Aquatic suction feeding dynamics: insights from computational modelling

Aquatic suction feeding in vertebrates involves extremely unsteady flow, externally as well as internally of the expanding mouth cavity. Consequently, studying the hydrodynamics involved in this process is a challenging research area, where experimental studies and mathematical models gradually aid our understanding of how suction feeding works mechanically. Especially for flow patterns inside the mouth cavity, our current knowledge is almost entirely based on modelling studies. In the present paper, we critically discuss some of the assumptions and limitations of previous analytical models of suction feeding using computational fluid dynamics.     

Call For Paper The 9th International Workshop on Ship and Marine Hydrodynamics（IWSH＇2015, 26- 28 August 2015, Glasgow,UK）

<正>In 1999,the first International Workshop on Ship Hydrodynamics was successfully held in Wuhan,China.Then it was held in Wuhan,Shanghai,Zhenjiang,Harbin,Seoul in subsequent every two years.These Conferences had drawn a variety of international delegates including scientists,engineers and researchers with a common interest in ship hydrodynamics.They provided a forum to promote scientific advancement,technological progress,information exchange,and cooperation among engineers and researchers in ship and ocean engineering and other related fields.The coming IWSH’2015 conference will change its full name to International Workshop on Ship and Marine Hydrodynamics.It will be hosted and organized by University of Strathclyde,UK and sponsored by Lloyd’s Register,UK.The IWSH’2015 will be a platform for engineers and researchers to keep abreast     

三角形网格在水动力水环境数学模型中的应用

综合介绍了三角形网格在水动力、水环境数学模型中的若干实用技术。     

防渗渠道顶托渗漏量计算方法的理论探讨

针对灌区高地下水位条件,探讨在饱和渗流水顶托条件下,采取防渗衬砌措施前后渠道渗漏量的理论计算方法,分析研究现有解析计算经典公式的特点及其适应性.根据水力学和水动力学原理,推出理论上可行、结构合理和简便适用的解析计算方法,并用数值模拟计算进行了验证,结果表明,本文解析法与数值法的计算结果比较接近.     

Solid Suspension in Jet Mixers

Experiments have been carried out with jet mixers to study the solid suspension characteristics. The jet velocities required for solid suspension in 0.5 and 1 m ID tanks were measured experimentally. The nozzle diameter was varied from 0.0156 to 0.05 m. The nozzle clearance from the tank bottom was varied from 0.1 to 0.9 m. Tap water and sand of average sizes 100, 300, and 500 µm were used. The solid loading was varied from 1 to 5% (wt.). The effect of nozzle angle was also studied. A semi‐empirical model has been developed to predict the jet velocity needed to achieve a certain degree of suspension.     

Hydrodynamics of the Stripper Section of Fluid Cokers

The hydrodynamics of fluid bed cokers were studied by analyzing pressure fluctuations and particle motion in a half‐column cold model, geometrically and dynamically similar (with key dimensionless groups matched) to the stripper section of two commercial fluid cokers. Superficial gas velocity and solids circulation strongly affected the hydrodynamics. The pressure drop over the top section of the stripper decreased at high solids circulation fluxes and high gas velocities due to flooding. Flooding occurred prematurely when fouling was simulated. Steam redistribution did not improve stripper performance for the conditions investigated. However, steep sheds on the top row, aeration behind the solids exit and standpipe aeration all improved solids circulation, leading to reduced fouling in two commercial fluid cokers.     

ON THE FORMATION OF THE BULGE IN A SPILLING BREAKING WATER WAVE

The early stages of a spilling breaking water wave leading to the formation of a bulge on the forward face of the wave are investigated. In this study, simultaneous space-time measurements of the free-surface elevation of a spilling breaking water wave are recorded and analyzed. The analysis, carried out in the frame of reference moving with the crest of the wave,reveals that the formation of the bulge is due to the presence of a shock-like mode. In the previous frame of reference, the shock itself is unsteady but its (spatial) location is time independent and coincides with the "toe" of the bulge. As time increases, the shock undergoes a flip (a reflection symmetry) with respect to the midpoint of our time interval. Such a flip is responsible for an abrupt increase of the wave steepe-ness, which will lead to wave breaking at later times. Following these observations, we present a two-dimensional quantitative model which reproduces both the formation of the bulge and the sudden increase of the wave stee     

Integrated process simulation of primary shaping: multi scale approaches

We investigate simulation approaches for the modelling of the primary shaping processes micro powder injection moulding and micro casting. We could reproduce the segregation during micro powder injection moulding (MicroPIM) with a simulation using particle methods. The phase field method allows for accurate prediction of the dynamics of solidification of a melt, whereby model order reduction is used to limit the computational effort. The results give valuable advice for the process conduct and the dimensioning of the micro parts.     

Multiphase Reactor Database Interrogation and Computing at the Finger Tip

A learning approach is proposed to critically evaluate the hydrodynamic, heat and mass transfer parameters for multiphase reactors. Packaged as interactive software, this learning approach exposes students, engineers and researchers to a range of reactor features. It allows gaining insights in computing reactor characteristics, sifting through databases, choosing the fittest correlations, embedding proprietary models and databanks for critical analysis. The software developed at Laval University integrates comprehensive databanks and correlations on gas-liquid co- and counter-current packed beds.     

Testing and numerical simulation of a medium strength rock material under unconfined compression loading

This study aims to numerically and experimentally investigate the response of a medium strength rock material under unconfined compression loading up to failure. The unconfined compressive strength (UCS) is one of the most important parameters in characterising rock material behaviour. Hence the UCS is crucial in understanding the failure mechanism of fractured rocks. An effective approach to determine the UCS and to investigate the behaviours of rock materials under unconfined compression is essential in the majority of research fields of rock mechanics. The experimental configuration for the unconfined compression test, suggested by the protocols of the ASTM standard, has some limitations which affect the accuracy in determination of the real UCS. Among several alternative configurations proposed, the Mogi's configuration seems to be the most appropriate one. Therefore, the ASTM and Mogi's configurations were used to perform the tests on a medium strength rock material, i.e. Pietra Serena sandstone. The results using two configurations were discussed in terms of the differences. The tests were also replicated in LS-DYNA using a finite element method (FEM) coupled smooth particle hydrodynamics (SPH) technique. This technique is employed in this study due to its capabilities to cope with large deformation issues related to the rocks. An advanced material model, called the Karagozian and Case Concrete (KCC) model, is implemented in the numerical simulations. The KCC model consists of three independent fixed failure surfaces and it can consider the damage accumulation based on the current state of stress among these failure surfaces. An equation-of-state (EOS) is used in conjunction with KCC material model for decoupling the volumetric and deviatoric responses. The numerical and experimental results were finally compared with the focus on the stress–strain diagram and the failure patterns. The comparison shows that the numerical results are in good agreement with the experimental results.