Mesoscale Structure of Rainstorm Retrieved from Dual-Doppler Radar Observations Using the 4DVAR Assimilation Technique

The four-dimensional variational （4DVAR） data assimilation method was applied to dual-Doppler radar data about two Meiyu rainstorms observed during CHeRES （China Heavy Rain Experiment and Study）. The purpose of this study is to examine the performance of the 4DVAR technique in retrieving rainstorm mesoscale structure and to reveal the feature of rainstorm mesoscale structure. Results demonstrated that the 4DVAR assimilation method was able to retrieve the detailed structure of wind, thermodynamics, and microphysics fields from dual-Doppler radar observations. The retrieved wind fields agreed with the dual- Doppler synthesized winds and were accurate. The distributions of the retrieved perturbation pressure, perturbation temperature, and microphysics fields were also reasonable through the examination of their physical consistency. Both of the two heavy rainfalls were caused by merging cloud processes. The wind shear and convergence lines at middle and lower levels were their primary dynamical characteristics. The convective system was often related to low-level convergence and upper-level divergence coupled with up- drafts. During its mature stage, the convective system was characterized by low pressure at lower level and high pressure at upper level, associated with warmer at middle level and colder at lower and upper levels than the environment. However, a region of cooling and high pressure occurred in the lower and middle levels compared to warming and low pressure in the upper level during its dissipating ＇.stage. The water vapor, cloud water, and rainwater corresponded to the convergence, the updraft and the intensive reflectivity, respectively.

Particle clustering(mesoscale structure)of high-flux gas-solid circulating fluidized bed

Particle clustering is an important dynamic phenomenon in circulating-fluidized-bed(CFBs)systems,and has been suggested as a key contributing factor to the non-uniform hydrodynamics of CFBs.Studies show that particle clusters can be affected by solids flux,in terms of frequency,duration,and solids holdup.To understand the characteristics of particle clusters under high-solids-flux conditions,experimental and modeling studies in high-solids-flux gas-solids CFBs were reviewed and summarized.Optical and electrical measurements and imaging methods were used to monitor the particle-clustering phenomenon in CFBs.Particles were found to cluster in high-flux CFBs,and were characterized by a denser cluster-solids holdup and a shorter time fraction,which was different from the behavior in low-flux CFBs.Particle properties affected particle clustering in high-flux CFBs significantly.In modeling work,Eulerian-Eulerian and Eulerian-Lagrangian methods were used to study the particle-cluster characteristics.Good results can be obtained by using the Eulerian-Eulerian method to simulate the CFB system,especially the high-flux CFBs,and by considering the effects of particle clusters.The Eulerian-Lagrangian method is used to obtain detailed cluster characteristics.Because of limits in computing power,no obvious results exist to model particle clusters under high-solids-flux conditions.Because high-solids-flux conditions are used extensively in industrial applications,further experimental and numerical investigations on the clustering behavior in HF/DCFBs are required.

Mesoscale structures and mechanisms in ionic liquids

Ionic liquids(ILs)have attracted intensive attention and have been used widely in many applications because of their diversified properties,which are caused by the special structure of the ILs.Ionic clusters are one of the typical structures that exist widely in the IL system.They are stable under certain conditions and change under other conditions.Ionic clusters are a typical mesoscale phenomenon in mesoscience.In this review,we summarize our recent progress related to ionic clusters,including the ionic-cluster structure,changing mechanisms,and their effect on the physicochemical properties.IL cluster investigation based on mesoscience is very important,will provide new insight into the structures and properties of ILs,and will boost further exploration of IL applications.

Kinematic Structure of a Heavy Rain Event from Dual-Doppler Radar Observations

The detailed kinematic structure of a heavy rain event that occurred in the middle reaches of the Yangtze River was investigated using dual-Doppler radar observation. A variational analysis method was developed to obtain the three-dimensional wind fields. Before the analysis, a data preprocessing procedure was carried out, in which the temporal variation with the scanning time interval and the effect of the earth curvature on the data position were taken into account. The analysis shows that a shear line in the lower and middle levels played an important role in the rainfall event. The precipitation fell mainly on the south end of the shear line where southerly flow prevailed and convergence and updraft were obvious. With the movement and decay of the shear line, the precipitation moved and decayed correspondingly.

Mesoscale regulation of droplet templates to tailor microparticle structures and functions

The hierarchical design of mesoscale structures in droplet templates determines the structure and functionality of the resultant microparticles.In this review,we summarize recent progress on the control of microfluidic emulsion templates for the synthesis of polymeric microparticles with desired functionality and internal structure.We introduce strategies for controlling the morphology and interfacial stability of emulsion templates.These strategies are based on manipulation of the mesoscale structure of amphiphilic molecules and nanoparticles at emulsion-droplet interfaces.We also discuss strategies for controlling the mesoscale structure of microparticles,which involve manipulating the interfacial mass-transfer and chemical reactions during template synthesis.We provide insight on the use of these strategies for the rational design and fabrication of polymeric microparticles with predictable internal structures and functionality at the single-particle level.

NONHYDROSTATIC NUMERICAL SIMULATION FOR THE“96.8”EXTRAORDINARY RAINSTORM AND THE DEVELOPING STRUCTURE OF MESOSCALE SYSTEM

During the period of 3—5 August 1996(for short “96.8”),an extraordinary rainstorm event occurred in Henan,Hebei and Shanxi Provinces in China,resulting in severe flood catastrophe. Synoptic analyses indicated that the stable gross col field and the interaction between a northward moving typhoon(down into low pressure)and its east lateral Pacific subtropical high were the large-and meso-scale circulation conditions of the “96.8” extraordinary rainstorm.The mesoscale typhoon-low and its specific dynamical and thermodynamical structures were directly related to this rainstorm event.The nonhydrostatic version of mesoscale numerical model MM5 was used to conduct investigation of numerical simulation for this case.The simulation with the full physical processes of nonhydrostatic version MM5 was basically possessed of a capability to reproduce the genesis,development and evolution of the large-scale and meso-α scale synoptic systems.The simulative results using a two-way interactive nesting procedure revealed that the typhoon-low was possessed of an intensive coupled mechanism between the dynamical and thermodynamical fields, namely,the developing typhoon-low was possessed of a structure of the.cyclonic vorticity column with warm center and high humidity,the vorticity column on the lower levels was the moist convective instability and negative moist potential vorticity structure:the intensive ascending vertical motion and the intense divergence on upper levels and intensive convergence on the lower levels as well as the development of the convective cloud cluster were intercoupling:the intense southern wind jet companied by the typhoon-low was not only the interaccompanying and intercoupling condition of the development and maintenance of the typhoon-low and convective cloud cluster,but also was the transportable belt of the moisture source and heat energy of the “96.8”extraordinary rainstorm.The analysis of simulative results of precipitation indicated that the distribution of the rainfall belt and rainfall rate was basically consistent with that of the observation in spite of some rainfall centers less or larger than those of the observation for coarse or fine mesh domain,respectively.

Mesomechanics Finite-element Method for Determining the Shear Strength of Mudded Intercalation Materials

A new method regarding mesomechanics finite-element research is proposed to predict the peak shear strength of mudded intercalation materials on a mesoscopic scale. Based on geometric and mechanical parameters, along with the strain failure criteria obtained by sample＇s deformation characteristics, uniaxial compression tests on the sample were simulated through a finite-element model, which yielded values consistent with the data from the laboratory uniaxial compression tests, implying that the method is reasonable. Based on this model, a shear test was performed to calculate the peak shear strength of the mudded intercalation, consistent with values reported in the literature, thereby providing a new approach for investigating the mechanical properties of mudded intercalation materials.

Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

Dual-loop circulating fluidized bed(CFB)reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability.However,the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms,meaning it has been heavily based on empiricism and stepwise experiments.Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them.This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale(EMMS)principle.A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors,to achieve the mass conservation and pressure balance in each circulation loop.Based on the modularization strategy,corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor.This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.

Construction of hierarchical functional nanomaterials for energy conversion and storage

Hierarchical functional nanomaterials have important applications in the fields of new energy and the environment because of performance advantages based on the coupling and collaboration of multilevel structures.The key to application is the design and control of the mesoscale structures,such as the crystal-facet structure,lattice orientation,defects,and dislocations.In this review,we present the controlled synthesis of novel semiconductor oxide and carbon-based nanocomposites with three-dimensional hierarchical structures by the multiphase-reaction process.We describe several typical reaction processes,such as the gas-phase flame-combustion method,the vapor-phase deposition technique,and the solid-liquid interface reaction process,to investigate the properties of fluid flow,mixing,transport,and chemical reaction.We also study the formation mechanism,structural evolution and control methods for hierarchical nanomaterials by using combined experimental and simulation methods.These well-designed and prepared hierarchical functional materials can be used in energy storage and conversion fields.Valuable information is provided for the structural design and performance control of new functional nanocomposites.