Mesoscale transport phenomena and

Mesoscale Transport Phenomena and Mechanisms in Gas-Liquid Reaction Systems... 

Mesoscale transport phenomena and mechanisms are essential to achieve a more fundamental understanding on the mass, momentum, and heat transfer in the classical... 

Despite these explorations and knowledge on mesoscales, mesoscale transport phenomena and mechanisms would continue to be a chaUenge for multiphase reaction systems. For example, there are currendy no general guidelines to identify the dominant mechanisms and formulate the stability... 

Ning Yang, Mesoscale Transport Phenomena and Mechanisms in Gas-Liquid Reaction Systems Harry E.A. Van den Akker, Mesoscale Flow Structures and Fluid—Particle Interactions... 

Mahoney, J. R., and B. A. Egan. A mesoscale numerical model of atmospheric transport phenomena in urban areas, pp. 1152-1157. In H. M. Englund and W. T. Beery, Eds. Proceedings of the Second International Oean Air Congress. New York Academic Press, 1971. 

The process of formulating mesoscale models from the microscale equations is widely used in transport phenomena (Ferziger Kaper, 1972). For example, heat transfer between the disperse phase and the fluid depends on the Nusselt number, and mass transfer depends on the Sherwood number. Correlations for how the Nusselt and Sherwood numbers depend on the mesoscale variables and the moments of the NDF (e.g. mean particle temperature and mean particle concentration) are available in the literature. As microscale simulations become more and more sophisticated, modified correlations that are based on the microscale results will become more and more common (Beetstra et al, 2007 Holloway et al, 2010 Tenneti et al, 2010). Note that, because the kinetic equation requires mesoscale models that are valid locally in phase space (i.e. for a particular set of mesoscale variables) as opposed to averaged correlations found from macroscale variables, direct numerical simulation of the microscale model is perhaps the only way to obtain the data necessary in order for such models to be thoroughly validated. For example, a macroscale model will depend on the average drag, which is denoted by... 

It is important to construct models that are able to closely mimic the heterogeneity of actual porous media and sufficiently efficient to allow simulation of flow and transport phenomena. To predict the network flow at core scale (for instance, in hydrocarbon reservoirs, packed beds and aquifers), we propose to construct the permeability probability distribution within our model. Our results are shown in Table 2 in this work. Although it is widely understood that the selection of a particular effective permeability probability density will markedly influence simulation results in applications, only a few studies (this paper, among others) describe the manner in which to construct these effective permeability probability density functions from mesoscale information. 

The use of local theories, incorporating parameters such as the eddy viscosity Km and eddy thermal conductivity Ke, has given reasonable descriptions of numerous important flow phenomena, notably large scale atmospheric circulations with small variations in topography and slowly varying surface temperatures. The main reason for this success is that the system dynamics are dominated primarily by inertial effects. In these circumstances it is not necessary that the model precisely describe the role of turbulent momentum and heat transport. By comparison, problems concerned with urban meso-meteorology will be much more sensitive to the assumed mode of the turbulent transport mechanism. The main features of interest for mesoscale calculations involve abrupt... 

In summary, while most studies of atmospheric boundary layer flows have used local theories involving eddy transport coefficients, it is now recognized that turbulent transport coefficients are not strictly a local property of the mean motion but actually depend on the whole flow field and its time history. The importance of this realization in simulating mean properties of atmospheric flows depends on the particular situation. However, for mesoscale phenomena that display abrupt changes in boundary properties, as is often the case in an urban area, local models are not expected to be reliable. 

Each of these scales of atmospheric motion plays a role in air pollution, although over different periods of time. For example, the microscale meteorological effects determine the dispersion of a plume from an industrial stack or a highway over timescales on the order of minutes to a few hours. On the other hand, mesoscale phenomena take place over hours or days and influence the transport and dispersal of pollutants to areas that are hundreds of kilometers from their sources. 

Mesoscale models provide valuable insight into the operation of SOFCs and how the micrometer-scale phenomena translate into the macroscale behavior of the SOFC. By discretely modeling the gas phase and solid phase of the SOFC electrodes, they can investigate the surface reactions and transport in SOFCs, which could lead to advances in the design of the electrodes to improve the electrochemical performance of the SOFC. They are also able to provide macroscale models with effective properties for the transport and reaction parameters based on the local microstracture and physics of the SOFC. 

Molecular simulation techniques can obtain the microscopic information that cannot be detected by current experimental conditions, but the conventional simulation methods stiU have inherent limitations with special mesoscopic scales of various complex forces and complex structure. It is necessary to establish a new mesoscale method that considers the chemical reaction and transport to the larger system at the same time. The roughness and chemical properties of catalyst supporting interface have great influence on chemical and physical adsorption stability of clusters. The problem is that the system is too large for traditional simulation in nano-/micro-/mesoscale. We need a new mesoscale method to study the effect of interface roughness on physical/chemistry phenomena. 

In this chapter, we focus on the core issues of surface/interface structure and interaction under mesoscale based on the phenomena in mesoscale of heterogenous catalysis (mainly on mesoporous Ti02), fluid transportation, wetting, nanofriction, and protein adsorption (Fig. 1). We propose two key factors, which are surface chemical property and surface roughness these two are very critical for material and chemical—biological engineering. To research these objects, we need to combine simulation, AFM measurement, and adsorption experiment methods. 

The new mesoscale method for large systems takes account of chemical reaction, and transport should be estabHshed to examine the reaction mechanism quantitatively and the relationship with the changes of concentration of reactants and products. AFM study shows that the interfacial roughness of catalyst support has a significant impact for clusters on its chemical and physical adsorption stabdity this problem is in the nanometer and micrometer mesoscale traditional simulation also met the problem that studied system is too big to handle. A new medium-scale method is needed to be established to study effects of interfacial roughness on chemical and physical phenomena. 

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