scholarly journals Particle dispersion processes in two-dimensional turbulence: a comparison with 2-D kinematic simulation.

2007 ◽  
Vol 14 (2) ◽  
pp. 139-151 ◽  
Author(s):  
R. Castilla ◽  
J. M. Redondo ◽  
P. J. Gámez-Montero ◽  
A. Babiano
Keyword(s):  
Turbulent Flows ◽  
Particle Dispersion ◽  
Space Time ◽  
Relative Dispersion ◽  
Kinematic Simulation ◽  
Space Time Structure ◽  
Coherent Vortices ◽  
The One ◽  
Turbulent Particle Dispersion ◽  
Kinematic Simulations

Abstract. We study numerically the comparison between Lagrangian experiments on turbulent particle dispersion in 2-D turbulent flows performed, on the one hand, on the basis of direct numerical simulations (DNS) and, on the other hand, using kinematic simulations (KS). Eulerian space-time structure of both DNS and KS dynamics are not comparable, mostly due to the absence of strong coherent vortices and advection processes in the KS fields. The comparison allows to refine past studies about the contribution of non-homogeneous space-time 2-D Eulerian structure on the turbulent absolute and relative particle dispersion processes. We particularly focus our discussion on the Richardson's regime for relative dispersion.

An Improved Eddy Interaction Model for Numerical Simulation of Turbulent Particle Dispersion

1996 ◽  
Vol 118 (4) ◽  
pp. 819-823 ◽  
Author(s):  
D. I. Graham
Keyword(s):  
Turbulent Flows ◽  
Interaction Model ◽  
Particle Dispersion ◽  
Solid Particles ◽  
Experimental Investigations ◽  
Time Step ◽  
Limiting Behavior ◽  
Stationary Turbulence ◽  
Low Concentrations ◽  
Turbulent Particle Dispersion

Three main effects have been observed in experimental investigations of the dispersion of low concentrations of solid particles in homogeneous turbulent flows, namely the crossing trajectories, inertia, and continuity effects. This paper discusses the development of a simple Lagrangian eddy interaction model to account for all three of these effects. By choosing the length, time, and velocity scales in the model so as to be consistent with the corresponding scales in homogeneous, isotropic, and stationary turbulence, the proper limiting behavior is ensured both for fluid particles and for heavy solid particles. Because only one time step is required per eddy, the computational efficiency of the model is ensured.

On the Space-Time Local Active Control

1997 ◽  
Vol 16 (2) ◽  
pp. 89-108 ◽  
Author(s):  
Vladimir V. Arabadzhi
Keyword(s):  
Active Control ◽  
Time Scale ◽  
Space Time ◽  
One Dimensional ◽  
Control Approach ◽  
Space Time Structure ◽  
Time Region ◽  
Alternative Approaches ◽  
Active Wave ◽  
The One

The traditional active control approach includes the following steps: (1) measuring of the wave field; (2) extracting (identification) of total space-time structure of the wave to be damped fro the data measured; (3) generating of the cancelling wave i.e. the one inverted with respect to the wave to be damped. This paper is devoted to the searching of alternative approaches, when we can produce the damping wave without knowledge of the structure of the wave to be damped or make active wave damping without damping wave at all. Four algorithms (approaches) are proposed below for the space one-dimensional active damping problem. These algorithms ensure the solution operating in the sapce-time region of a scale much less than the minimum space-time scale of the wave to be damped i.e. this control is local in space and time.

Space-time structure of auroral radio absorption events observed with the imaging riometer at south pole

Radio Science ◽  
1991 ◽  
Vol 26 (4) ◽  
pp. 925-930 ◽  
Author(s):  
J. K. Hargreaves ◽  
D. L. Detrick ◽  
T. J. Rosenberg
Keyword(s):  
Space Time ◽  
Time Structure ◽  
South Pole ◽  
Space Time Structure

scholarly journals Simulations of Nearshore Particle-Pair Dispersion in Southern California

2013 ◽  
Vol 43 (9) ◽  
pp. 1862-1879 ◽  
Author(s):  
Leonel Romero ◽  
Yusuke Uchiyama ◽  
J. Carter Ohlmann ◽  
James C. McWilliams ◽  
David A. Siegel
Keyword(s):  
Kinetic Energy ◽  
Southern California ◽  
Separation Distance ◽  
Horizontal Resolution ◽  
Particle Dispersion ◽  
Eddy Kinetic Energy ◽  
Relative Dispersion ◽  
Numerical Resolution ◽  
Relative Diffusivity ◽  
Pair Separation

Abstract Knowledge of horizontal relative dispersion in nearshore oceans is important for many applications including the transport and fate of pollutants and the dynamics of nearshore ecosystems. Two-particle dispersion statistics are calculated from millions of synthetic particle trajectories from high-resolution numerical simulations of the Southern California Bight. The model horizontal resolution of 250 m allows the investigation of the two-particle dispersion, with an initial pair separation of 500 m. The relative dispersion is characterized with respect to the coastal geometry, bathymetry, eddy kinetic energy, and the relative magnitudes of strain and vorticity. Dispersion is dominated by the submesoscale, not by tides. In general, headlands are more energetic and dispersive than bays. Relative diffusivity estimates are smaller and more anisotropic close to shore. Farther from shore, the relative diffusivity increases and becomes less anisotropic, approaching isotropy ~10 km from the coast. The degree of anisotropy of the relative diffusivity is qualitatively consistent with that for eddy kinetic energy. The total relative diffusivity as a function of pair separation distance R is on average proportional to R5/4. Additional Lagrangian experiments at higher horizontal numerical resolution confirmed the robustness of these results. Structures of large vorticity are preferably elongated and aligned with the coastline nearshore, which may limit cross-shelf dispersion. The results provide useful information for the design of subgrid-scale mixing parameterizations as well as quantifying the transport and dispersal of dissolved pollutants and biological propagules.

scholarly journals SPACE–TIME STRUCTURE AND SPINOR GEOMETRY

2008 ◽  
Vol 50 (2) ◽  
pp. 143-176 ◽  
Author(s):  
GEORGE SZEKERES ◽  
LINDSAY PETERS
Keyword(s):  
Cosmological Solution ◽  
Space Time ◽  
Time Structure ◽  
Variation Principle ◽  
Field Equations ◽  
Covering Group ◽  
Space Time Structure ◽  
Spinor Geometry ◽  
Complete Set ◽  
Particle Solution

AbstractThe structure of space–time is examined by extending the standard Lorentz connection group to its complex covering group, operating on a 16-dimensional “spinor” frame. A Hamiltonian variation principle is used to derive the field equations for the spinor connection. The result is a complete set of field equations which allow the sources of the gravitational and electromagnetic fields, and the intrinsic spin of a particle, to appear as a manifestation of the space–time structure. A cosmological solution and a simple particle solution are examined. Further extensions to the connection group are proposed.

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