LARGE-SCALE VORTICAL STRUCTURES PRODUCED BY AN IMPINGING DENSITY JET IN SHALLOW CROSSFLOW

The large-scale vortical structures produced by an impinging density jet in shallow crossflow were numerically investigated in detail using RNG turbulence model. The scales, formation mechanism and evolution feature of the upstream wall vortex in relation to stagnation point and the Scarf vortex in near field were analyzed. The computed characteristic scales of the upstream vortex show distinguished three-dimensionality and vary with the velocity ratio and the water depth. The Scarf vortex in the near field plays an important role in the lateral concentration distributions of the impinging jet in crossflow. When the velocity ratio is relatively small, there exists a distinct lateral high concentration aggregation zone at the lateral edge between the bottom layer wall jet and the ambient crossflow, which is dominated by the Scarf vortex in the near field.

INFLUENCE OF LARGE-SCALE VORTICAL STRUCTURES ON THE PARTICLE DISPERSION IN A PLANE MIXING LAYER

The present study considers the developing mixing layer that is formed bymerging of two free streams initially separated by a splitter plate. To investigate the influence ofthe vortical structures on the particle dispersion, numerical simulation was conducted when thevelocity ratio, defined as R = U_∞ - U_(-∞)/U_∞ + U_(-∞), is 0. 5. Large-Eddy Simulation (LES)was employed to understand the effect of large-scale vortical structures originated by theKelvin-Helmholtz instability on the partical dispersion. The flyash with the particle sizes 10, 50,100, 150, and 200um respectively were loaded at the origin of the two-dimensional mixing layer. Itis confirmed that the particle dispersion depends strongly on the motion of large-scale vorticalstructures. The particle dispersion is visualized numerically by following the particle trajectoriesin the mixing layer undergoing pairing interaction.

Galaxy Interactions in Filaments and Sheets:Effects of the Large-scale Structures Versus the Local Density

Major interactions are known to trigger star formation in galaxies and alter their color.We study the major interactions in filaments and sheets using SDSS data to understand the influence of large-scale environments on galaxy interactions.We identify the galaxies in filaments and sheets using the local dimension and also find the major pairs residing in these environments.The star formation rate(SFR) and color of the interacting galaxies as a function of pair separation are separately analyzed in filaments and sheets.The analysis is repeated for three volume limited samples covering different magnitude ranges.The major pairs residing in the filaments show a significantly higher SFR and bluer color than those residing in the sheets up to the projected pair separation of~50 kpc.We observe a complete reversal of this behavior for both the SFR and color of the galaxy pairs having a projected separation larger than 50 kpc.Some earlier studies report that the galaxy pairs align with the filament axis.Such alignment inside filaments indicates anisotropic accretion that may cause these differences.We do not observe these trends in the brighter galaxy samples.The pairs in filaments and sheets from the brighter galaxy samples trace relatively denser regions in these environments.The absence of these trends in the brighter samples may be explained by the dominant effect of the local density over the effects of the large-scale environment.

Neutrino Mass Constraints from Reconstructing the Large-scale Structure:Systematic Uncertainty

We examine the possibility of applying the baryonic acoustic oscillation reconstruction method to improve the neutrino massΣm_νconstraint.Thanks to the Gaussianization of the process,we demonstrate that the reconstruction algorithm could improve the measurement accuracy by roughly a factor of two.On the other hand,the reconstruction process itself becomes a source of systematic error.While the algorithm is supposed to produce the displacement field from a density distribution,various approximations cause the reconstructed output to deviate on intermediate scales.Nevertheless,it is still possible to benefit from this Gaussianized field,given that we can carefully calibrate the“transfer function”between the reconstruction output and theoretical displacement divergence from simulations.The limitation of this approach is then set by the numerical stability of this transfer function.With an ensemble of simulations,we show that such systematic error could become comparable to statistical uncertainties for a DESI-like survey and be safely neglected for other less ambitious surveys.

Experimental and numerical investigations on the vortical structures of an impinging jet in crossflow

The objective of this dissertation is to investigate the impinging jet under the influence of crossflow. It has been known that there exist jet shear layer, impingement on the bottom wall, interactions between the induced wall jet and the ambient crossflow in near field. There are few intensive studies of the impinging jet in crossflow at home and abroad due to the complexities of flow, such as the formation and evolution of the vortical structures, interactions among vortices, while researches on the temporal and spatial evolution of these vortical structures can promote the practical applications in environment engineering, hydroelectricity engineering, etc., and provide the basis for flow control and improvement through revealing the inherent mechanism and development of the vortical structures.

Alignment between galaxies and large-scale structure

Based on the Sloan Digital Sky Survey DR6 （SDSS） and the ＇Millennium Simulation （MS）, we investigate the alignment between galaxies and large-scale structure. For this purpose, we develop two new statistical tools, namely the alignment correlation function and the cos（20）-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy catalog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous （L 〉 ～L＊） galaxies out to projected separations of 60 h-lMpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos（2θ）-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo （with size similar to that of the stellar galaxy）. As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of -25°. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for cen- tral galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference galaxy distribution to be flat- tened parallel to the orientations of red luminous galaxies with axis ratios of -0.5 and ,-0.75 for halo and central orientations, respectively. These ratios are almost independent of scale out to 60 h^-1 Mpc.

A Summary of the Large-Scale Access Convergence Network Structure

Under the requirement of everything over IP, network service shows the following characteristics:(1) network service increases its richness;(2) broadband streaming media becomes the mainstream. To achieve unified multi-service bearing in the IP network, the largescale access convergence network architecture is proposed. This flat access convergence structure with ultra-small hops, which shortens the service transmission path, reduces the complexity of the edge of the network, and achieves IP strong waist model with the integration of computation, storage and transmission. The key technologies are also introduced in this paper, including endto-end performance guarantee for real time interactive services, fog storing mechanism, and built-in safety transmission with integration of aggregation and control.

Dynamics of Secondary Large-Scale Structures in ETG Turbulence Simulations

The dynamics of secondary large-scale structures in electron-temperature-gradient （ETG） turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.

Free-Interface Dual-Compatibility Modal Synthesis Substructure Method in Large-Scale Structures

Free-interface dual-compatibility modal synthesis method(compatibility of both force and displacement on interfaces)is introduced to large-scale civil engineering structure to enhance computation efficiency. The basic equations of the method are first set up, and then the mode cut-off principle and the dividing principle are proposed. MATLAB is used for simulation in different frame structures. The simulation results demonstrate the applicability of this substructure method to civil engineering structures and the correctness of the proposed mode cut-off principle. Studies are also conducted on how to divide the whole structure for better computation efficiency while maintaining better precision. It is observed that the geometry and material properties should be considered, and the synthesis results would be more precise when the inflection points of the mode shapes are taken into consideration. Furthermore, the simulation performed on a large-scale high-rise connected structure further proves the feasibility and efficiency of this modal synthesis method compared with the traditional global method. It is also concluded from the simulation results that the fewer number of DOFs in each substructure will result in better computation efficiency, but too many substructures will be time-consuming due to the tedious synthesis procedures. Moreover, the substructures with free interface will introduce errors and reduce the precision dramatically, which should be avoided.

Fast SSED-MoM /FEM Analysis for Electromagnetic Scattering of Large-Scale Periodic Dielectric Structures

A hybrid method combining simplified sub-entire domain basis function method of moment with finite element method( SSED-MoM /FEM) is accelerated for electromagnetic( EM) scattering analysis of large-scale periodic structures.The unknowns are reduced sharply with non-uniform mesh in FEM. The computational complexity of the hybrid method is dramatically declined by applying conjugate gradient-fast Fourier transform( CG-FFT) to the integral equations of both electric field and magnetic field. The efficiency is further improved by using OpenMP technique. Numerical results demonstrate that the SSED-MoM /FEM method can be accelerated for more than three thousand times with large-scale periodic structures.

Probing the Large-scale Structure of the Universe Through Gravitational Wave Observations

The improvements in the sensitivity of the gravitational wave(GW) network enable the detection of several large redshift GW sources by third-generation GW detectors. These advancements provide an independent method to probe the large-scale structure of the universe by using the clustering of the binary black holes(BBHs). The black hole catalogs are complementary to the galaxy catalogs because of large redshifts of GW events, which may imply that BBHs are a better choice than galaxies to probe the large-scale structure of the universe and cosmic evolution over a large redshift range. To probe the large-scale structure, we used the sky position of the BBHs observed by third-generation GW detectors to calculate the angular correlation function and the bias factor of the population of BBHs. This method is also statistically significant as 5000 BBHs are simulated. Moreover, for the third-generation GW detectors, we found that the bias factor can be recovered to within 33% with an observational time of ten years. This method only depends on the GW source-location posteriors;hence, it can be an independent method to reveal the formation mechanisms and origin of the BBH mergers compared to the electromagnetic method.

Empirical Analysis of Relationship between Farmers'Income Structure and Consumption in Guizhou Province in the Context of Large-scale Poverty Alleviation

Large-scale poverty alleviation is one of the three major strategic actions of Guizhou Province to plan for leapfrog development.Through building an econometric model,this paper made an empirical analysis of relationship between farmers'income structure and consumption in Guizhou Province in the context of large-scale poverty alleviation.The results show that the wage income and transfer income of rural residents in Guizhou Province have a significant impact on the promotion of their consumption,and the impact of income from household business operation is also significant,but the impact is relatively weak,while the contribution of farmers'property income to their consumption is insufficient.Finally,in view of the problems in the relationship between the income structure and consumption of farmers in Guizhou Province,it came up with policy recommendations including broadening the income channels,increasing farmers'income,improving the income structure,and promoting farmers'consumption.

Large-Scale Structure Formation via Quantum Fluctuations and Gravitational Instability

This is a review of the status of the universe as described by the standard cosmological model combined with the inflationary paradigm. Their key features and predictions, consistent with the WMAP (Wilkinson Microwave Anisotropies Probe) and Planck Probe 2013 results, provide a significant mechanism to generate the primordial gravitational waves and the density perturbations which grow over time, and later become the large-scale structure of the universe—from the quantum fluctuations in the early era to the structure observed 13.7 billion later, our epoch. In the single field slow-roll paradigm, the primordial quantum fluctuations in the inflaton field itself translate into the curvature and density perturbations which grow over time via gravitational instability. High density regions continuously attract more matter from the surrounding space, the high density regions become more and more dense in time while depleting the low density regions. At late times the highest density regions peaks collapse into the large structure of the universe, whose gravitational instability effects are observed in the clustering features of galaxies in the sky. Thus, the origin of all structure in the universe probably comes from an early era where the universe was filled with a scalar field and nothing else.

On the Large-Scale Structure of the Universe as given by the Voronoi Diagrams

The size distributions of 2D and 3D Voronoi cells and of cells of Vp（2, 3）,--2D cut of 3D Voronoi diagram--are explored, with the slngle-parameter （re-scaled） gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp（2, 3） map with galaxies lying on the cell boundaries is constructed to compare, as regards general appearance, with the observed CfA map of galaxies and voids, the parameters of the simulation being so chosen as to reproduce the largest observed void size.

Formation of Nonlinear Solitary Vortical Structures by Coupled Electrostatic Drift and Ion-Acoustic Waves

Propagation of coupled electrostatic drift and ion-acoustic waves（DIAWs） is presented. It is shown that nonlinear solitary vortical structures can be formed by low-frequency coupled electrostatic DIAWs. Primary waves of distinct（small, intermediate and large） scales are considered. Appropriate set of 3 D equations consisting of the generalized Hasegawa-Mima equation for the electrostatic potential（involving both vector and scalar nonlinearities） and the equation of motion of ions parallel to magnetic field are obtained. According to experiments of laboratory plasma mainly focused to large scale DIAWs, the possibility of self-organization of DIAWs into the nonlinear solitary vortical structures is shown analytically. Peculiarities of scalar nonlinearities in the formation of solitary vortical structures are widely discussed.

Super-Large-Scale Structures in the Sloan Digital Sky Survey

We study the super-large-scale structures in the Sloan Digital Sky Survey by cluster analysis, and examine the geometry and the properties of the member galaxies. Two subsamples are selected from the SDSS, Subsample 1 at the celestial equator and Subsample 2 further north. In Subsample 1 we discover two compact super-large-scale structures： the Sloan Great Wall and the CfA Great Wall. The Sloan Great Wall, located at a median redshift of z= 0.07804, has a total length of about 433 Mpc and a mean galaxy density of about six times that of the whole sample. Most of its member galaxies are of medium size and brightness. The CfA Great Wall, located at a median redshift of z = 0.03058, has a total length of about 251 Mpc and includes large percentages of faint and small galaxies and relatively fewer early-type galaxies.

Observational Features of Large-Scale Structures as Revealed by the Catastrophe Model of Solar Eruptions

Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material through a series of equilibrium configurations. The motion brings energy into the coronal magnetic field until the system ceases to be in equilibrium. The catastrophe theory for solar eruptions indicates that loss of mechanical equilibrium constitutes the main trigger mechanism of major eruptions, usually shown up as solar flares, eruptive prominences, and coronal mass ejections （CMEs）. Magnetic reconnection which takes place at the very beginning of the eruption as a result of plasma instabilities/turbulence inside the current sheet, converts magnetic energy into heating and kinetic energy that are responsible for solar flares, and for accelerating both plasma ejecta （flows and CMEs） and energetic particles. Various manifestations are thus related to one another, and the physics behind these relationships is catastrophe and magnetic reconnection. This work reports on recent progress in both theoretical research and observations on eruptive phenomena showing the above manifestations. We start by displaying the properties of large-scale structures in the corona and the related magnetic fields prior to an eruption, and show various morphological features of the disrupting magnetic fields. Then, in the framework of the catastrophe theory, we look into the physics behind those features investigated in a succession of previous works, and discuss the approaches they used.

Geostructures, dynamics and risk mitigation of high-altitude and long- runout rockslides

Long-runout rockslides at high altitude could cause disaster chain in river basins and destroy towns and major infrasturctures.This paper firstly explores the initiation mechanism of high-altitude and long-runout rockslides.Two types of sliding-prone geostructure models,i.e.the fault control type in orogenic belt and the fold control type in platform area,are proposed.Then,large-scale experimental apparatus and associated numerical simulations are conducted to understanding the chain-style dynamics of rockslide-debris avalanche-debris flow.The results reveal the fragmentation effects,the rheological behaviors and the boundary layer effect of long-runout avalanche-debris flow.The dynamic character-istics of quasi-static-transition-inertia state and solid-liquid coupling in rapid movement of rockslide-debris avalanche-debris flow are investigated.Finally,the risk mitigation strategy of the non-structure and structure for resilient energy dissipation are illustrated for initiation,transition and deposition zones.The structural prevention and mitigation methods have been successfully applied to the high-altitude and long-runout rockslides in Zhouqu and Maoxian of the Wenchuan earthquake zone,as well as the other major geohazards in Qinghai-Tibet Plateau and its adjacent areas.

CFD Simulation of Flow Features and Vorticity Structures in Tuna-Like Swimming

The theoretical research on the propulsive principle of aquatic animal becomes more important and attracted more researchers to make efforts on it. In the present study, a computational fluid dynamic （CFD） simulation of a three-dimensional traveling-wave undulations body of tuna has been developed to investigate the fluid flow features and vorticity structures around this body when moving in a straight line. The undulation only takes place in the posterior half of the fish, and the tuna-tail is considered as a lunate fin oscillating with the mode combined swaying with yawing. A Reynolds-averaged Navier-Stokes （RANS） equation is developed, employing a control-volume method and a k-omega SST turbulent model; meanwhile an unstructured tetrahedral grid, which is generated for the three-dimensional geometry, is used based on the deformation of the hind parts of the body and corresponding movement of the tail. We calculated the hydrodynamic performance of tuna-like body when a tuna swims in a uniform velocity, and compared the input power coefficient, output power coefficient and propulsive efficiency of the oscillating tuna-tail with or without body vortex shedding. Additionally, the load distribution on the body, flow features and vorticity structures around the body were demonstrated. The effect of interaction between the body-generated vortices and the tail-generated vorticity on the hydrodynamic performance can be obtained.

Effect of the Interaction of Different Scale Vortices on the Structure and Motion of Typhoons

Five numerical experiments have been performed in this paper by using a quasigtostrophic barotropical model to investigate the interaction of different scale vortiCes on the structure and motion of typhoons.Results show that this interaction may arouse the irregular changes of the asymmetric structure of typhoons,thus leading to anomalous Phenomena such as meandering tracks and sudden changes in the motion speed of typhoons;the ￣t Of this interaction on the strucure and motion may be quite different when the smaller vortex is situated in different Posihons of the typhoon circulation.