2 00 4 Investigation of Galilean Invariance of multi - phase lattice Boltzmann methods
We examine the Galilean invariance of standard lattice Boltzmann methods for two-phase fluids. We show that the known Galilean invariant term that is cubic in the velocities, and is usually neglected, is the main source of Galilean invariance violations. We show that incorporating a correction term can improve the Galilean invariance of the method by up to an order of magnitude. Surprisingly in...
متن کامل