Three dimensional numerical modelling of full-scale hydraulic structures

This study presents the three-dimensional (3D) hydraulic modelling of free surface flows over complex full-scale hydraulic structures. The work outlined therein forms part of a larger ongoing project which focuses on the assessment of the capabilities of different 3D computational fluid dynamics (CFD) techniques to reproduce hydraulic flows over real scale spillway structures and on the comparison with physical scale models. The aim of the first part of the study, presented in this work, is to evaluate a range of 3D free surface methods with a particular focus on the Eulerian mesh-based Volume of Fluid (VOF) technique. A range of 2D and 3D free surface approaches are initially investigated and validated using an experimental case with a simple geometry. The commercial solver Ansys Fluent and the CFD open source platform OpenFOAM are used to implement the VOF model and the DualSPHysics code is used to conduct simulations using the Lagrangian meshless particle-based Smoothed Particle Hydrodynamics (SPH) method. The hydraulic flow over a real hydraulic structure is subsequently modelled, applying the evaluated model implementations. The scheme consists of a newly constructed flood storage reservoir with a labyrinth weir and extended spillway. Different hydraulic conditions is modelled using a 1:25 physical scale hydraulic model of the prototype which is used to validate the numerical models. In order to remove numerical model uncertainties and provide insight into scale effects, numerical simulations are applied first to the physical scale hydraulic model and then to the full-scale prototype. Results show the model is capable of accurately predicting the interface features as well as the velocity and water depths measured in the physical model. It is observed that full-scale predictions present approximately a 17% increase in velocity and a 20% decrease in water depth compared to the equivalent scaled predictions

Environmental Health Indicators: A review of initiatives worldwide

Purpose – The extent to which research into the design and development of environmental health indicators (EHIs) has translated into operational programmes is unclear. The purpose of this paper is to identify EHI initiatives worldwide, distil the EHIs and draw lessons from the experience. Design/methodology/approach – A systematic internet-based review was undertaken. Programmes were selected for inclusion if they: first, had the ability to monitor both the physical environment and associated health outcomes; and second, the parent agency had the ability to influence policies related to the environment and health. Findings – The small number of eligible programmes indicates EHI initiatives are not yet well established, especially in developing countries. The use of indicators was also limited by uncertainties in the exposure-response relationships that they implied, and the consequent inability to translate the indicators into a common measure of health impact. In addition, there is no information on the extent to which the indicators have been applied in decision making, nor on the policy implications of using indicators. Practical implications – More effort is needed to encourage the development and use of more balanced and informative sets of indicators, and to evaluate their use and outcomes in terms of health benefits. Originality/value – The time is right for a substantial review paper on EHIs as they are now being used by a number of organisations and to the knowledge this is the first review of operational EHI programmes worldwide

A Cognitively-Oriented Approach to Task Analysis and Test Development

Clear descriptions of job expertise are required to support applications and improvements in personnel training and job performance. This report describes a practical approach to task analysis that integrates the issues, content, and methods of cognitive science and personnel psychology. Cognitively oriented task analysis employs a breadth, then depth, strategy for identifying job expertise. Starting with a task-by-knowledge framework, job expertise is successively elaborated using interviews, expert ratings, and protocol analyses. The application of task analysis results to the development of written performance measures is described to illustrate the contributions of this approach to measurement validity. Task analysis results show that much of what has been missing in using existing task analysis methods is the mental aspects of performance related to interactions among task dimensions, task characteristics, and contexts. Two appendixes provide an example of knowledge elicitation and representation and item writing guidelines for performance measures

Multiwavelength observations of the blazar BL Lacertae: a new fast TeV γ-ray flare

Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan (South Korea). Published in Proceeding of Science.Observations of fast TeV γ-ray flares from blazars reveal the extreme compactness of emitting regions in blazar jets. Combined with very-long-baseline radio interferometry measurements, they probe the structure and emission mechanism of the jet. We report on a fast TeV γ-ray flare from BL Lacertae observed by VERITAS, with a rise time of about 2.3 hours and a decay time of about 36 minutes. The peak flux at >200 GeV measured with the 4-minute binned light curve is (4.2±0.6)×10−6photonsm−2s−1, or ∼180% the Crab Nebula flux. Variability in GeV γ-ray, X-ray, and optical flux, as well as in optical and radio polarization was observed around the time of the TeV γ-ray flare. A possible superluminal knot was identified in the VLBA observations at 43 GHz. The flare constrains the size of the emitting region, and is consistent with several theoretical models with stationary shocks

Transition phenomena in unstably stratified turbulent flows

We study experimentally and theoretically transition phenomena caused by the external forcing from Rayleigh-Benard convection with the large-scale circulation (LSC) to the limiting regime of unstably stratified turbulent flow without LSC whereby the temperature field behaves like a passive scalar. In the experiments we use the Rayleigh-B\'enard apparatus with an additional source of turbulence produced by two oscillating grids located nearby the side walls of the chamber. When the frequency of the grid oscillations is larger than 2 Hz, the large-scale circulation (LSC) in turbulent convection is destroyed, and the destruction of the LSC is accompanied by a strong change of the mean temperature distribution. However, in all regimes of the unstably stratified turbulent flow the ratio $\big[(\ell_x \nabla_x T)^2 + (\ell_y \nabla_y T)^2 + (\ell_z \nabla_z T)^2\big] /$ varies slightly (even in the range of parameters whereby the behaviour of the temperature field is different from that of the passive scalar). Here $\ell_i$ are the integral scales of turbulence along x, y, z directions, T and \theta are the mean and fluctuating parts of the fluid temperature. At all frequencies of the grid oscillations we have detected the long-term nonlinear oscillations of the mean temperature. The theoretical predictions based on the budget equations for turbulent kinetic energy, turbulent temperature fluctuations and turbulent heat flux, are in agreement with the experimental results.Comment: 14 pages, 14 figures, REVTEX4-1, revised versio

Investigating scale effects of a hydraulic physical model with 3D CFD

In the present study, the three-dimensional (3D) Computational Fluid Dynamics (CFD) Volume of Fluid (VOF) method is validated to reproduce hydraulic free surface flows over a labyrinth weir and a spillway for several flow rates using the open source toolbox OpenFOAM 3.0.1 and the commercial CFD package ANSYS Fluent 17.2. The CFD solvers are employed to simulate the 1:25 scale Froude number similarity physical model of the scheme, with validation conducted using experimental observations and measurements. It is found that both solvers are capable of accurately reproducing the velocities and depths measured in the physical model and are also able to capture complex flow features. The models are applied to simulate the prototype hydraulic flows so that scale effects from the physical model can be quantified. Results show the overall decrease in water depth and increase in velocity in the prototype can be up to 15% and 10%, respectively, for the lower flow rates, with scale effects reducing for larger flow rates. The prototype scale simulations also exhibit some variation in the labyrinth weir rating curve when compared to the scaled case; showing lower heads upstream of the crest for the same discharge. As theory would suggest, discrepancies in the rating curve at the two scales are more pronounced for low flow rates

Correlation effects during liquid infiltration into hydrophobic nanoporous mediums

Correlation effects arising during liquid infiltration into hydrophobic porous medium are considered. On the basis of these effects a mechanism of energy absorption at filling porous medium by nonwetting liquid is suggested. In accordance with this mechanism, the absorption of mechanical energy is a result expenditure of energy for the formation of menisci in the pores on the shell of the infinite cluster and expenditure of energy for the formation of liquid-porous medium interface in the pores belonging to the infinite cluster of filled pores. It was found that in dependences on the porosity and, consequently, in dependences on the number of filled pores neighbors, the thermal effect of filling can be either positive or negative and the cycle of infiltration-defiltration can be closed with full outflow of liquid. It can occur under certain relation between percolation properties of porous medium and the energy characteristics of the liquid-porous medium interface and the liquid-gas interface. It is shown that a consecutive account of these correlation effects and percolation properties of the pores space during infiltration allow to describe all experimental data under discussion

Contact orderability up to conjugation

We study in this paper the remnants of the contact partial order on the orbits of the adjoint action of contactomorphism groups on their Lie algebras. Our main interest is a class of non-compact contact manifolds, called convex at infinity.Comment: 28 pages, 1 figur

Reverberation Mapping Results for Five Seyfert 1 Galaxies

We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as a part of a recent reverberation mapping program. The data were collected at several observatories over a 140-day span beginning in 2010 August and ending in 2011 January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501, 3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between variations in the 5100 Angstrom continuum and the H-beta broad emission line. We then used these measurements to calculate the mass of the supermassive black hole at the center of each of these galaxies. Our new measurements substantially improve previous measurements of MBH and the size of the broad line-emitting region for four sources and add a measurement for one new object. Our new measurements are consistent with photoionization physics regulating the location of the broad line region in active galactic nuclei.Comment: 45 pages, 5 figures. Accepted for publication in ApJ. For a brief video explaining the key results of this paper, see http://www.youtube.com/user/OSUAstronom