Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

The review deals with drop impacts on thin liquid layers and dry surfaces. The impacts resulting in crown formation are referred to as splashing. Crowns and their propagation are discussed in detail, as well as some additional kindred, albeit nonsplashing, phenomena like drop spreading and deposition, receding (recoil), jetting, fingering, and rebound. The review begins with an explanation of various practical motivations feeding the interest in the fascinating phenomena of drop impact, and the above-mentioned topics are then considered in their experimental, theoretical, and computational aspects.

Drop Impact Dynamics: Splashing, Spreading, Receding, Bouncing ...

Inkjet printing is viewed as a versatile manufacturing tool for applications in materials fabrication in addition to its traditional role in graphics output and marking. The unifying feature in all these applications is the dispensing and precise positioning of very small volumes of fluid (1–100 picoliters) on a substrate before transformation to a solid. The application of inkjet printing to the fabrication of structures for structural or functional materials applications requires an understanding as to how the physical processes that operate during inkjet printing interact with the properties of the fluid precursors used. Here we review the current state of understanding of the mechanisms of drop formation and how this defines the fluid properties that are required for a given liquid to be printable. The interactions between individual drops and the substrate as well as between adjacent drops are important in defining the resolution and accuracy of printed objects. Pattern resolution is limited by the extent to which a liquid drop spreads on a substrate and how spreading changes with the overlap of adjacent drops to form continuous features. There are clearly defined upper and lower bounds to the width of a printed continuous line, which can be defined in terms of materials and process variables. Finer-resolution features can be achieved through appropriate patterning and structuring of the substrate prior to printing, which is essential if polymeric semiconducting devices are to be fabricated. Low advancing and receding contact angles promote printed line stability but are also more prone to solute segregation or “coffee staining” on drying.

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Inkjet Printing of Functional and Structural Materials: Fluid Property Requirements, Feature Stability, and Resolution

Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

/pdf/heat-and-mass-transfer-1yaijfx8vp.pdf

Heat and Mass Transfer

Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

The effect of solid surface thermophysical properties on flow boiling characteristics within microchannels

Influenza dell'effusività sull'atomizzazione secondaria di gocce impattanti su superfici riscaldate

Introduction The flow domain generated by a single drop with diameter D impacting onto a thin liquid film is faced in a variety of industrial applications, including combustion processes, ink-jet printing, pesticide spraying, and others. Therefore, a considerable amount of research has been focused on the morphology and the splashing-deposition limit, mainly, for one-component droplet wall-film interactions, e.g. Cossali et al. [1]. A detailed review that includes experimental, theoretical and numerical aspects of one-component drop impacts can be found in Yarin [2]. However, for twocomponent droplet wall-film interactions the underlying flow mechanisms that lead to deposition or splashing impact morphologies is still a fundamental aspect that is not yet fully understood. Recently, Geppert et al. [3-4] investigated the morphology and the splashing/deposition limit for two-component interactions over a range of Weber numbers (We = ρDv2/σ) and wall-film thicknesses (Η). The results were correlated for the critical We number in the splashing/deposition limit as a function of the normalized wall-film thickness (δ = H/D), in the range of 0.1 < δ < 0.5. In this paper, we additionally show for two-component droplet wall-film interactions that the droplet impact onto very thin liquid films may result in the ejection of secondary droplets, even if no crown-type splashing is observed. These secondary droplets are generated during a crown breakdown starting from the wall-film surface. In Figure 1 this phenomenon is shown for the impact of a hexadecane droplet at We = 840 onto a hyspin wall-film of δ = 0.05. A few moments after drop impingement (τ = tv/D = 3.96), a uniform, smooth and conical crown formation is observed approaching a typical deposition case. However, at τ = 4.75 a crown breakdown can be noticed starting from the liquid

/pdf/two-component-droplet-wall-film-interactions-impact-dynamics-290uuzqv0s.pdf

Marco Marengo

Papers

The effect of solid surface thermophysical properties on flow boiling characteristics within microchannels

Influenza dell'effusività sull'atomizzazione secondaria di gocce impattanti su superfici riscaldate

Two component droplet wall-film interactions: impact dynamics on very thin films

Description, Uncertainty Analysis And Numerical Simulation Of A New Test Rig For Refrigerant Two-Phase Flow Characterisation

Fast response building energy simulation in support to low carbon design and retrofit