bluuebunny/crossref_metadata_2025 huggingface dataset:
Super-light concrete with pearl-chains
Authors: Hertz K.D.
Published: October 2009

The paper presents a new technology invented by the author by means of which it is possible to create very light concrete structures. The new super-light structures are resource-saving in terms of consumption of raw materials and energy for production and transport, and the cost is often less than half that of similar structures in concrete and steel. They are heat-insulating, fire-resistant and they open up the possibility for large spans and the creation of advanced shapes. Fields of application include roofs, shells, beams, columns, walls, façades, offshore structures, tunnels and structures with large spans for bridges, factories, warehouses, shopping centres, car parks, assembly and sports halls and so on. The new structures are new applications for well-understood components, so it is not necessary to prove that they are possible. However, the paper presents tests that were made to illustrate the applicability and to reveal any potential hidden problems. Continuing research will aim to reduce the weight and thereby the resource consumption further. In addition, the paper introduces pearl-chain reinforcement, which is a new principle for creating compression and tension zones. A small number of simple mass-produced prefabricated components are used to establish compression and tension zones for optimised or advanced shapes in super-light structures. Furthermore, the principle provides new options for prestressing light aggregate concrete structures in general. Pearl-chain reinforcement is self-supporting. It is visible and open for inspection before being cast into a structure, and it can support moulds for the structure, reducing the need for scaffolding. Stable meshes of pearl-chain reinforcement are advantageous for both large-scale structures, such as bridges, girders, shells and domes, and for small-scale applications, such as façade elements, crash barriers and secondary structures. One special small-scale application of the principle is in frame building, where super-light frames with pearl-chain-reinforced components have some of the same advantages as timber-frame structures with regard to stability, heat insulation, economy and simple erection processes, but without the disadvantages of fire and rot.
Seismic study of a typical radial floodgate in a UK gravity dam
Authors: Daniell W. E. , Taylor C. A.
Published: October 2009

A seismic evaluation of a typical UK radial gate design, based on the arrangement at Kilmorack Dam, was conducted for Scottish and Southern Energy. Its purpose was to assess the general seismic risk to radial gates in the UK, and to evaluate appropriate methods for their seismic analysis. The study included dynamic hammer tests on the gate, the seismic analysis of a three-dimensional finite element model, and the equivalent-static analysis of simple two-dimensional models. Natural frequencies and mode shapes from the tests correlated reasonably with the three-dimensional model, validating it for seismic analysis. A response analysis was run for the three-dimensional model using artificial accelerograms generated from a standard UK earthquake response spectrum. The demand on the gate for the seismic condition was almost double the hydrostatic demand, indicating that this and other similar non-seismically designed gates may be vulnerable to earthquakes. Generally, the equivalent-static analysis yielded higher responses than the dynamic three-dimensional analysis, but the two-dimensional models could not represent important three-dimensional effects in the gate. This study showed that the equivalent-static analysis of simple models is appropriate for preliminary seismic assessments of radial gates, while dynamic analyses of three-dimensional models should be employed for detailed analyses.
Laboratory calibration of open channel bed resistance
Authors: Marriott M. J. , Day R. A.
Published: October 2009

This paper deals with the calibration of bed resistance to flow in a straight open channel contained within a laboratory flume. The longitudinal slope of the flume was able to be varied, and so the flow could be subcritical or supercritical. The flow was in the transitional turbulent region, with Reynolds numbers in the range 3 × 104 to 2 × 105. The calibration demonstrates experimentally a prediction linking the value of Manning's n with longitudinal slope in this region, and indicates a useful approach to define this relationship. This is of benefit for laboratory work in the smooth or transitional turbulent region, particularly if it is wished to employ Manning's formula because of its extensive use in river engineering practice.
A new approach for directing proactive sewer maintenance
Authors: Fenner R. A. , Sweeting L. , Marriott M. J.
Published: October 2009

Maintenance and asset management of the UK sewerage network is based on a policy of selective rehabilitation of critical sewers which represent about 20% of most drainage systems. Continuing failures on an ageing network, together with customer and regulator pressure, have increased the need for water companies to become more proactive in the maintenance of non-critical sewers, which form the remaining 80% of the nation's sewerage assets. This paper describes a flexible methodology for directing proactive sewer maintenance in the light of a changing perception of how urban drainage systems should be managed. Until recently, non-critical (or category C) sewers received only reactive maintenance. What is now required is an effective means of directing maintenance resources so as to target those parts of the network in greatest need of attention. Management strategies can no longer focus on a preselected subset of assets but should identify the correct subset for each catchment for which maintenance activity will be most effective. Cost constraints prohibit the widespread collection of new data regarding the condition of all sewers, so the approach described here is based on the analysis of existing historical sewer event data and asset information. Appropriate forms of data analysis, within the constraints of current levels of data availability, have been evaluated, and a two-stage decision support model for sewer maintenance is proposed. This uses geographical information system (GIS) software to rank variable-sized grid squares into priority zones for action. A detailed analysis of each pipe length within those grid squares most at risk from sewer failure is then performed using a simple Bayesian statistical model. To demonstrate the approach the procedures are applied to a real catchment as part of a case study, and based on a wider analysis of data from several catchments observations are made concerning the factors most commonly associated with serviceability failures in sewers.
Simulation of channel confluence and bifurcation using the CCHE2D model
Authors: Khan A. A. , Cadavid R. , Wang S. S.-Y.
Published: October 2009

The CCHE2D model, a depth-averaged, two-dimensional, unsteady-flow model, developed at the National Center for Computational Hydroscience and Engineering, has been verified for channel confluence and bifurcation applications. The computational efficiency for natural-river applications was the governing factor in the selection of the mixing-length model for turbulence closure. In the absence of field data, flume data for channel bifurcation and confluence collected in the laboratory were used to verify the simulated results. The simulated depth-averaged velocity and water surface profiles in the main and branch channels of a bifurcating channel compare well with the experimental data. In addition, the ratio of the discharge in the branch channel to the upstream discharge in the main channel, which is the most commonly sought value in the case of bifurcation, is in good agreement with the experimental data. The width and length of the recirculation zone in the branch channel are satisfactorily predicted by the model. The simulation results for the water surface profile near a channel confluence agree well with the measured data.
Risk-based benefit assessment of coastal cliff protection
Authors: Hall J. W. , Lee E. M. , Meadowcroft I. C.
Published: October 2009

Cliff protection schemes are designed to reduce the risk of damage or permanent loss of cliff-top assets as a result of coastal cliff recession and landsliding. To identify the most efficient scheme in economic terms requires an assessment of the beneficial risk reduction that each of the scheme options will achieve. This paper introduces a risk-based approach to evaluating the economic benefits of coastal cliff protection. The approach is applicable to economic appraisal of schemes for currently protected and unprotected coastal sites. Example appraisals of sites prone to progressive cliff recession, large catastrophic landslides and minor recurrent ground movement are included. Methods for including and structuring expert judgements of failure probabilities are explored. A risk-based approach is preferable to current practice, which is essentially deterministic, because it reflects the uncertainty that is inherent in recession predictions. Current deterministic methods can underestimate the economic risk associated with cliff recession.
Geometrical and roughness effects on compound channel resistance
Authors: Myers W. R. C. , Lyness J. F. , Cassells J. B. , O'Sullivan J. J.
Published: October 2009

This paper presents an analysis of resistance coefficients derived from measurements taken in phases A, B and C of the research programme of the UK Flood Channel Facility (FCF). The FCF is a large-scale compound channel facility and the programme has included straight and meandering planforms, smooth and mobile main channel roughnesses and smooth and rod-roughened floodplain boundaries. Floodplain roughness consisted of 25 mm surface-penetrating dowel rods. Data were also obtained for straight trapezoidal channels for comparison by confining flow to the main channels. Stage–discharge relationships were derived which enabled calculation of Manning's roughness coefficient values for a range of selected relative depths for each geometry, planform and roughness case. Graphs are presented of the variation with depth of Manning's coefficient for each geometry and roughness expressed as a ratio of smooth straight compound, or straight trapezoidal channel data. These presentations quantify the increase or decrease of roughness coefficient resulting form cross-sectional geometry, planform and boundary roughness. It is suggested that this represents a possible valid approach to the estimation of Manning's roughness coefficient in compound channels and rivers.
Graphical solution to the problem of sequent depth and energy loss in spatial hydraulic jump
Authors: Agarwal V. C.
Published: October 2009

A graphical solution in the form of design charts and monograph is given for the computation of sequent depth and energy loss in the spatial hydraulic jump formed in gradually and abruptly expanding channels. These are intended to be of practical help to design engineers.
Wave speed–discharge relationship from cross-section survey
Authors: Tang X. , Knight D. W. , Samuels P. G.
Published: October 2009

This paper tackles a practical problem in flood routing, the estimation of the speed of propagation of the flood wave. It is well known that this propagation speed varies with the discharge in quite a complex manner for natural rivers. The principal innovative step in this paper is the identification of a relatively simple conceptual model of river geometry to obtain two methods for generating realistic wave speeds from a standard river cross-section survey. These are verified against data from two rivers in the UK, showing good agreement with wave speeds deduced from long-term flow records. This work is expected to be of particular value in building forecasting models of ungauged or partially gauged river systems, as it removes the need for long concurrent records to estimate wave speeds.
Comparison of river training measures in the Rhine—catchment and their effects on flood behaviour
Authors: Belz J. U. , Busch N. , Engel H. , Gasber G.
Published: October 2009

For more than 25 years the Federal Institute of Hydrology has been investigating the impact of large-scale river training of waterways on flood behaviour by means of mathematical modelling and evaluations of gauge station recordings. At the rivers and river reaches of the Upper Rhine, Moselle and Saar, river training had considerable effects, which must be analysed individually according to the distinctive character of works carried out. At the Moselle and the upper Rhine the changes in flood behaviour can be proved by respective measuring results. The purpose of this article is to work out the coherence between cause and effect of these changes more clearly.
Standard specifications for flow measurement structures
Authors: White W. R.
Published: October 2009

The performance data given in existing standards for open channel flow measurement structures are qualified by strict limitations derived from the original supporting research. This research did not anticipate the more extensive range of conditions used today. Commonly used measurement structures often operate outside the limits specified in the current standards and this can lead to gross inaccuracies in measured flows. This paper describes an investigation carried out to extend the range of conditions where the performance of particular structures can be predicted, thereby permitting the extension of the scope of certain flow measurement standards. Current flow measurement standards were scrutinised and the key limitations were identified. Additionally, a review of the current usage of flow measurement structures was undertaken based on registers of measurement structures, reports and papers on studies undertaken, asset surveys and the views of individual experts. This information was then drawn together in order to determine what laboratory tests might be undertaken to provide data which would enable the standard specifications to be extended. Following this review, the research programme was formulated to cover three of the more important issues identified namely: to extend the range of permissible flow conditions in terms of head to weir height ratios; to evaluate the performance characteristics of compound weirs without divide piers; and to extend the availability of drowned flow performance data.
A TVD MacCormack scheme for transcritical flow
Authors: Mingham C. G. , Causon D. M. , Ingram D. M.
Published: October 2009

A simple update to a well-known classical scheme for solving the non-linear shallow water equations is described which is computationally efficient and able to resolve accurately both subcritical and supercritical flows. The solver is the MacCormack scheme with a total variation diminishing term appended to the corrector step which eliminates spurious numerical oscillations which often arise when the convective terms are discretized using classical central difference schemes. The scheme is explicit, second-order in space and time and formulated in finite volume form for ease of implementation on a general boundary conforming grid. Bench mark solutions in one and two dimensions involving both steady and non-steady flows are shown to illustrate the high spatial accuracy and computational efficiency of the method compared to the MacCormack schemes and a modern Riemann-based upwind scheme.
Discharge prediction in straight mobile bed compound channels
Authors: Cassells J. B. C. , Lambert M. F. , Myers R. W. C.
Published: October 2009

Most of the recent advances in techniques to predict the discharge capacity of compound channels have been based on experimental results from fixed bed laboratory models. This paper represents a significant departure from this trend by introducing a mobile bed in the main channel. As a result, sediment will be transported and reshaped by the flow in the main channel and this will lead to an increase in roughness as bedforms are created. The introduction of a mobile bed provides another degree of freedom and increases the complexity of the experiments. The discharge prediction problem still remains and methods for predicting the channel discharge capacity are examined. Experimental results from the United Kingdom Flood Channel Facility (UK FCF) and from the University of Ulster show that an improved estimate of both the zonal and overall discharge can be estimated using the Weighted Divided Channel method. Percentage errors for each discharge assessment were averaged for each data set; the most accurate method was the WDCM with an average error of 2·4 and the least accurate was the Divided Channel Method with vertical divisions with an over prediction in discharge of 16·0%. Results from tests on the rare situation of a compound channel with smooth floodplains and a rough main channel indicated that the usual explanation given for the effects of the momentum interaction between these two regions may need further investigation.
Eastbourne coast protection, 1991–2000
Authors: Waters B. E.
Published: October 2009

Following a series of storms in the late 1980s and in December 1991, Eastbourne's beaches were subjected to significant drawdown from which they failed to recover. Such was the cost and frequency of carrying out storm damage repairs and keeping up with the scale of destruction, that the coast protection authority, Eastbourne Borough Council, appointed Posford Duvivier to carry out investigations into the existing coast protection measures and to report on a strategy for their future management. This paper details the ensuing reports, site investigations, mathematical and physical modelling which led up to the design and construction of the chosen remedial measures.
Effects of bed degradation on riprap protection at bridge piers
Authors: Lauchlan C. S. , Melville B. W.
Published: October 2009

Scouring around bridge piers results from a combination of local, general and contraction scour mechanisms. To counteract local scouring of sediment, armouring countermeasures such as riprap are commonly used. The riprap protects the bed from erosional forces close to the pier. General and contraction scour result in degradation of the whole channel bed. This study aims to assess the impact of this degradation on riprap layers installed to prevent local scouring. Experiments, conducted in a laboratory flume, were used to identify changes to riprap stability and failure mechanisms caused by a steady reduction in the sediment bed level. Both a uniform and a non-uniform bed material were tested. It was observed that degradation of the sediment bed allowed the riprap layer to be undermined and riprap stones to subside into the sediment bed. After substantial degradation of the channel bed the riprap stone layer disintegrates and the stones no longer protect the pier from local scour.
Empirical travel time estimation in a distribution network
Authors: Skipworth P. J. , Machell J. , Saul A. J.
Published: October 2009

In the calibration procedure adopted for most hydraulic network models, parameters are adjusted to ensure that measured and computed pressures are approximately equal. Little emphasis is placed on confirmation of a correct flowrate distribution. Such procedures can therefore promote erroneous flowrate solutions. However, it is becoming increasingly common for network models to have water quality modelling capabilities. The age of water, and many chemical reactions associated with changes in water quality are largely dependent on residence time, which is a function of the flowrate distribution. The need for greater accuracy in flowrate prediction has highlighted the need to enhance the standard calibration and verification procedure. An automated and easily repeated procedure for the empirical estimation of travel-time is described. The method involved increasing the conductivity of a pocket of water entering the network via the addition of a tracer solution, and tracking its progress using conductivity loggers. Results of the application of this method in a distribution network are compared with age of water predictions from network water quality modelling software. Discrepancies were attributable to the inaccuracy of a model calibrated using pressure alone. Large discrepancies between modelled and measured age of water existed where the flow regime was complex.
Woolston New Weir and River Mersey Diversion
Authors: Tonks D. M. , Howells R. , Bettess R. , Morris M. W.
Published: October 2009

The Woolston Weir and River Mersey Diversion project involved provision of a new hydraulic control structure, diversion channel and ancillary works on the River Mersey, near Warrington, for the Manchester Ship Canal Company. The weir is a substantial structure, nearly 80 m wide. It includes the largest low-head, air-regulated siphon weir to date in the UK, with nine bays, each 4 m width, plus 17·8 m wide ‘ogee’-type weirs either side, and a fishpass. Design involved extensive physical and numerical modelling. The weir was built in dewatered open cut in difficult ground, within a new channel some 600 m length cutting across an ancient loop in the Mersey. The scheme has provided an economic means of closely controlling a wide range of flows, for flood and navigation purposes, consistent with a pleasant river environment.
Cardiff Bay Barrage: planning and design
Authors: Hunter P. D. , Gander H. C. W.
Published: October 2009

In 1986 Mr Peter Walker, Secretary of State for Wales, accepted the view that the Cardiff Bay area was in urgent need of urban renewal. The government, with support from the Vale of Glamorgan, the county of South Glamorgan and the City of Cardiff, created the Cardiff Bay Development Corporation (CBDC). Its remit was to regenerate some 1100 ha in this area of south Cardiff. The keystone to this strategy was the construction of the Cardiff Bay Barrage, to impound the estuaries of the rivers Taff and Ely, creating a 200 ha fresh water lake and about 12 km of attractive waterfront. Works of this magnitude and scope on tidal waters at that time required an Act of Parliament. The 1100 m long barrage includes sluices, locks, an outer harbour, fish pass, embankment and bridges. The sluices have a capacity of 2300 m3/s, to discharge combined flood flows from the Taff and Ely. The gates close to exclude the highest tides, allowing bay water levels to be controlled even in extreme conditions. A large fish pass allows migratory fish to move easily between the rivers and the sea. The paper describes the overall objectives of the Cardiff Bay Barrage, and the design of the barrage.
Hydromechanical equipment for Cardiff Bay Barrage
Authors: Pope N. J.
Published: October 2009

The barrage now constructed across the entrance to Cardiff Bay is acting as the catalyst in facilitating the revitalisation of the old industrial and port areas of the capital city of Wales. The fresh water bay created by the barrage is designed to stimulate development opportunities around the water's edge and to provide extensive leisure opportunities. Fresh water flowing from the Taff and Ely rivers is retained on the upstream side of the barrage while salt water from the seaward side is prevented from entering the bay when the tide is higher than the bay level by automatically closing the gates. The main contract for the barrage works was awarded to a main contractor (Balfour Beatty-Costain Joint Venture) in May 1994 and was effectively completed in late 2000. A contract for all of the hydromechanical works was sublet to a specialist German water control gate designer and manufacturer (Noell Gmbh), with a separate contract let for all of the electrical works (Lintott), including power distribution around the site and water control gate operation. This paper describes the various elements of hydromechanical equipment employed on the barrage to provide passage for water, vessels, fish, and road and pedestrian traffic on or through the barrage.
Far-field impact of water injection dredging in the Crouch River
Authors: Winterwerp J. C. , Wang Z. B. , van Kester J. A. Th. M. , Verweij J. F.
Published: October 2009

Water injection dredging (WID) is a dredging technique by which the sediment to be removed is fluidised through low-pressure injection of water into the bed. Upon fluidisation, the mud flows as a density current away from the dredging site. In this paper the far-field effects of WID are evaluated—that is, the large-scale dispersion and deposition patterns of the mobilised sediments are determined. This is done with numerical simulations using a two-layered fluid mud model, which takes account of the effects of supercritical fluid mud flow, and for all mud exchange processes in the vertical direction. This model is applied to simulate a dredging work carried out in the River Crouch, UK. The agreement of the numerical results with observed patterns of dispersion and deposition is satisfactory. Next it is shown how this model can be used to evaluate alternative dredging strategies. With respect to the WID operations in the River Crouch, it is concluded that the far-field effects of the work are small.
Grassed drainage channels—hydraullic resistance characteristic
Authors: Escarameia M. , Gasowski Y. , May R.
Published: October 2009

Current methods of estimating the hydraulic resistance of grass were developed for the relatively high water depths found in rivers and large channels, and for cultivars not common in the UK. This paper describes work carried out to determine the hydraulic resistance of grass-lined drainage channels, with particular emphasis on shallow channels used for road drainage. Grass types that are common in the UK, which have slow growth rates and are tolerant to salt and wet conditions, were identified as suitable for drainage channels. Experimental work with natural grass led to the development of resistance formulae where the Manning's n coefficient is dependent on the grass height and on the product of the velocity and hydraulic radius. Issues related to the construction and maintenance of grassed channels are also discussed in the paper.
Evaluation and visualisation of risk to water resources
Authors: McIntyre N. , Lees M. , Wheater H. , Onof C. , Connorton B.
Published: October 2009

A traditional difficulty encountered in water resource planning is the inherent uncertainty in demand and supply capability. Over recent years this uncertainty has increased for the UK water industry, owing for example to forecasts of climate change and impending directives from Europe, and in the face of such uncertainty it is no longer justifiable to design water resource systems in a deterministic fashion. Design objectives should be risk-based, and it is likely that both investors and regulators will soon request formal risk evaluation prior to major investment or strategic decisions. Consequently, there is a need for probabilistic, or risk-based, approaches to water resource assessment. A methodology for evaluation and visualisation of risk to security of water resources is presented, based on hydrological frequency of occurrence and uncertainty-based analysis of headroom (that is, the difference between supply capability and demand). The methodology makes it possible to calculate and visualise the probability of system failure for particular hydrological conditions or the probability of system failure in an arbitrary year, and to make preventive planning or operational decisions. The proposed approach is illustrated with a case study.
Coupled seismic response analysis of rubble-mound breakwaters
Authors: Memos C. D. , Kiara A. , Pavlidis E.
Published: October 2009

The present investigation considers the seismic behaviour of rubble-mound breakwaters by taking into account the coupling between the hydrodynamic loading and the shaking of the mound. To this end a boundary element code was developed that predicts the hydrodynamic pressures on the faces of the breakwater. This was coupled with a geotechnical code providing the accelerations along the height of the structure. Shaking-table experiments were carried out to verify the model. The methodology was then applied to real-life structures. It is found that the quality of the foundation soil directly and decisively affects the pressures and induced accelerations. Weak foundations can trigger large structure deformations. In tall structures the pressures and accelerations of the mound increase with frequency. Far from resonance, the maximum pressures on the slopes occur at 40% of the water depth from the bed. The total hydrodynamic force can be high under resonance conditions. It is also found that Westergaard's expression overestimates pressures, except in cases of rigid base and shakings of small acceleration and high frequency. The coupling of the hydrodynamic loading and the shaking of the mound, as well as the frequency dependence of the model, represent advances over the conventional Westergaard's relation.
Protection of bridge piers using a sacrificial sill
Authors: Chiew Y. , Lim S.
Published: October 2009

This experimental study explores the effectiveness of using a sacrificial sill as a pier scour countermeasure. Experiments were conducted under both clear-water and live-bed conditions. Many interdependent parameters affecting the sill performance were systematically examined. The results show that the sill is efficient in reducing the equilibrium clear-water scour depth, reaching a maximum percentage reduction of pier scour depth, %RDP, of approximately 50% under the most favourable condition. The optimum state occurs under the following conditions: (a) the sill is vertical; (b) the sill height is larger than 0·3 times the depth of flow; (c) the clear distance between the pier and sill is 4·4 times the pier width; and (d) the angle of attack is zero. A large angle of attack or flow skewness is detrimental to the performance of the sill. However, this shortcoming may be overcome by installing a sill with a wedge angle of 270°. The efficiency of the sill decreases under live-bed conditions, with the %RDP reducing to approximately 20% at a velocity ratio, U/Uc = 2·6.
A note on uniform open channel flow in circular pipes
Authors: Rajaratnam N. , Ead S. A.
Published: October 2009

This paper presents a brief analysis of uniform open channel flow in circular pipes and introduces a dimensionless discharge parameter Q*. When the pipe just flows full, Q* becomes Q*f which varies inversely with a modified Manning's n written as n*. This relationship has been checked with experimental observations.
Defining a network of benchmark catchments for the UK
Authors: Bradford R. B. , Marsh T. J.
Published: October 2009

A network of benchmark catchments has been selected to improve the ability to identify and interpret hydrological trends throughout the UK. The designation of this network is examined within the context of a wider review of the gauging station network designed to address a broad range of strategic hydrological needs.
Application and validation of numerical codes in the prediction of compound channel flows
Authors: Wilson C. A. M. E. , Stoesser T. , Olsen N. R. B. , Bates P. D.
Published: October 2009

This paper attempts to compare the accuracy of a two-dimensional (2D) depth-averaged code (TELEMAC-2D) and a three-dimensional (3D) code (SSIIM) in the numerical simulation of free surface flows. Assessment was conducted using benchmark data collected from a meandering compound channel at the UK EPSRC Flood Channel Facility. For both codes a standard k–ε turbulence model was employed to simulate the flow field. Assessment of both codes was based on the prediction of depth-averaged velocity traverses around a meander bend, flow features inferred by velocity vectors in the horizontal plane, and water surface elevations for both low and high relative flow depths. In addition, predictions with the 3D code of velocities parallel and perpendicular to the main channel direction are compared with those observed in the experimental programme. Both codes predict the lateral distribution of depth-averaged velocity in the main channel with reasonable accuracy at low relative flow depth, with the 3D code predicting better than the 2D code (maximum percentage errors in depth-averaged velocity are 16% and 22% respectively). At a higher flow depth no extra accuracy in the prediction of depth-averaged velocity is to be gained from the 3D model than from the 2D model, although the 3D model can predict the correct location and direction of secondary currents. For all flow conditions better accuracy was achieved for both codes at the apex section where the mean flow direction is more aligned with the local main channel direction. An accuracy of within 20% can be expected for predictions of depth-averaged velocity magnitude from a 3D model using a standard isotropic representation of turbulence.
An engineering approach to wave propagation
Authors: Iglesias G. , Negro V.
Published: October 2009

Wave propagation is a major topic in most coastal engineering projects. In this paper a new system of equations governing wave propagation is proposed along with a numerical model to solve them. The main intention throughout their derivation was to set the basis for a new engineering tool. Thanks to the ray–front coordinate system, the equations lend themselves to a convenient numerical treatment, which has resulted in practical advantages with respect to parabolic models—the most widespread in coastal engineering practice. Their major limitation is overcome while keeping the computational cost low, as the model proposed in this work allows unrestricted variation of the propagation direction. The problems associated with ray intersections or caustics in conventional ray models are not encountered, as both refraction and diffraction (rather than solely refraction) are considered. After validation through comparison with analytical solutions and physical models, the model utility has been proven by solving engineering cases to which a parabolic model would not be applicable.
Dredging on the Lower Danube in Romania
Authors: van Drimmelen N. J.
Published: October 2009

The river Danube is the second longest river in Europe, with a total length of some 2680 km and a catchment area of 817 000 km2. The source of the river lies in the Black Forest in Germany, at the confluence of two smaller streams, the Brigach and the Breg, in Donaueschingen. Navigation is possible between Kelheim in Germany and Sulina in Romania, where the Danube flows into the Black Sea. In Romania, the Danube is 1075 km long, the last 175 km of which (as far as the city of Braila) is navigable for seagoing vessels. This stretch is called the Maritime or Lower Danube (in Romanian: Dunarea de Jos). The seaports of the Lower Danube lying within Romanian territory are Braila, Galati, Tulcea and Sulina. The ports of Reni, Izmail and Kilija are in the Ukraine. Near the city of Tulcea the Danube splits into three branches, known as Kilia, Sulina and Saint Georges. For navigation purposes the Sulina branch or, as it is called today, the Sulina Canal, forms the vital link between the Danube seaports and the Black Sea. The permissible draught of vessels on the Lower Danube is 24 ft (7·32 m). Vessels with a length of 225 m and a breadth of 36 m have found their way to sea after construction at shipyards on the Lower Danube.
Air entrainment and oxygen transfer in a venturi
Authors: Baylar A. , Emiroglu M. E.
Published: October 2009

The dissolved oxygen content is a prime indicator of the quality of water. Water jets can increase dissolved oxygen levels when the jet impact velocity exceeds a critical velocity. In this paper, air entrainment rate and oxygen transfer efficiency of a venturi device with air holes at the throat portion were studied experimentally, and in particular the effect of varying numbers, positions, and the open/closed status of the air holes. A negative pressure drew air in through holes at the throat portion of the venturi device. The resulting aeration of the jet affected its expansion, its shape, the air entrainment rate, the bubble penetration depth, and hence the oxygen transfer efficiency. It was demonstrated that the values of the air entrainment rate and the oxygen transfer efficiency of the venturi device were significantly higher than those for a circular nozzle.
Study of aeration efficiency at stepped channels
Authors: Baylar A. , Emiroglu M. E.
Published: October 2009

The oxygen concentration in surface waters is a prime indicator of the quality of that water for human use as well as use by the aquatic biota. Hydraulic structures can increase dissolved oxygen levels by creating turbulent conditions where small air bubbles are carried into the bulk of the flow. Stepped channels are a particular instance of this, and the aeration efficiency of such structures has not been studied in the laboratory or the field. This paper studies stepped channels having different length/height ratios and step heights and their effects on the aeration performance. A regression equation predicting the aeration efficiency was developed for stepped channels. The results demonstrated that L/h and step height had a significant effect on the aeration efficiency of stepped channels. Aeration efficiency generally increased with increasing step height and with decreasing L/h.
Chichester emergency flood alleviation project, winter 2000/2001
Authors: Hoad R. S. , Gilham A. M. , Fawcett D. S.
Published: October 2009

The River Lavant is a small ephemeral chalk stream, which is culverted through the city of Chichester. In 1994 widespread flooding resulted when the capacity of the culverts was exceeded and the river overtopped its bank. Subsequently a local multi-agency Strategic Coordinating Group was formed, and a permanent flood alleviation scheme was developed through the planning process. In November 2000, after a period of very heavy rain, the River Lavant again threatened flooding. A large-scale pumping operation to divert some water around the city was brought into place by the Fire Brigade. Additional alleviation capacity was urgently needed, and local design resources were committed to adapt the permanent scheme for rapid implementation. The project comprised several major pumping operations and open channels over 5 km long with a choked diversion to protect the village of Merston. The A27 trunk road and the railway embankment carrying the mainline along the south coast lie across the route. Piped crossings were designed involving liaison with Railtrack and the Highways Agency. Documents for the whole scheme were put together while funding approval was sought. Despite the emergency conditions, both archaeological and ecological studies were undertaken, particularly for water vole, bat and badger habitats. On 4 December 2000 construction commenced in three packages costing a total of £1·3 million, with a programme to complete all but the main rail crossing before Christmas. However, further bad weather intervened, and the partially completed works were brought into use carrying floodwater less than two weeks later. In the New Year the rail crossing was constructed during a weekend possession. The paper focuses on the implementation of the project, including emergency response, multi-agency cooperation, team working, fast-tracking approvals, unique technical solutions, and rapid construction while ensuring compatibility with the full scheme.
Computer modelling of two-stage meandering channel flows
Authors: Rameshwaran P. , Shiono K.
Published: October 2009

Prediction of flow in two-stage meandering channels for overbank flow was undertaken using a commercially available computer model. The software, TELEMAC-2D, solves the depth-averaged Navier–Stokes equations with non-structured grids for free surface flow. The model results are compared with the experimental data obtained from the UK Flood Channel Facility. Advection schemes offered in TELEMAC-2D are examined for their influence upon a bed friction coefficient. The effect of mesh resolution on solution accuracy is also investigated. The simulated distributions of depth-averaged velocity and boundary shear stress are also used to investigate the accuracy of the TELEMAC-2D prediction by comparison with the experimental data. The 1D and local Manning coefficients calculated using the experimental data are compared with the calibrated Manning coefficient. The results show that the choice of Manning coefficient is vital for an accurate prediction of overbank flow in two-stage meandering channels, and that transverse turbulence diffusion is not so significant.
Clinical Application of Ischemic Preconditioning in the Elderly
Authors: Abete Pasquale , Cacciatore Francesco , Testa Gianluca , Della-Morte David , Galizia Gianluigi , Ferrara Nicola , Rengo Franco
Published: October 2009

A mild stress such as brief ischemic episodes may protect the heart from a successive and more prolonged myocardial ischemia (ischemic preconditioning). This phenomenon is considered a typical “hormetic mechanism” by which the heart is immunized from pathological insults such as myocardial ischemia. This mechanism is reduced with aging and it may be restored and/or preserved by drugs such as adenosine or nicorandil, a mitochondrial KATP channels, and lifestyle interventions such as physical activity and/or hypocaloric diet. Moreover, since the mechanisms involved in cardiac ischemic preconditioning have been established basic and clinical investigators are encouraged to test several drug in well-controlled animal and human studies in order to prevent and/or restore the age-related reduction of ischemic preconditioning.
Evolutionary Theory and Studies of Model Organisms Predict a Cautiously Positive Perspective on the Therapeutic Use of Hormesis for Healthy Aging in Humans
Authors: S⊘rensen Jesper G. , Holmstrup Martin , Sarup Pernille , Loeschcke Volker
Published: October 2009

Hormesis, the beneficial effects of mild stress exposures, is a well documented phenomenon in a range of organisms. The documentation mainly relies on relatively simple and controlled laboratory investigations. In order to better understand hormesis and predict the outcome of more complex and realistic conditions, a number of key issues should be investigated in much more detail. One obstacle is the development of precise treatments optimized for single individuals. Only then can we progress with the use of hormesis as a therapeutic tool for humans.
It is Time to Thoroughly Study the Effects of Mild Stress in Rodents, but also in Human Beings
Authors: Le Bourg Éric
Published: October 2009

Many experiments on the effect of mild stress on aging have been done in invertebrates, but not in mammals. Using mild stress to improve healthspan seems to be possible, because the few studies on humans which have been published appear to be promising. Particularly, one may wonder whether heat shocks could be of some use in therapy or as an integrated part of daily life of elderly people. However, the top priority is probably to study more thoroughly the effects of mild stress in rodents, and not only in invertebrates.
The Europeanisation of Educational Leadership: Much Ado about Nothing?
Authors: Clarke Simon , Wildy Helen
Published: October 2009

This introductory article examines the elusive concept of Europeanisation and discusses the implications of this process for educational leadership, especially as it applies to the formation of school leaders. With an eye to Europeanisation, the article also investigates four pertinent themes extrapolated from the scholarly discussion contained in this special issue of the European Educational Research Journal that may be relevant to the broader context of European educational leadership. These themes are: European understandings of the nature and purpose of educational leadership; the practice of educational leadership in the contemporary European policy environment; the preparation, development and support of school leaders according to a European coordinated approach; and the veracity of a Europeanised educational leadership.
Analytic wave functions and energies for two-dimensional $$
\mathcal{P}\mathcal{T}
$$-symmetric quartic potentials
Authors: Tichý Vladimír , Skála Lubomír
Published: October 2009

Analytic wave functions and the corresponding energies for a class of the $$
\mathcal{P}\mathcal{T}
$$-symmetric two-dimensional quartic potentials are found. The general form of the solutions is discussed.
Dielectric properties of Ba3Sr2DyTi3V7O30 ceramics
Authors: Sahoo Priyadarshini , Panigrahi Anuradha , Patri Sunanda , Choudhary Rasm
Published: October 2009

A polycrystalline sample, Ba3Sr2DyTi3V7O30, with tungsten bronze structure was prepared by a mixed-oxide method at high temperature (950°C). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound was studied by scanning electron microscopy. The dielectric anomaly at 321°C may be attributed to the ferro-paraelectric phase transitions. This was also confirmed from the appearance of a hysteresis loop. The nature of variation of the ac conductivity and value of activation energy at different temperature regions, suggest that the conduction process is of mixed-type (i.e., ionic-polaronic and space charge generated from the oxygen ion vacancies).
Magnetism, entropy, and the first nano-machines
Authors: Mitra-Delmotte Gargi , Mitra Asoke
Published: October 2009

The efficiency of bio-molecular motors stems from reversible interactions ∼ k
B
T; weak bonds stabilizing intermediate states (enabling direct conversion of chemical into mechanical energy). For their (unknown) origins, we suggest that a magnetically structured phase (MSP) formed via accretion of superparamagnetic particles (S-PPs) during serpentinization (including magnetite formation) of igneous rocks comprising the Hadean Ocean floor, had hosted motor-like diffusion of ligand-bound S-PPs through its ‘template’-layers. Ramifications range from optical activity to quantum coherence. A gentle flux gradient offers both detailed-balance breaking non-equilibrium and asymmetry to a magnetic dipole, undergoing infinitesimal spin-alignment changes. Periodic perturbation of this background by local H-fields of templatepartners can lead to periodic high and low-template affinity states, due to the dipole’s magnetic degree of freedom. An accompanying magnetocaloric effect allows interchange between system-entropy and bath temperature. We speculate on a magnetic reproducer in a setting close to the submarine hydrothermal mound-scenario of Russell and coworkers that could evolve bio-ratchets.
Transportation of megawatt millijoule laser pulses via optical fibers?
Authors: Tauer Johannes , Kofler Heinrich , Schwarz Elisabeth , Wintner Ernst
Published: October 2009

Laser ignition is considered to be one of the most promising future concepts for internal combustion engines. It combines the legally required reduction of pollutant emissions and higher engine efficiencies. The igniting plasma is generated by a focused pulsed laser beam. Having pulse durations of a few nanoseconds, the pulse energy E
p for reliable ignition amounts to the order of 10 mJ. Different methods of laser ignition with an emphasis on fiber-based systems will be discussed and evaluated.