Introducing a variable speed of sound in single-component lattice Boltzmann simulations of isothermal fluid flows

To simulate the hydrodynamics and mixing characteristics of chemical reactors by means of a lattice Boltzmann method (LBM), it is essential to consider components with varying molecular weights (and therefore speeds of sound). This option requires modification of the standard equilibrium distribution function and the use of an extended velocity set. In this paper, we show that, for isothermal incompressible single-component non-reactive flows, tuning the speed of sound with a modified equilibrium distribution and an extended velocity set allows for reproducing the proper flow characteristics with strongly reduced errors (compared to LBM simulations on standard lattices). This is done for two isothermal benchmarks, viz. a damped standing pressure wave and a decaying viscous Taylor–Green Vortex. The convergence as a function of the number of lattice nodes used improves substantially for varying values of the speed of sound

Experiments and Modelling of Micro-Jet Assisted Fluidization of Nanopowder

The fluidization of nanoparticle agglomerates can be largely improved by using downward pointing micronozzles, creating a high-velocity jet, as experimentally shown. By discrete particle simulations – treating the agglomerates as single particles – we show that the microjet strongly reduces the amount of gas in voids

Elektrische snoeischaar geeft nauwelijks klachten

Onderzoekers van Wageningen UR hebben onderzocht welke snoeischaar de minste gezondheidsklachten geeft aan hand en arm. Gegevens in bijgaande tabellen: 1) Kenmerken van zeven geteste scharen; 2) Eindoordeel van zeven geteste scharen op spieractiviteit, schokbelasting, ervaren kracht, snoeiprestatie, snoeikwaliteit, handligging en bedienbaarheid, drukpunten en pijn in de hand, geluid, bewegingsvrijheid en ervaren veilighei

Innovaties in de glasgroenteteelt : vergelijking van verschillende methoden voor het laten zakken van tomatenplanten = Innovations in horticulture : comparison of different working methods for lowering of tomato plants

In The Netherlands, the modern way of tomato production involves a high wire system. Here, metal hooks hold a rope that guides the growing tomato plant. Because the plants keep growing during the season, each rope is to be lowered periodically, which requires one-handed lifting. Because each plant weighs 4-6 kg and a complete cycle costs only 1-2 seconds, the task is considered to be strenuous and highly repetitive. Some alternative systems are available or under development, but their eventual load relieving effect is unknown. The present study considered some alternative systems from a theoretical viewpoint and investigated the effects of one particular alternative hook, the Tomguide. This hook eliminates most of the lifting part of the task because of application of a reel on which the rope is winded. The research involved seven experienced persons in six companies. All of the persons performed both tasks, i.e. the standard hook and the Tomguide. Muscular loading, experienced effort and working speed were measured during and after each task. Muscular loading was measured in four shoulder (trapezius and deltoid, left and right side) and two upper arm (biceps, left and right) muscles, applying electromyography (EMG). Static, median and peak load, relative to maximal activation, were calculated. Experienced effort was scored using a 10-point rating scale and a body diagram showing 14 body regions. EMG results showed a significant decrease in peak activity for both upper arm muscles when using the Tomguide. Median activity was reduced only for the right upper arm. If all 6 muscles were pooled, peak activity was reduced significantly, while median activity showed a tendency, without reaching significance. No difference was measured for any of the individual shoulder muscles measured. Experienced effort decreased significantly for the shoulder and upper arm regions, both left and right, in case of the Tomguide. It was observed that the Tomguide task lead to an increase in working time by 27%, compared to the standard hook, possibly partly due to insufficiently functioning of the mechanical brake on the reel. It is concluded that the Tomguide, and probably also comparable reel rope systems, contribute to a reduction of muscular load, in particular of the upper arm muscles, because lifting of the plants is strongly reduced. Because most workers copy their working height for the standard hook into the new situation, attention must be paid to instruction of the proper working height, in order to prevent unnecessarily high load of the shoulder muscles. Besides, final conclusions of the labour demand can only be drawn if the reel system applied is functioning well. The braking system of the Tomguide tested here did not allow for a relaxed working technique

Vergelijking visserij - intensiteit op basis van AIS -VMS in de Voordelta

IMARES voert samen met Deltares en een consortium van 4 partners monitoring uit binnen het project ‘PMR monitoring natuurcompensatie Voordelta’ in opdracht van RWS-WVL. Doel van het project is in kaart te brengen of de compensatiemaatregelen in de Voordelta, als compensatiegebied aangewezen voor de aanleg van de tweede Maasvlakte, daadwerkelijk een (positief) effect hebben op onder andere de bodemfauna. Onderdeel van de compensatiemaatregelen zijn verscherpte regelgeving voor de visserij en gedeeltelijke sluiting voor de visserij