D. McGlinchey

Impact-parameter dependence of the nuclear modification of J/ψ production in d+Au collisions at √[sNN]=200 GeV

The centrality dependence of sqrt(s_NN)= 200 GeV d+Au {J/\psi} data, measured in 12 rapidity bins that span -2.2 < y < 2.4, has been fitted using a model containing an effective absorption cross section combined with EPS09 NLO shadowing. The centrality dependence of the shadowing contribution was allowed to vary nonlinearly, employing a variety of assumptions, in an effort to explore the limits of what can be determined from the data. The impact parameter dependencies of the effective absorption cross section and the shadowing parameterization are sufficiently distinct to be determined separately. It is found that the onset of shadowing is a highly nonlinear function of impact parameter. The mid and backward rapidity absorption cross sections are compared with lower energy data and, for times of 0.05 fm/c or greater, data over a broad range of collision energies and rapidities are well described by a model in which the absorption cross section depends only on time spent in the nucleus.

Bend Pressure Drop Predictions Using the Euler-Euler Model in Dense Phase Pneumatic Conveying

Pneumatic conveying of powdered and granular materials is a very common transport technology across a broad range of industries, for example, chemicals, cosmetics, pharmaceuticals, and power generation. As the demands of these industries for greater efficiency increases and to comply with environmental regulations there is a need for a more fundamental understanding of the behavior of materials in pneumatic conveying systems. The approach presented in this article is to develop a model of a section of pneumatic conveying line, a horizontal or vertical 90° bend, in the commercial CFD software package FLUENT and to describe the multiphase flow behavior by the mixture or Eulerian method. Models of this type have been used in the past to show qualitative and quantitative agreement between model and experiment. The model results presented were compared with experimental data gathered from an industrial-scale pneumatic conveying test system. Broad qualitative agreement in trends and flow patterns were found. Quantitative comparisons were less uniform, with predictions from around 10% to 90% different from experimental results, depending on conveying conditions and bend orientation.

An experimental technique for the analysis of slug flows in pneumatic pipelines using pressure measurements

An experimental technique has been developed to measure the flow characteristics of slugs in dense phase pneumatic conveying using pressure measurements. This method is based on the unique characteristics of slug flows in pipes, i.e., an axial pressure fluctuation along the pipeline and a pressure difference in the radial direction at the back of a slug. Standard differential pressure transducers were used in this study and the influence of the finite response time of these transducers was considered. Experiments were conducted over a range of gas-solids flow conditions and experimental data were analyzed to describe the behavior of solids slugs through pipes. The calculated slug velocity and length using axial pressure measurements were confirmed by video recordings, and the synthesis between axial and radial pressure signals showed reasonable agreement in flow pattern analysis. This relatively simple measuring technique has been found effective in detecting solids slugs traveling through horizontal pipes and will distinguish various flow regimes. It provides a useful and easily applied tool for system optimizing and benchmarking in industrial applications.

The Vibratory Unconfined Compression Tester(VUCT) for Cohesive Solids

A Vibrational Unconfined Compression Tester has been developed which superimposes applied vibration upon axial compression for a cylindrical sample of cohesive material. The VUCT has been applied to systems of wet sands. During applied vibration, the material retreated into elastic space within each vibration cycle. The top cap stress/axial strain curve progressed through a series of hysteresis loops. The instantaneous values of peak axial stress, Pi, and averaged values, Pave, have been compared with peak stresses for control tests with no applied vibration, Pnv. Pave always gave lower values than Pi, due to the cyclic nature of the system. However, in some tests Pi was not significantly different from Pnv. Thus, Pave is not an appropriate parameter for determination of the effects of vibration upon material strength. In some cases, vibration caused a genuine reduction in material strength as measured by peak stress. This depended upon applied vibration and material properties. The maximum reduction in strength did not correspond to resonance frequency.

Analysis and Measurements from a Prototype In-Line Thermal Solids Mass Flowmeter in an Industrial Scale Dilute Phase Pneumatic Conveying System

The in-line measurement of solids mass flow rate in a prototype industrial scale pneumatic conveying pipeline by a thermal method has been investigated over a range of dilute conveying conditions. A thermal method of determining solids mass flow rate should, in principle, be capable of achieving a reliable measurement regardless of; inhomogeneities in solids’ distribution, irregularities in velocity profile and variations in particle size or shape. The instrument described in this article operates by the injection of heat energy into the pipeline by way of a heated section and measuring the resultant change in solids’ temperature using infrared sensors. Initial results from the thermal instrument are compared with measurements from a gain in weight system showing good correlation. The importance of sensor window condition and temperature on measurement is discussed.

Axial and Radial Pressure Drops of Dense Phase Plugs

ABSTRACT An experimental technique to measure various characteristics of plug flow in dense phase pneumatic conveying systems based on the unique characteristics of plug flow, i.e., the fluctuation of axial pressure drop along a pipeline and pressure difference in the radial direction at the back of a plug, was developed by Li et al. (2002). Based on this work, a further experimental study combined with numerical modeling was carried out to describe the structure of plugs through the analysis of the measurements of pressure difference in both axial and radial directions. A theoretical explanation of these pressure differences was proposed and agrees very well with the recorded signals of pressure difference from differential transducers. This explanation will prove useful in understanding plug structures in industrial applications.

Breakage functions of particles of four different materials subjected to uniaxial compression

ABSTRACT Particle breakage is a common problem in the conveying and handling of particulate solids. The phenomenon of particle breakage has been studied by experiments by a number of researchers in order to describe the process of breakage by mathematical functions. The development of comminution functions that can suitably describe the breakage behavior of granular materials can lead to a significant improvement in the design and efficiency of particulate solids handling equipment. The present study focuses on developing the strength distribution and the breakage functions of particles of four different materials subjected to uniaxial compressive loading. Single particles were compressed until fracture in order to determine their strength distribution and the fragments were investigated to determine their size distribution. The parameters of logistic function and breakage function were obtained by curve-fitting of the functions to the strength distribution and size distribution of the fragments, respectively. These functions were then implemented in the BGU-DEM code which was used to carry out discrete element method (DEM) simulations on single particle breakage by compression. The simulations produced a similar mass distribution of fragments to the breakage function obtained from the experimental data.

Sampling and Characterization of Bulk Particulate Materials and Products

This chapter is aimed primarily at engineers working in industry with little formal training or education in particle technology or bulk solids and aims to provide an overview of simple sampling and characterisation methods and techniques many of which can be undertaken with standard laboratory apparatus. It is written in a fairly informal style, however, reference is made to the academic literature where appropriate. A descriptive distinction between random sampling and systematic sampling is given, followed by advice on sampling methods covering a range of sampling techniques. Once a sample has been obtained, typically, either the properties of individual particles or of the bulk are required. An overview of common characterisation techniques, apparatus and interpretation of results is given. This is by necessity a non-exhaustive review and a list of references and standards is provided for the interested reader.

Can Scalable Design of Wings for Flapping Wing Micro Air Vehicle Be Inspired by Natural Flyers

Lift production is constantly a great challenge for flapping wing micro air vehicles (MAVs). Designing a workable wing, therefore, plays an essential role. Dimensional analysis is an effective and valuable tool in studying the biomechanics of flyers. In this paper, geometric similarity study is firstly presented. Then, the ratio is defined and employed in wing performance estimation before the lumped parameter is induced and utilized in wing design. Comprehensive scaling laws on relation of wing performances for natural flyers are next investigated and developed via statistical analysis before being utilized to examine the wing design. Through geometric similarity study and statistical analysis, the results show that the aspect ratio and lumped parameter are independent on mass, and the lumped parameter is inversely proportional to the aspect ratio. The lumped parameters and aspect ratio of flapping wing MAVs correspond to the range of wing performances of natural flyers. Also, the wing performances of existing flapping wing MAVs are examined and follow the scaling laws. Last, the manufactured wings of the flapping wing MAVs are summarized. Our results will, therefore, provide a simple but powerful guideline for biologists and engineers who study the morphology of natural flyers and design flapping wing MAVs.

A computational intelligence based dislocation recognition during molecular dynamics simulation

Dislocation evolution in metal is the majority response of external stress or strain during the deformation. In this paper, a computational intelligence aided dislocation recognition algorithm which is integrated in a molecular dynamics simulation is proposed. This algorithm is inspired by genetic algorithm(GA) and follows the main GA process in which the initial population is the disperse nodes set and is under the select, crossover to evolve the new generation of nodes set. Finally, two examples of the dislocation recognition during fatigue simulation by using this algorithm is provided with good result when comparing with the traditional MD post process method.