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Urban winds can cause a risk to pedestrian safety if not properly assessed. High-rise buildings produce a complex flow field at ground level, where regions of accelerated and recirculating flows are present. Gust wind speeds provide an indication of the maximal speed pedestrian might experience due to the unsteady flow. In this study, low- and high-fidelity numerical and experimental techniques to predict pedestrian level winds are tested on a realistic full-scale test-route at the University of Birmingham Campus during a storm event. Results show that it is beneficial to increase the complexity of simulations as a direct correspondence exists between the gust wind speed and the turbulent environment. While not much gain is achieved switching from Irwin Probes to hot-wire anemometry, LES greatly outperforms RANS and challenges experimental simulations in terms of reliability. The validity of the peak factor is also questioned and a general comment on the adequacy of each technique is discussed.

This paper considers a process through which the wind costs the agricultural industry hundreds of millions of pounds per year - crop lodging. Lodging is the displacement of crops by wind (and rain) that can result in either stem breakage or uprooting. In particular this paper builds upon recent work to develop a generalised model of the lodging process and presents the results of several experimental campaigns to identify dynamic and aerodynamic parameters that are required as inputs to the model in order to estimate lodging wind speeds. These experiments were carried out at various sites in the UK and the Republic of Ireland to determine the natural frequencies, damping ratios and drag areas of maize, oats and oil seed rape. The experimental methodology, which was based upon the tracking of plant displacements, was shown to be robust, and consistent values of the parameters were obtained, albeit with much larger experimental uncertainties than would normally be expected in wind engineering applications. The values of these parameters were also consistent with those of earlier measurements for wheat. The generalised model was then used to determine lodging wind speeds for the three crops, and an assessment was made of the effect of experimental uncertainties in dynamic, aerodynamic and agronomic variables on the predicted values. In broad terms the generalised lodging model was shown to well describe the crop behaviour for isolated crops, and it was shown that it could be used in a simplified form for interlocked crop canopies. It was also shown that uncertainties in the aerodynamic parameters resulted in uncertainties of around an order of magnitude in lodging risk, whilst typical variations between plants in some crop parameters (notably stem strength and radius) could result in lodging risk uncertainties of two orders of magnitude.

We present a chat bot interface for the Coq proof assistant system. The bot provides a new modality of interaction with Coq that functions across multiple devices and platforms. Our system is particularly suitable for mobile platforms, Android and iOS. The basic architecture of the bot software is reviewed as are the outcomes of several rounds of beta-testing. Potential implications of the system are discussed, such as the possibility of a seamless collaborative proof environment.

Correlated noise is studied in the context of distributed sensing problems. Previous work has examined the problem of performing distributed estimation in the presence of sensor defects. These defects disrupt sensor measurements but allow the other subsystems of the sensor node to operate normally. Provably optimal and fully distributed estimation algorithms exist for this scenario. A series of computer simulation experiments was conducted to measure how these estimation algorithms are affected by the presence of correlations between various random quantities in the problem setup. Numerical results demonstrate that, in particular network configurations, correlations between sensor defects and communication links can practically alter the performance of distributed estimation algorithms.

Relative crosswinds when coupled with transient aerodynamic effects associated with freight trains can have large velocity magnitudes, potentially affecting the stability of not only the train but also containers loaded onto the train. This paper describes a series of moving model crosswind experiments conducted at the University of Birmingham's TRAIN rig facility using a Class 66 hauled container freight train fitted with an on-board surface pressure monitoring system. In the paper the term 'freight train' refers to a series of flatbed wagons loaded with ISO standard shipping containers hauled by a Class 66 locomotive. By altering the container loading efficiency it was possible to develop an understanding of influencing factors on forces subjected to a loaded container. Surface pressure coefficient data has been recorded at a yaw angle of 30°; and were compared with data corresponding to a typical passenger train. In general, similar magnitudes of pressure coefficients have been observed. However, areas associated with large flow separation exhibited greater magnitudes than previously observed. The pressure coefficient magnitudes measured on the container surface exhibited clear dependence on container loading configuration. A series of pressure gradients were observed for different container faces, relating to the crosswind flow over the container and a series of vortices formed at unshielded container edges. It was possible to calculate the overall mean aerodynamic load coefficients as a discrete integral of forces acting on each pressure tap area. Larger magnitudes for aerodynamic load coefficients were observed as container loading efficiency was reduced and the space size in front of the measuring container increased. Overall the results from this paper offer for the first time a definitive study on the influence of container loading configuration on the characteristics of aerodynamic loads subjected to a container freight train travelling through a crosswind.

For the first time, an extensive numerical study of the effect of crosswinds on the flow around a cyclist on a bicycle with stationary wheels has been undertaken for crosswind (yaw) angles ranging from 0° to 90°. The flow field and the aerodynamic forces have been obtained using three numerical techniques: Reynolds Averaged Navier Stokes (RANS), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES). RANS simulations have been undertaken for all the range of yaw angles to provide a general insight of the flow around a cyclist, whilst DES and LES have been undertaken at 15° yaw angle in order to investigate the time-varying flow physics in detail. The aerodynamic forces have been compared with a series of wind tunnel experiments. The RANS results showed the development of large flow separation around the bicycle with increasing yaw angles. The instantaneous flow structures and the auto-spectral densities of the time histories of the force coefficients are identified and revealed that the DES and LES turbulence models are able to predict the dominant frequencies found in the physical experiments. This work provides an improved understanding of the flow characteristics around a cyclist in crosswinds that will hopefully help to improve the safety of cyclists.

Transient winds, such as thunderstorm downbursts, are the cause of design-load wind speeds in manycountries. An understanding of the loading experienced by buildings during a downburst is thereforeimportant to allow well designed and engineered buildings to be constructed. In contrast to boundarylayer winds, the maximum wind speed in thunderstorm downbursts occurs as low as z m ¼30 m abovethe ground, within the range of heights of man-made structures, suggesting that the wind loading will bedependent on the building eaves height relative to z m . In a novel set of experiments, the University ofBirmingham Transient Wind Simulator (a 1 m diameter impinging jet with aperture control) has beenused to simulate a downburst striking buildings of different heights, ranging from below to above z m .Two forms of building have been used – a square-plan, flat-roofed structure, and a rectangular, portal-frame – at three angles (0°,45° and 90°) relative to the radial wind direction. Pressure coefficients havebeen calculated (using eaves height velocity) over the roofs of these buildings, and are shown to be ofgreatest magnitude when the roof is above the region of maximum outflow velocity, with the exceptionof windward edges perpendicular to the flow, when they are generally greatest for the lowest buildingheights.& 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license(http://creativecommons.org/licenses/by/4.0/).

To reduce air resistance, time trial cyclists and triathletes lower their torso angle. The aim of this study was to investigate the effect of lowering time trial torso angle positions on muscle activation patterns and crank torque coordination. It was hypothesized that small torso angles yield a forward shift of the muscle activation timing and crank torque. Twenty-one trained cyclists performed three exercise bouts at 70% maximal aerobic power in a time trial position at three different torso angles (0°, 8°, and 16°) at a fixed cadence of 85 rpm. Measurements included surface electromyography, crank torques and gas exchange. A significant increase in crank torque range and forward shift in peak torque timing was found at smaller torso angles. This relates closely with the later onset and duration of the muscle activation found in the gluteus maximus muscle. Torso angle effects were only observed in proximal monoarticular muscles. Moreover, all measured physiological variables (oxygen consumption, breathing frequency, minute ventilation) were significantly increased with lowering torso angle and hence decreased the gross efficiency. The findings provide support for the notion that at a cycling intensity of 70% maximal aerobic power, the aerodynamic gains outweigh the physiological/biomechanical disadvantages in trained cyclists.

This paper explores the results obtained from an innovative physical model study which examined wind induced forces and pressures on a 1:25 scale model of a Class 390 Pendolino at a 30° yaw angle. For the first time, the work considers in detail the differences between moving model experiments and static experiments. Differences between the static and moving experiments are observed in the pressure distribution on the nose region of the train, however over the rest of the train the differences between the two sets of experiments are within the experimental uncertainty. The overall side, lift and rolling moment coefficients acting on the train are also shown to agree. This paper provides the scientific underpinning embedded within the current industrial guidelines and once and for all, demonstrates that in terms of the overall mean aerodynamic side and lift forces and rolling moment coefficients, static experiments are sufficient.

To reduce aerodynamic resistance cyclists lower their torso angle, concurrently reducing Peak Power Output (PPO). However, realistic torso angle changes in the range used by time trial cyclists have not yet been examined. Therefore the aim of this study was to investigate the effect of torso angle on physiological parameters and frontal area in different commonly used time trial positions. Nineteen well-trained male cyclists performed incremental tests on a cycle ergometer at five different torso angles: their preferred torso angle and at 0, 8, 16 and 24°. Oxygen uptake, carbon dioxide expiration, minute ventilation, gross efficiency, PPO, heart rate, cadence and frontal area were recorded. The frontal area provides an estimate of the aerodynamic drag. Overall, results showed that lower torso angles attenuated performance. Maximal values of all variables, attained in the incremental test, decreased with lower torso angles (P 0.001). The 0° torso angle position significantly affected the metabolic and physiological variables compared to all other investigated positions. At constant submaximal intensities of 60, 70 and 80% PPO, all variables significantly increased with increasing intensity (P 0.0001) and decreasing torso angle (P 0.005). This study shows that for trained cyclists there should be a trade-off between the aerodynamic drag and physiological functioning.

Crosswinds have the potential to influence the stability and therefore the safety of a motorbike rider. Numerical computations using both delayed detached-eddy simulations (DDES) and Reynolds-Averaged Navier-Stokes (RANS) were employed to investigate the flow around a motorbike subjected to crosswinds with yaw angles of 15, 30, 60 and 90 degrees. The Reynolds number was 2.2 million, based on the crosswind velocity and the height of the rider from the ground. The aerodynamic force coefficients and flow structures around the motorbike and rider were obtained and analysed. Although both DDES and RANS provided comparable overall aerodynamic forces, RANS failed to predict both the DDES surface pressures at the separation regions and the location and size of the main circulation region. The DDES results showed that the drag coefficients decrease with increasing yaw angles, while the side force coefficients significantly increase. It was found that increasing yaw angles result in stronger vortex shedding around ...

The lodging of cereal crops due to high wind and rain is of considerable significance in many parts of the world, leading to major economic losses and yield reductions. In earlier papers the authors have developed a model of the lodging of winter wheat that identified the major parameters of the problem and enabled the relationship between root and stem lodging to be examined. It has formed the basis of a methodology used in the UK for guidance to farmers and agronomists on ways of reducing lodging risk. However the authors would be the first to acknowledge that there are limitations to the model that make it difficult to apply for a wide range of crops--particularly in the specification of the wind field and the root/soil interaction, and in allowing for stem lodging elsewhere than at the base of the stem. This paper thus describes the development of a generalised model that overcomes these shortcomings. After a discussion of the lodging phenomenon in general and a description of the earlier work, the basis of the new model is set out, based upon a mechanical model of the wind/plant/soil interactions that capture most of the important physical processes. The manner in which this model can be applied to clarify the nature of the lodging process and calculate lodging risk through a simple graphical formulation is discussed. In particular simple formulae are defined for lodging risk that are functions of a small number of dimensionless variables with identified physical meanings. The model is then applied to the lodging of wheat, oat and oilseed rape crops and considers the sensitivity of the risk calculations to uncertainties in the model parameters. In general it is suggested that the risk of lodging can be determined from very simple functions of dimensionless stem and root lodging velocities.

This is the first part of a two-part paper that describes the results of an experimental investigation to measure the aerodynamic pressure forces on structures in the vicinity of railway tracks. The investigations were carried out in order to obtain a fundamental understanding of the nature of the phenomenon and to obtain data for a variety of railway infrastructure geometries of particular relevance to the UK situation, in order to provide material for a National Annex to the relevant Eurocode. The experiments were carried out on the moving model TRAIN Rig, with models of three different sorts of trains with different nose types, and a variety of infrastructures types: vertical hoardings, overbridges, station canopies and trestle platforms. The transient loads that were measured had a characteristic form: a positive pressure peak followed by a negative pressure peak. In general the magnitudes of the two peaks were different, and varied with infrastructure type and position, as well as with train type. As would be expected, the more streamlined the train, the lower were the magnitudes of the pressure transients. A comparison of the experimental results was made with a variety of existing model- scale and full-scale data and a broad consistency was demonstrated, within the limits that the rather different experimental conditions in the various cases would allow. An analysis of the scaling of these pressure transients was carried out, and it was shown that whilst there was a reasonable coalescence around a theoretical formulation, the complexity of the flows involved meant that a general scaling formulation could not be achieved. Part 2 of this paper will consider the application of the results to the development of revised standards formulations.

The aims of this research were to firstly investigate the effect of crosswinds on the aerodynamic behaviour of cyclists and secondly, to determine which parameters (cyclist position and bike type) influenced the aerodynamic forces on cyclists the most. The aerodynamic response of two different full-scale bikes with and without a mannequin has been recorded for a variety of crosswind angles ranging from 0 o – 90 o (in 15 o increments). The results showed that the wind induced force is a function of the crosswind angle. The actual aerodynamic loads arising from such winds can be up to about 2.5 times the aerodynamic drag. It has also been observed that the torso angle has little effect on the lateral force coefficient. In contrast, the bike type significantly affects the aerodynamic forces: at large yaw angles, a road bike is responsible for approximately 60% of the total lateral force coefficient. This study is the first step in the process of determining the effect of crosswind from a full range of angles of attack on cyclists, and will help to improve the safety of cyclists and equipment, and to define guidelines for cycling lanes.

Costas arrays are special permutation patterns with various applications in communications and signal processing. Their construction is a difficult combinatorial problem and only a handful of constructions are known. Little is known about those arrays that are not generated by the existing methods. This paper presents an algorithm for the construction of sequences that obey the distinct difference constraints imposed by the Costas array problem. The algorithm is based upon the abstract linear dependence properties of various sets of simple integral vectors and their permutations. The algorithm shows that the entire Costas array problem is most naturally expressed in terms of a simple stack data structure. Simulations of the algorithm are evaluated with a linearity metric on the sequences produced.

The concept of autonomous road vehicles has recently gained a great deal of technical respectability. Expected advantages over normal driver-controlled vehicles are through increased safety, reliability and fuel efficiency. This paper presents a novel experimental study enabling for the first time a full understanding of the aerodynamic flow development of a long vehicle platoon. Moving model experiments were carried out at the University of Birmingham Transient Aerodynamic Investigation (TRAIN) rig facility on a 1/20th scale eight lorry platoon with three constant vehicle spacings. Slipstream velocity and pressures, as well as simultaneous on-board vehicle surface pressure measurements were made. Results indicated a highly turbulent boundary layer development, with slipstream pulse peaks near the front of each lorry; similar to previous findings on flows around container freight trains. The drag coefficient of an isolated lorry was in agreement with previous studies. There are substantial reductions in aerodynamic drag for the non-leading platoon vehicles. Drag results plateaued towards a constant value within the platoon. Vehicle spacing affected drag values, with decreases of 57% observed for the closest spacing of half a vehicle length, demonstrating the aerodynamic benefits of platooning.

In recent years, the concept of autonomous road vehicles has gained a great deal of technical respectability, with expected fuel benefits arising from running vehicles closely in platoons. However, the aerodynamics of such vehicles travelling in close proximity is still not understood. This paper presents for the first time a detailed study of drag benefits and the flow structure around a platoon of high-sided lorries, through conducting Delayed Detached Eddy Simulations (DDES). The lorry surface pressure and slipstream flow characteristics show good agreement with experimental data. Drag reductions of up to 70% have been observed for all trailing lorries in the platoon. Analysis of the flow field indicated highly turbulent regions on the top and sides of trailing lorries. Turbulent kinetic energy and Reynolds stresses were found to concentrate at the connection region between lorry cab and box. Spectral analysis of the side forces identified oscillating behaviour on each lorry in the platoon due to strong vortex shedding, suggesting that platooning lorries are potentially more likely to develop lateral instabilities than an isolated lorry. The study indicates that autonomous vehicle developers and operators should consider the significant drag reduction benefits of platooning against the risk associated with potential lateral instabilities.

We propose a new information theoretic approach to understanding analog-to-digital (A/D) conversion principles. An A/D converter is characterized as a communication system that transmits information from an analog source to the digital domain for processing, storage, transmission, and analysis. Accordingly, an A/D conversion system consists of an analog source of information, a means to sample and encode the analog signal for transmission through the comparator, and a means to decode the digital output from the comparator and provide a digital representation of the analog signal. The comparator acts as a channel since it “injects” uncertainty in the form of quantization noise. We provide an upper bound (conversion capacity) on the amount of information that can be transmitted from the analog to digital domain for a specific A/D converter and we describe a necessary and sufficient condition that, if satisfied, allows an A/D converter to achieve capacity. The conversion capacity defines a fundamental upper limit on the performance of an A/D converter in terms of resolution-bandwidth product for a given technology. It is shown how the conversion capacity may be utilized to yield performance limitations in terms of mean square error and SNR. The capacity is, thus, a useful metric for the comparison of ADC designs and may also provide hints to improving existing and conceiving new A/D conversion methods.

The experimental investigation of turbulence has been greatly aided by the development of instruments capable of measuring and recording instantaneous velocity measurements at high frequencies, such as Laser Doppler and Acoustic Doppler Velocimeters. As a consequence of the techniques and algorithms used by some of these instruments, the introduction of ‘spikes’ of invalid data into the recorded velocity time-series is inevitable, with resulting errors in the calculated turbulence characteristics. These spikes should, therefore, be removed and replaced with statistically valid values if power spectra and parameters such as turbulence intensity are to be examined. A number of existing spike detection and replacement methods are discussed and combinations of these have been applied to data from a variety of sources—artificially corrupted test data, data from laboratory experiments in a flume and data from field experiments in a natural river. Earlier recommendations, based on studies using a smaller number of despiking methods and data sources, are improved; contrary to previous findings, Phase – Space Thresholding is shown to accurately reconstruct the power spectrum when used with the appropriate replacement method.

Physical and numerical simulations of open channel flow over a heterogeneously roughened bed are examined. The velocity field is mapped at four different cross sections by using an acoustic Doppler velocimeter and the boundary shear stress obtained from both the velocity data and application of a Preston tube. These data illustrate that in the current arrangement the roughness elements dominate the physics of the flow and act as a source of vorticity, which is initially manifested as local boundary shear stress and, in turn, affects the secondary flow structures and momentum transfer in the channel. This paper presents the first attempt at using the Shiono–Knight method to model velocity and boundary shear stress distributions in a heterogeneous open channel. Appropriate advice concerning values of calibration parameters and discretization of the cross section is given. The combined physical/numerical approach provides an insight into the changing properties of the flow structure within a nonunifo...

This paper examines the velocity field in an idealised heterogeneous open channel during normal flow conditions, corresponding to two different subcritical flow conditions (discharges of 0·040 m3/s and 0·056 m3/s, with corresponding Froude numbers 0·51 and 0·57). The bed of the channel is formed of two full-length, longitudinal strips of equal width, a smooth section constructed from polyvinyl chloride and a rough section constructed from gravel (d72 = 10 mm). The results indicate that the turbulence appears to propagate vertically from the rough bed and horizontally over the rough–smooth boundary. There is also evidence to suggest that the turbulent momentum transfer is maximised at the rough–smooth boundary. Secondary flow structures are seen to exist due to the rough–smooth boundary and provide another mechanism for momentum transfer. These transfer mechanisms are important in understanding the effect of a heterogeneous channel bed on open-channel flow.

Traditionally, a quasi steady response concerning the aerodynamic force and moment coefficients acting on a flat plate while \'flying\' through the air has been assumed. Such an assumption has enabled the flight paths of windborne debris to be predicted and an indication of its potential damage to be inferred. In order to investigate this assumption in detail, a series of physical and numerical simulations relating to flat plates subject to autorotation has been undertaken. The physical experiments have been carried out using a novel pressure acquisition technique which provides a description of the pressure distribution on a square plate which was allowed to auto-rotate at different speeds by modifying the velocity of the incoming flow. The current work has for the first time, enabled characteristic pressure signals on the surface of an auto-rotating flat plate to be attributed to vortex shedding.

This paper presents the results obtained from a series of wind tunnel experiments undertaken in order to assess (and improve) the operation of a generic long span bridge subjected to strong winds (the operation of the bridge is evaluated in terms of the aerodynamic loads on a number of vehicles—in all cases the mean crosswind is greater than or equal to 10 m/s). The aerodynamic loads, in terms of mean and peak side and lift force coefficients and rolling moment coefficient are presented for three 1:40 scale model vehicles placed on the bridge: a Van, a Bus and a Lorry. These vehicles were tested under static conditions (i.e., the motion between the vehicle and the bridge deck was not simulated), and subjected to a uniform turbulent crosswind at different incoming directions. Two separate bridge deck scenarios were examined—an ‘Ideal’ and a ‘Typical’ deck shape. The data show a good agreement with the findings of previous research with respect to the ‘Ideal’ bridge geometry. The Typical bridge section enables the differences between the idealised bridge and a more realistic deck geometry to be explored. The work indicates that the Lorry, rather than the Van or the Bus, is the critical vehicle in terms of overturning stability (as characterized by the highest magnitudes of the rolling moment coefficient). An approximately linear decrease of the side force and rolling moment coefficients is found on the Typical deck when the vehicle is positioned at a progressively larger distance from the windward edge. The research provides novel data and interpretation on the aerodynamic loads experienced by road vehicles.

The present paper reports the findings of a study in which the appropriateness of using two-dimensional (2D) and three-dimensional (3D) numerical modelling in order to simulate the flow in a small reach of the river Blackwater, UK, was examined. The numerical simulations were compared with data obtained from a 1 : 5 scale physical model of the reach. A variety of turbulence models were used in order to evaluate their suitability and assess their impact on the simulations. In order to enable direct comparisons, all of the simulations were undertaken using a single modelling code, Delft3D. It was shown that 3D models offer significant advantages over 2D when applied to a meandering channel and that this choice outweighs the choice of turbulence model.

Building on previous work where fluorescence spectroscopy has been used to detect sewage in rivers, a portable LED spectrophotometer was used for the first time to establish bacterial numbers in a range of water samples. A mixed-method approach was used with standard bacteria enumeration techniques on diluted river water and sewage works final effluent using a number of diluents (Ringer's solution, tap water and potable spring water). Fluorescence from uncultured dilutions was detected at a 280 nm excitation/360 nm emission wavelength (corresponding to the region of tryptophan and indole fluorescence) and compared with bacteria numbers on the same cultured sample. Good correlations were obtained for total coliforms, E. coli and heterotrophic bacteria with the portable LED spectrophotometer (R2 = 0.78, 0.72 and 0.81 respectively). The results indicate that the portable spectrophotometer could be applied to establish the quality of drinking water in areas of poor sanitation that are subject to faecal contamination, where infrastructure failure has occurred in the supply of clean drinking water. This would be particularly useful where laboratory facilities are not at hand.

This paper presents a method for predicting the lateral distribution of depth-averaged streamwise velocity in straight prismatic open channels with emergent vegetation. The approach is fully consistent with the original Shiono and Knight method of analysis, and extends it to include the drag force due to vegetation, modelled as an additional momentum ‘sink' term, with the blockage effect of the vegetation modelled by way of a porosity analogy. An analytical solution to the depth-integrated Reynolds-averaged Navier–Stokes equation is given which includes the effects of bed friction, drag force, lateral turbulence and secondary flows, governed by four coefficients f, CD, λ and Γ respectively. The analytical results are shown to predict the lateral distributions of depth-averaged velocity well for three sets of experimental data: one for inbank flow in a partially vegetated channel and two for overbank flows in compound channels with partially vegetated floodplains. The analytical solution is also shown to give identical results to numerical simulations of the same governing Reynolds-averaged Navier–Stokes equation applied to some experiments undertaken in the UK Flood Channel Facility. The lateral distribution of bed shear stress is also obtained through the Darcy–Weisbach friction factor, thus providing a basis for modelling flood conveyance, fluvial processes and eco-environmental impacts in natural rivers.

The following work explores the possibility of applying an evolutionary algorithm (NSGA-II) to automate the calibration procedure of a quasi 2-D numerical model. Seven rivers are examined, with discharges and flow depths ranging from 6 to 450 m 3 /s and 0.49 to 3.69 m, respectively. The calibration procedure is based on matching lateral distributions of depth-mean velocity, for which data exist. The results are compared with simulations undertaken by an expert user using traditional calibration techniques. The new approach compares favourably with the expert user and is able to provide an insight into the optimum calibration parameters, from which further scientific knowledge could be developed.

This paper presents a theoretical model based on the free vortex theorem that is capable of predicting the pressure head distribution at the brink of free overfalls in open channels. This approach is coupled with the momentum equations to obtain the end-depth-ratio (EDR) from which the discharge can be estimated. In order to illustrate its flexibility, the theory is successfully applied to flat-based circular and U-shaped channels. Using previous experimental data, the proposed method is validated.

Stem and root lodging constitute significant adversities to sunflower (Helianthus annuus L.) cropping in Argentina. We have adapted previously developed models of the lodging process in cereals to the particularities of sunflower by using functions, developed using data obtained by mechanical lodging, for the [root failure moment/plant anchorage] and [stem failure moment/thickness of stem wall] relationships, and estimates of plant area loaded by wind gusts. The model uses this information to estimate wind failure speed (i.e., the wind speed at which lodging [stem or root, as appropriate] is expected to occur). The model was tested against information (plant and soil characteristics, measured wind gust velocity immediately preceding rainfall) obtained in 26 naturally lodged plots (6 stem-lodged, 20 root-lodged) which occurred across a network of trials (2 seasons, 4 sites, 3 hybrids, 4 crop population densities, all experiments fitted with automatic meteorological stations). Lodging events took place over a range of crop developmental stages between visible capitulum and harvest maturity. Lodging index (proportion of plants lodged) against the difference between observed and model-estimated wind failure speeds showed that the model had good predictive skill across the range of conditions explored in these experiments and was able to distinguish between hybrids of differential susceptibility to lodging within the same experiment. Sensitivity analyses showed that the principal determinants of lodging susceptibility were root plate diameter, stem wall thickness, and the area of the plant loaded by wind gusts. Within the observed ranges (almost twofold) of stem height and stem natural frequency, these two variables had little influence on lodging susceptibility. We conclude that the model, despite the simplifications incorporated into its structure, provides an effective and useful tool for the integration of the complex factors that determine lodging susceptibility in this species. Fil: Sposaro, M.M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Berry, P.M.. ADAS; Reino Unido Fil: Sterling, M.. University of Birmingham; Reino Unido Fil: Hall, Antonio Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Chimenti, Claudio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina

This paper considers whether the application of principal component analysis to a free overfall in an open channel can yield any further insights into the variables which govern the relationship between the depth of flow at the start of the free overfall and the critical depth. It is shown that for a channel of rectangular cross-section, the width, the end depth, the square root of bed slope and the square root of the critical slope can be considered to be the primary variables of interest. While a possible relationship between these variables is suggested, it is noted that the precise form of the relationship is beyond the abilities of principal component analysis.

This paper describes the use of coupled Computational Fluid Dynamics (CFD) and Rigid Body Dynamics (RBD) in modelling the aerodynamic behaviour of wind-borne plate type objects. Unsteady 2D and 3D Reynolds Averaged Navier-Stokes (RANS) CFD models are used to simulate the unsteady and non-uniform flow field surrounding static, forced rotating, auto-rotating and free-flying plates. The auto-rotation phenomenon itself is strongly influenced by vortex shedding, and the realisable k-epsilon turbulence modelling approach is used, with a second order implicit time advancement scheme and equal or higher order advection schemes for the flow variables. Sequentially coupling the CFD code with a RBD solver allows a more detailed modelling of the Fluid-Structure Interaction (FSI) behaviour of the plate and how this influences plate motion. The results are compared against wind tunnel experiments on auto-rotating plates and an existing 3D analytical model.

In this paper, genetic programming (GP) is used as an effective model induction tool to solve a classic problem in open channel flow: the free overfall. By applying GP to experimental data of circular channels with a flat bed and employing a model selection procedure, a reliable expression in the form of is found for calculating the critical depth (hc) and end-depth ratio (EDR). Further effort is made to verify the applicability and superiority of this expression for channels with other cross sections. This global expression not only outperforms other expressions in estimating the critical depth, it is also dimensionally correct (unlike some other applications of GP) and can be used for channels with any cross-section and any flow regime.

This paper examines the wind induced forces and moments experienced by a high sided lorry. Full-scale measurements are combined with wind tunnel and CFD simulations in order to gain an insight into the flow field around the vehicle. Differences and similarities between the three techniques are noted. It is shown that the rolling moment coefficient obtained from full-scale measurements and CFD simulations agree consistently across a wide range of yaw angles. With respect to the side force coefficient, good agreement between the wind tunnel and full-scale data are achieved. Pressure distributions over selected sections of the lorry reveal that despite good agreement with the overall forces, the localised pressure field can be significantly different.

Increasing train speeds combined with the predicted reduction in the weight of new trains ensure that the effect of crosswinds on train stability is of continued interest to the rail industry. Changes in the approaching wind velocity can in turn lead to changes in both the lift and side force on a vehicle. Calculations of the wind induced force can either be undertaken in the frequency domain with knowledge of aerodynamic admittance characteristics or in the time domain using aerodynamic weighting functions. This paper investigates the applicability of developing a universal aerodynamic admittance function and a corresponding analytical weighting function for a variety of train types based on a range of experimental data. It is suggested that only two variables are required to parameterise both the admittance and weighting functions. It is also argued that for certain train types one of these variables can be considered as a constant across a wide range of yaw angles.

This article develops two relatively simple models that are combined in order to model the response of a standing person to a passing train. The first model combines potential flow theory, boundary layer theory, and autoregressive modelling in order to simulate the slipstream of a passenger train. The second moment simulates the response of a person to the wind velocities generated in the slipstream model. For the first 0.375 s the person is assumed to respond as a solid object, whereas after this time a spring—mass—damper system is used to represent the response of a person. A Monte Carlo analysis is used in order to establish the probability of a person becoming destabilized as a result of increasing train speed. Finally, a parametric analysis is undertaken and illustrates that the output of the models that represent the response of a person is sensitive to the parameter values chosen.

Some practical and theoretical concepts related to the use of an acoustic Doppler current profiler (ADCP) in a small river are examined. The importance of understating the limitations of the measurement equipment and a system for locating the exact position of the ADCP are discussed. Details of a new measurement protocol which is suitable for small rivers are presented. Small samples of data measured in the River Blackwater are used to illustrate the concepts outlined in the paper. It is concluded that ADCPs can be successfully used in small rivers provided sufficient care is taken over their deployment and subsequent data analysis. However, in some cases it is acknowledged that additional modifications to the ADCP may need to be undertaken as illustrated in the paper.

This paper outlines the results of a physical simulation (at a 1:700 - 1:1000 geometric scale) of a thunderstorm downburst. Three different methods are examined in order to generate the time dependent nature of a downburst: directly controlling the fans and via two different types of opening apertures. Similarities are shown to exist between each method, although the results obtained from one approach are favoured since they appear to be independent of the downdraft velocity. Significant run-to-run variations between each experiment are discovered and in general it is found beneficial to interpret the results in terms of 10 run ensemble averages. An attempt to simulate a translating downburst is also undertaken and the results are shown to compare favourably with full-scale data.

The Shiono and Knight method (SKM) is a simple depth-averaged flow model, based on the RANS equations which can be used to estimate the lateral distributions of depth-averaged velocity and boundary shear stress for flows in straight prismatic channels with the minimum of computational effort. However, in order to apply the SKM, detailed knowledge relating to the lateral variation of the friction factor (f), dimensionless eddy viscosity (λ) and a sink term representing the effects of secondary flow (Γ) are required. In this paper a multi-objective evolutionary algorithm is used to study the lateral variation and value of these parameters for simple trapezoidal channels over a wide range of aspect ratios through the model calibration process. Based on the available experimental data, four objectives are selected and the NSGA-II algorithm is applied to several datasets. The best answer for each set is then selected based on a proposed methodology. Rules relating f, λ and Γ to the wetted parameter ratio (Pb/Pw) for a variety of situations have been developed which provide practical guidance for the engineer on choosing the appropriate parameters in the SKM model.

This paper examines the use of data obtained from large eddy simulations in exploring the instantaneous characteristics of boundary shear stress. The probability density functions (PDF) of the shear stress are shown to be non-Gaussian, whereas the PDF of the shear force per unit length is found to be approximately Gaussian. Conditional sampling is used in order to provide an insight into the average behavior of an extreme shear stress event. Finally, proper orthogonal decomposition illustrates that the behavior of the shear stress is complex and cannot necessarily be attributed to a single major flow event.

The response of an individual to a sudden increase in wind velocity is important in terms of wind comfort and wind safety. This paper is concerned with the latter issue and outlines a series of physical and numerical experiments undertaken in order to evaluate the response of an individual to a sudden change in wind speed. The physical experiments were undertaken in the dynamic circuit of the Jules Verne Climatic Wind Tunnel at CSTB in Nantes, France and subjected 31 people to wind speeds up to 20 m/s. In all cases the wind speed increased from a mean value of zero to the target value in approximately 0.2 s. The wind speed required to cause loss of balance is shown to be a function of orientation and weight. In an attempt to understand the influence that gust frequency and mean velocity exert on wind safety criteria, a simple numerical model has been developed. The model is shown to agree reasonably well with the data pertaining to the physical experiments. Furthermore the model has been used in a predictive sense to evaluate response of a 50th percentile child to sudden changes in wind speed. It is shown that such a child is potentially very wind sensitive, with 30% reduction in the wind velocity required to cause loss of balance when compared to the 50th percentile adult male.

Outdoor human comfort in an urban environment may be affected by a wide range of weather and human factors. The paper describes a research study investigating the complex relationship between physical and psychological parameters on human comfort levels. The study determined that the air temperature and the wind speed have a clear influence on the human comfort level while the solar radiation and relative humidity do not show a strong relationship. The effects of adaptation were shown clearly using over 8000 data sets with clear differences between five European countries. The importance of adaptation was further shown by the low correlation values between comfort and certain meteorological parameters. It is suggested that the subjective parameter of human comfort level is not well suited to determine guidelines for the design of outdoor spaces. Controlled tests in a wind tunnel have shown that the skin temperature (forehead and hand) has the potential to be used as a surrogate for comfort. With respect to the climatic variations outlined in this paper, it was discovered that lower forehead temperatures resulted in lower comfort values nearly independent of the meteorological parameters. Therefore, in the current study it is found that the skin temperature may be used as an objective parameter to determine human outdoor comfort levels although further tests will be necessary.

As the speeds of both passenger and freight trains increase, there is increasing concern that the unsteady gusts generated in train boundary layers and wakes will become more of for a risk to passengers waiting on platforms and for trackside workers. In addition, the demands of interoperability make this a problem of growing relevance to railway operators across Europe. A number of model scale and full-scale experiments have been carried out in recent years that have provided robust experimental data to quantify these flows. This paper considers all the available datasets for high-speed passenger trains and container freight trains, and in making a comparison between them, arrives at a number of conclusions concerning the characteristics of train slipstreams. It is concluded that the identification of a number of distinct flow regions in earlier work is generally valid and forms a useful framework for the consideration of the problem. The flow characteristics are different in each region, and, depending upon the train type, the measurement distance from the train and height above ground, the observed peak gusts for a train may occur at any time during the train passage or in its wake. It is also concluded that results obtained from measurements around small scale moving models are in good agreement with the full scale measurements and reproduce all the important flow features.

Full-scale measurements were undertaken on a commercial vehicle in the atmospheric boundary layer in order to establish the variation in rolling moment coefficient with yaw angle. Both moving and stationary experiments were undertaken and it is shown that for the purposes of the current analysis it is sufficient to neglect the motion of the vehicle. Two approaches were used to determine the rolling moment on a stationary vehicle: direct measurement using load cells, and indirect measurement obtained from the integration of vehicle surface pressures. Results obtained using both methods are shown to agree within acceptable limits. The aerodynamic admittance of the rolling moment was also investigated and is shown to be a function of the yaw angle. Furthermore, the importance of the lateral velocity component on the aerodynamic admittance is illustrated. Finally, the peak values of the rolling moments are evaluated and are found to illustrate non-Gaussian behaviour.

Background: Symptom monitoring is a cornerstone of asthma self-management. Conventional methods of symptom monitoring have fallen short in producing objective data and eliciting patients’ consistent adherence, particularly in teen patients. We have recently developed an Automated Device for Asthma Monitoring (ADAM) using a consumer mobile device as a platform to facilitate continuous and objective symptom monitoring in adolescents in vivo. Objective: The objectives of the study were to evaluate the validity of the device using spirometer data, fractional exhaled nitric oxide (FeNO), existing measures of asthma symptoms/control and health care utilization data, and to examine the sensitivity and specificity of the device in discriminating asthma cases from nonasthma cases. Methods: A total of 84 teens (42 teens with a current asthma diagnosis; 42 without asthma) aged between 13 and 17 years participated in the study. All participants used ADAM for 7 consecutive days during which participants with asthma completed an asthma diary two times a day. ADAM recorded the frequency of coughing for 24 hours throughout the 7-day trial. Pearson correlation and multiple regression were used to examine the relationships between ADAM data and asthma control, quality of life, and health care utilization at the time of the 7-day trial and 3 months later. A receiver operating characteristic (ROC) curve analysis was conducted to examine sensitivity and specificity based on the area under the curve (AUC) as an indicator of the device’s capacity to discriminate between asthma versus nonasthma cases. Results: ADAM data (cough counts) were negatively associated with forced expiratory volume in first second of expiration (FEV 1 ) ( r =–.26, P =.05), forced vital capacity (FVC) ( r =–.31, P =.02), and overall asthma control ( r =–.41, P =.009) and positively associated with daily activity limitation ( r =.46, P =.01), nighttime ( r =.40, P =.02) and daytime symptoms ( r =.38, P =.02), and health care utilization ( r =.61, P

Thunderstorm downbursts are transient, small-scale events which are, however, the cause of design wind speeds in many parts of the world. The difficulties in predicting when and where such events will occur make capturing full-scale wind loading data for buildings particularly difficult, and so attention has turned to physically simulating downburst flow fields in the laboratory. The University of Birmingham Transient Wind Simulator (UoB-TWS), a 1 m diameter, pulsed impinging jet facility, has been used to physically simulate a downburst and measure the wind-loading on building models which occurs. For the first time, pressure data have been recorded over both single and multiple building model arrangements, allowing interference effects to be quantified. It is demonstrated that the presence of another building nearby can increase drag coefficients by almost 40%, depending on the separation of the building models and the angle of the wind relative to the models.

Lodging in barley (Hordeum vulgare L.) can result either from buckling of any part of the stem (stem lodging) or failure of the root–soil anchorage system (root lodging). A framework for calculating the risk of stem lodging is developed which takes account of the shoot's height, ear area, natural frequency, weight, the flexural rigidity of the stem and changes in stem strength along its length. The model predicted that stem lodging in barley cultivars would occur half way up the stem, and stem lodging in wheat would occur close to the soil surface. These predictions are consistent with general observations of stem lodging in barley and wheat. The higher position of stem lodging in barley, compared with wheat, was caused by the greater flexibility of the barley stems and a more rapid reduction in stem strength up the stem. A sensitivity analysis showed that the stem diameter of the middle internodes had the greatest effect on the risk of stem lodging. Changes to ear area, drag coefficient, crop height, shoot natural frequency and the strength of the stem wall had a moderate influence. Measurements of anchorage strength in barley and wheat plants indicated that the mechanism of anchorage failure was the same for both species and that a model of root lodging developed for wheat could be successfully adapted for barley.

Lodging resistance ratings for winter wheat cultivars are frequently based upon observations of lodging. This is an unreliable method because of the frequent occurrence of years without significant lodging events. It also does not distinguish between stem and root lodging resistance. This paper describes the development and testing of instrumentation and procedures for two field-based methods to rapidly assess stem and root lodging resistance. Both methods used a specifically designed instrument for measuring the resistance of shoots against rotational displacement. Stem lodging resistance was assessed when the soil was dry and strong, whereas resistance to root lodging was assessed after the soil had been weakened by irrigation. Tests were carried out on 14 winter wheat cultivars grown at two sites in the UK during 2002. Both methods were able to detect statistically significant differences between the cultivars for their resistance to stem and root lodging. A comparison of these results with observations of lodging in the field showed that the methods accounted for about 60 and 50 % of the stem and root lodging respectively.

This paper describes an investigation into the fundamental nature of the wheat (Triticum aestivum L.) lodging process, which was carried out to obtain data to help develop a theoretical model of the lodging process. To enable realistic soil/root systems to be investigated in controlled conditions, a portable wind tunnel was constructed that could be placed over crops of various types in various soil conditions. This paper reports a calibration of this wind tunnel against natural conditions and shows that in many respects a good simulation of the natural wind over a crop was achieved, but that the precise structure of the atmospheric turbulence was not fully represented. Measurements of plant characteristics showed significant variations of natural frequency of plant oscillation during the season, and for different levels of crop wetting. Both stem and root lodging were observed within the wind tunnel. The former was found to occur instantaneously, whilst the latter developed over a period of minutes. The damping of individual shoots is shown to be high with damping ratio estimated at 0.08 and to be unaffected by variation in plant types and soil conditions. The plant drag coefficient is determined through strain gauge measurements and is shown to be of the order of unity. Overall the results suggest that the existing theoretical model is adequate in most aspects, but needs to be refined in others, particularly with regard to the progressive failures observed in the root lodging process.