Free-surface channel flow around a square cylinder

The free-surface channel flow around a square cylinder is analysed, over a wide range of blocking ratios, using three-dimensional simulations. The state of the flow is characterised in terms of the Froude number upstream and downstream of the square cylinder. The simulations confirm the presence of the subcritical and choked states, and provide new insight into the supercritical state and band-gap through an analysis of how the momentum flux varies with Froude number along the channel. The influence of the blocking ratio on the flow state and drag force is analysed and shows the significant rise of drag in the choked regime

Theoretical and Experimental Activity on Ejector Refrigeration

Abstract Ejector refrigeration has been studied at DIEF (Dipartimento di Ingegneria Industriale Firenze) since the '90s. Use of environmentally safe fluids (steam) was addressed. A two-stage prototype with cooling capacity 5 kW was optimized and built. Later, the CRMC prescription for the design of the supersonic diffuser was focused. By a gradual reduction of the fluid velocity and a continuous profile, the CRMC design promises a reduction of the normal shock that usually develops in the mixing chamber. A second 40 kWf prototype was designed in 2010 for an industrial partner (Frigel Firenze s.p.a.). The design procedure used a thermodynamic code accounting for real gas behavior. This code gives a first design of the mixing chamber and diffuser according to the CRMC criterion. It also gives an estimation of the friction loss along the diffuser. A comparison between different operating fluids was performed and resulted in the selection of R245fa. A first design of the ejector was manufactured in carbon fiber. The primary nozzle is mounted on a movable support, in order to change its axial position with respect to the mixing chamber. In terms of COP, first results were below the values predicted by the simulation code. Meanwhile a numerical simulation was in progress with FLUENT. From the first CFD results it was decided that the diffuser throat had to be moved forward from the primary nozzle exit, in order to allow a complete mixing between the primary and secondary flows, and enlarged, the losses encountered in the mixing process being higher than expected and hence the fluid density lower. This produced a second ejector design, which was manufactured and tested in 2012, showing improved performance. These results suggested a third design, with a further lengthened diffuser, which has undergone a complete testing campaign, allowing validation of the CFD results. The activity performed till now suggests that ejector refrigeration plants have a robust operation and can be easily manufactured at relatively low cost with off-the-shelf components, a part from the ejector itself, which however represents a small fraction of the system cost. However, the COP is lower with respect to absorption refrigeration and hence needs substantial improvement through detailed thermodynamic and CFD design optimization

Tsunami fragility curves of a RC structure through different analytical methods

Recent tsunami events have stimulated research activity into tsunami fragility functions which have been largely based on empirical data. However, empirical fragility functions are biased because the influence of earthquake and tsunami damage are difficult to separate. We develop a new theoretical framework to assess the structural performance of a building due to tsunami inundation by drawing on recent experimental and theoretical progress at UCL on building. Different nonlinear static analyses, i.e. constant-height pushover (CHPO) and variable-height pushover (VHPO), are compared with nonlinear dynamic analysis in assessing the fragility curves of a case study structure for a set of realistic tsunami wave traces. The results of VHPO provide a good prediction of collapse fragility curves obtained from the dynamic analysis under a wide range of tsunami time-histories. On the other hand, CHPO provides a larger, i.e. about 10% in median value, fragility in case global failure is considered and a smaller fragility for local shear failure. On the basis of these results, it is recommended that VHPO be used in future fragility analysis of buildings subjected to tsunami

Strawberries

This is the Strawberries chapter in Cornell Guide to Growing Fruit at Home. It features information and instruction for the home fruit grower.Choosing cultivars, buying plants, site selection, growing methods, planting and early care, managing your planting, diseases and pests, day-neutral strawberries, harvest.Garden-Based Learning, Department of Horticulture, Cornell University

More Minor Fruits

This is the More Minor Fruits chapter in Cornell Guide to Growing Fruit at Home. It features information and instruction for the home fruit grower.Choosing cultivars, propagation, site selection, planting, trellising, persimmons, pawpaws, mulberries, juneberries, highbush cranberries, Cornelian cherries, beach plums, buffaloberries, quinces, fertilization, harvest.Garden-Based Learning, Department of Horticulture, Cornell University

Tree Fruits

This is the Tree Fruit chapter in Cornell Guide to Growing Fruit at Home. It features information and instruction for the home tree fruit grower.Choosing cultivars, rootstocks, nursery stock, planting, managing grass and weeds, fertilizing, pruning and training basics, training and pruning young apple and pear trees, pruning bearing apple and pear trees, rejuvenating old apple and pear trees, pruning and training cherry and plum trees, pruning and training peaches, thinning fruit, diseases and insects, harvest.Garden-Based Learning, Department of Horticulture, Cornell University

Hardy Kiwifruit

This is the Hardy Kiwifruit chapter in Cornell Guide to Growing Fruit at Home. It features information and instruction for the home fruit grower.Choosing cultivars, propagation, site selection and soil preparation, planting, trellising, pruning and mulching, fertilization, harvest.Garden-Based Learning, Department of Horticulture, Cornell University

Grapes

This is the Grape chapter in Cornell Guide to Growing Fruit at Home. It features information and instruction for the home grape grower.Choosing cultivars, purchasing or propagating vines, site selection, planting and early care, fertilizing, pruning and training young vines, pruning mature vines, pruning neglected vines, training vines to an arbor, diseases and insects, harvest, seedless table grapes.Garden-Based Learning, Department of Horticulture, Cornell University

A comparative study of open and closed heat-engines for small-scale CHP applications

In this paper the authors compare and contrast open and closed-cycle heat engines. First of all, by way of example and to aid discussion, the performance of proprietary externally heated closed-cycle Stirling engines is compared with that of internally heated open Otto cycle engines. Both types of engine have disadvantages and merits and this suggested that in order to accommodate the best of both engine types an externally-heated open-cycle engine might offer a more satisfactory solution for small-scale combined heat and power (CHP) systems. To investigate this possibility further the paper goes on to compare the performance of externally-heated and recuperated Joule hot-air cycle engines with that of an externally-heated closed Stirling cycle engines. The results show that an externally heated recuperated open Joule cycle engine can exceed that of a closed cycle Stirling engine operating between the same heat source and sink temperatures when a variable temperature heat source is used