Full-scale Observations Research Articles

Mixing and transport in urban areas

Concern over terrorist releases of harmful material has generated interest in short-range air-borne dispersion in urban areas. Here, we review the important fluid dynamical processes that control dispersion in the first kilometre, the neighbourhood scale, when much of the material remains within the urban canopy. Dispersion is then controlled by turbulent mixing and mean flow transport through the network of streets. We consider mixing and transport in a long straight street, street intersections and then a network of streets connected by intersections. The mixing and transport in these systems are illustrated with results from recent fine-resolution numerical simulations and laboratory models, which then inform simpler scaling estimates and modelling schemes. Finally, we make some tentative steps to pull the process studies together to begin to understand results from full-scale observations. In particular, it is shown that the positions of 'shear layers' and 'dividing streamlines' largely control the patterns of mixing and transport. It is also shown that neighbourhood-scale dispersion follows one scaling in the near field and another in the far field after passage through many intersections. The challenge for the future is to bring these threads together into a coherent mathematical model.

Dynamics and radar cross section density of chaff clouds

A new chaff cloud model (CCM) is described which is based on fundamental principles with modifications based on laboratory observations. Excellent approximations to the exact physical model have been developed which can rapidly predict the chaff fiber density and orientation as a function of location, time and fiber characteristics. Using this information, the time varying radar cross section (RCS) density is determined for any frequency and polarization anywhere within the chaff cloud. The results are consistent with full scale observations, and the computational speed allows the model to be integrated into existing real time radar simulations.

Comparison of wind pressure measurements on tower-like structure obtained from full-scale observation, wind tunnel test, and the CFD technology

Full-scale measurements, wind tunnel tests and CFD calculations have been carried out on pressure measurements on a tower-like structure. This paper presents the comparison of pressure measurements among these three methods. The mean wind pressure coefficients obtained from the wind tunnel tests are fairly close to those of the full-scale measurements after the reference pressure is taken into consideration. RMS wind pressure coefficients obtained in the wind tunnel tests were smaller than those in the full-scale measurements. In the application of the results of wind tunnel test to real designs, at least the turbulent intensity of approaching wind should be taken into consideration, at least. As regards mean wind pressure coefficients of the comparisons among the three methods, CFD calculated results showed good agreement with those of wind tunnel tests and full-scale.

SE—Structures and Environment: Effect of Ventilator Configuration on Wind-driven Ventilation in a Crop Protection Structure for the Tropics

A laboratory method for studying wind-driven natural ventilation was applied to a single-span greenhouse with side-wall and roof ventilation openings, a design common to crop protection structures used in tropical countries. A 1:15 scale model replica of the greenhouse, made from clear Perspex, was immersed in a flume tank filled with water. A steady mean flow generated by the flume simulated wind flow past the model. The flow inside the model greenhouse was examined for four different ventilator configurations and ventilation flow rates compared in each case. Neutrally-buoyant particles seeded in the flow allowed for clear flow visualization and these particles were tracked using a digital image analysis system from which detailed velocity measurements were obtained. Flow patterns observed in the scale model agree qualitatively well with full-scale observations. Predictions of the flow at full scale inferred from measurements of pressure and flow speed made at the side-wall openings of the model differed by less than 10% and 28%, respectively, from measurements made in the full-size greenhouse. For all ventilator configurations using side-wall openings an incoming jet-like flow crossed the greenhouse and established a circulating flow. The greenhouse with roof ventilation only had the lowest ventilation rate and the maximum rate was achieved with combined side-wall and roof openings. The results of these studies are detailed and design recommendations to improve the ventilation of tropical greenhouses are suggested.

A method for routine characterisation of shelterbelts

This paper describes a working method of assessing the shelter quality of a wind-break, hedge or shelterbelt by a single field measurement, using portable equipment, deployed by an operative with minimal training on any day when the wind is suitable. The automated measurement yields a single characterisation parameter used to access an “expert system” database of information quantifying the benefit to plants or animals of various species. Because shelter depends not just on wind-break porosity but also on other local terrain features affecting the shear and turbulence in the upstream wind, the characterisation measurement is defined to include not only the mean wind speed but also the turbulence. Thus, the assessment of a farm hedge views the shelter benefit, not just of the hedge in isolation, but of the hedge as found within its own local surroundings. The routine measurement requires the simultaneous deployment of two anemometers connected to a pre-programmed data logger. One anemometer is sited upstream of the shelter barrier and one downstream. Both are at a distance h from the nearest shelterbelt face and at a height of 0.4 h, where h is the nominal height of the shelterbelt. The method is established by a combination of field and wind tunnel measurements. In the field, the shelter parameter has been measured for a hawthorn hedge and the flow downstream has been explored extensively. In the wind tunnel, a wind-break model has been constructed to reproduce the same shelter-parameter value, and the downstream flow compared extensively with the full-scale observations. Thus validated, the range of wind tunnel study has been extended to include other wind-break models and wind flow simulations giving a range of shelter parameters. The research was sponsored by, and the exploitation rights are the property of, Woodland Improvement and Conservation, of Huntley, Gloucestershire.

Evaluation of a Gaussian-modified dispersion model for atmospheric release from the Marcoule nuclear site

This paper presents a mathematical model of local pollutant dispersion designed to compute the concentration field above and around the Marcoule nuclear site. The model is based on integrating the classical turbulent diffusion equation, corrected (prior to integration) by experimental wind tunnel data obtained for a scaled-down model of the site. The computed results are compared with full-scale experimental observations at Marcoule in the case of neutral atmosphere. A comparison with the standard Gaussian model is also made. Finally, a critical analysis of the model is presented.

Optimizing Biological Nutrient Removal in anoxic zones

During the initial years of the development of Biological Nutrient Removal (BNR) technology, it was assumed that the bacterial species responsible of the removal of phosphorus (BioP organisms) could not use nitrates as a final electron acceptor and could thus not denitrify. The carbon taken up in the form of Volatile Fatty Acids (VFA) in the anaerobic zone was thus deemed to be unavailable for denitrification in the anoxic zone. This was reinforced through experiments in which BioP organisms cultured in the high-rate Phoredox system in which no nitrification took place, did not denitrify when nitrates were added. Many researchers (e.g. Dold and Barker) have since shown that in BNR systems such as the 3-Stage Bardempho system, where nitrates are recycled to the anoxic zone which follows the anaerobic zone, a high degree of phosphorus uptake through denitrification does occur. In addition, the partial diversion of primary effluent directly to the anoxic zone has significantly improved phosphorus uptake under anoxic conditions. Full-scale operations at the Westbank, British Columbia, plant showed a substantial uptake of phosphorus in the anoxic zone in the absence of oxygen. The Westbank configuration includes side stream primary sludge fermentation, VFA rich fermenter supernatant addition directly to the anaerobic zone and diversion of a portion of primary effluent to the anoxic zone. This configuration stimulates P-uptake under anoxic conditions, demonstrates the efficient use of carbon and is instrumental in achieving an annual average effluent Total-P concentration of less than 0.17 mg/l. The phenomenon of denitrification by BioP organisms was included in the Biowin Model developed by Dold (Biowin Manual). This paper describes experiments and full-scale plant observations to establish the role of BioP organisms in the removal of nitrates in the anoxic zone of a plant which also receives a portion of the primary effluent and verification of the Biowin model.

Optimizing biological nutrient removal in anoxic zones

During the initial years of the development of Biological Nutrient Removal (BNR) technology, it was assumed that the bacterial species responsible of the removal of phosphorus (BioP organisms) could not use nitrates as a final electron acceptor and could thus not denitrify. The carbon taken up in the form of Volatile Fatty Acids (VFA) in the anaerobic zone was thus deemed to be unavailable for denitrification in the anoxic zone. This was reinforced through experiments in which BioP organisms cultured in the high-rate Phoredox system in which no nitrification took place, did not denitrify when nitrates were added. Many researchers (e.g. Dold and Barker) have since shown that in BNR systems such as the 3-Stage Bardempho system, where nitrates are recycled to the anoxic zone which follows the anaerobic zone, a high degree of phosphorus uptake through denitrification does occur. In addition, the partial diversion of primary effluent directly to the anoxic zone has significantly improved phosphorus uptake under anoxic conditions. Full-scale operations at the Westbank, British Columbia, plant showed a substantial uptake of phosphorus in the anoxic zone in the absence of oxygen. The Westbank configuration includes side stream primary sludge fermentation, VFA rich fermenter supernatant addition directly to the anaerobic zone and diversion of a portion of primary effluent to the anoxic zone. This configuration stimulates P-uptake under anoxic conditions, demonstrates the efficient use of carbon and is instrumental in achieving an annual average effluent Total-P concentration of less than 0.17 mg/l. The phenomenon of denitrification by BioP organisms was included in the Biowin Model developed by Dold (Biowin Manual). This paper describes experiments and full-scale plant observations to establish the role of BioP organisms in the removal of nitrates in the anoxic zone of a plant which also receives a portion of the primary effluent and verification of the Biowin model.

Field measurements of the wind-induced response of a 254 m high free-standing bridge pylon

Abstract The response to wind action of a 254 m high bridge pylon was measured in situ for a period of 7 weeks in the fall of 1995 in Denmark. Simultaneous and continuous measurements of accelerations, wind speed and direction were recorded at the top of the pylon in its free-standing configuration. In that period, the structure faced three major wind storms with 10-min mean wind speeds at the top of the pylon well above 25 m s −1 . The response of the pylon was characterised by vortex-shedding-induced oscillations. This paper presents the main findings of the field measurement campaign including correlation between wind speeds and accelerations, estimates of Strouhal numbers for crosswind and alongwind response and estimates of damping and natural frequencies. Comparisons between full-scale observations and model-scale experiments are also presented.

実測と台風モデルの平均化時間の違いを考慮した台風シミュレーションによる年最大風速の予測手法

In order to evaluate annual maximum wind speeds due to typhoons, a new probabilistic procedure was proposed in which differences in the average time between observations and calculations were considered. Comparing full-scale observations and wind speeds calculated from a typhoon model, it was found that the average time of the calculated wind speeds was much more than 10 minutes, and the calculated wind speeds did not include the small scale variation which was found in the observations. By introducing the probabilistic procedure into the Monte-Carlo technique, the calculated probability distribution for 10 minutes of mean annual maximum wind speed had better agreement with observations than those by the conventional approach which underestimated annual maximum wind speeds.

Stressed state of a rock mass with protective extraction in the wings of tectonic faults

For the October deposit conditions extraction of the gently-sloping deposit of copper-nickel ores within the wings numerous faults intersecting the ore body is connected with increased danger of rock bursts and the requirement for carrying out a considerable amount of labor-consuming driving of dead ends. Mining is carried out in a continuous sequence by layers and chambers with stowing of the worked-out space with consolidating mixtures. Previously by driving and filling parallel cross drifts over the upper contact of the deposit a continuous concrete layer is built. The workings are orientated almost along the strike of tectonics fractures [1]. In seeking the possibility of reducing the volume of driving in zones of tectonic faults industrial experiments were carried out in two areas of the deposit intersected by faults. In contrast to the traditional scheme for constructing a protective slice there was simultaneous erection of sections of a protective slice within the wings of a fault before approaching the extraction front of the main reserves towards the tectonic fault zone. It was assumed that presence of an additional front of a protective slice leads to mutual shifting of the wings of a tectonic fault with loosening of the ore mass. As a result of this treatment of the reserves in the wings of the fault was accomplished without creating a protective slice beneath part of the ore bounded by the overlaying strata. The set of instrument and full-scale observations confirmed this assumption. In test areas both in stopes created beneath the protective slice and in the overworked part of the ore body no signs of increased mine pressure were noted [2]. However, industrial experiments were limited by the specific mining and geological conditions. Observations and measurements made in the test areas give information about the mechanical state of the rock mass at a limited number of points. Transfer of the technology to other conditions and depths requires additional substantiation and studies connected with considerable expenditure and organizational difficulties. In this situation it is possible most simply by means of mathematical modelling to reveal the most common features of stress field formation within the vicinity of a fault. Calculations of the stress-strain state for a rock mass were performed by the finite element method. In the mathematical describing material deformation the rock mass outside the plane of a tectonic fault was represented by elastic materials with corresponding mechanical properties. This assumption is correct in view of the fact that the rocks comprising the rock mass have high elasticity constants and the theological properties appear to an insignificant extent. The deformation of a tectonic fault was described by an elastoplastic material reflecting the main features of fault behavior under load [3, 4]. The original stressed state for the ore and surrounding rock masses is characterized by the presence of tectonic forces. Horizontal compressive stresses are 0.6-1.7"rH, and vertical stresses are 0.6-1.43,H (H is working depth). The most clearly expressed regions of disturbance of the original stressed state are confined to large amplitude faults. According to measured data in them both horizontal and vertical stresses may predominate which may lead to a marked difference in the mechanism of rock mass deformation within the vicinity of a fault on introducing mine working. In the present work the case is considered when within the vicinity of a tectonic fault horizontal stresses predominate. The original stress field in all of the calculations discussed below is adopted as follows: Cry = 3'H, a x = 1.53,H, rxy = 0. Corresponding to this at the outer boundary of the calculation region normal and tangential force components were prescribed. The stress -strained state of the rock mass was determined for the plane strain condition which is fulfilled here due to the considerable extent of a tectonic fault, and stoping and preparatory workings in direction perpendicular to the section in question. Values of mechanical properties for the ore body, the surrounding rocks, and stowing material were taken as typical for the October deposit conditions [5]. The corresponding values of Young's modulus were 5" 104, 8- 104 and 3.104 MPa, and for Poisson's ratio they were 0.25, 0.2, and 0.4. The ore body thickness was 25 m.

Doppler observations with stock meteorological radar

A 10-cm Doppler kit for a stock MRL-5 meteorological radar is described. Signal-processing algorithms and the results of full-scale observations are presented. Coherent operation expands the information-acquisition possibilities of stock meteorological radars.

Calculated and experimental investigations of lateral earth pressure on a block pumphouse of the zaporozh'e nuclear power plant

Results are set forth from a set of investigations (full-scale observations, laboratory experiments, and calculations by the finite-element method) to determine the lateral earth pressure on the underground part of a block pumphouse of the Zaporozh'e nuclear power plant. Laboratory investigations of sandy soils made it possible to confirm the validity of basic premises of a model of nonassociated plasticity and suggest a procedure for determining the model's parameters. Comparison of the results of FEM calculations with data from full-scale observations showed that satisfactory correspondence is achieved only by taking into account strengthening and the sequence of erection of the structure and backfilling.

Physical modeling of water sprays—comparison against field operations

AbstractThis paper discusses the procedure developed for simulating water sprays at a reduced scale (i.e., physical modeling) and, more impotantly, compares the model spray characterstics to corresponding full scale spray characteristics. An ideal physically modeled spray would simulate actual spray momentum, water volume flow rate, air entrainment rate, discharge water pressure, spray angle, spray pattern and drop size distribution. Full scale measurements or estimates of air discharge velocity, momentum, entrainment rate and drop size distributions were obtained for two types of sprays at two discharge pressures, various spray angles and at a 500 gpm flow rate. Physical modeling was conducted to simulate the full scale nozzles at a 1:50 scale reduction using commercially available spray nozzles. Measurements of spray momentum, volume flow rate and air entrainment rate were obtined for a subset of spray angles used in the full scale testing. Particle size distribution was not measured since it was considered of secondary importance in the simulation. The results of the study showed that model and full scale momentum, volume flow rate and air entrainment rates compared well with corresponding full scale observations (i.e., within 10 percent for momentum, 20 percent for volume flow rate and 25 percent for air entrainment rate). The results indicate that the method used for simulating water sprays is valid and that the model sprays adequately simulate the mechanical action of full scale sprays on vapor clouds. The results provide evidence that physical modeling can be used to evaluate the effectiveness of water sprays as a mitigation technique.

Influence of SO 2 on the [formula omitted] chemistry in fluidized bed combustion : 2. Interpretation of full-scale observations based on laboratory experiments

In circulating fluidized bed combustion of coal, significant interactions between desulfurization by limestone and emissions of nitrogen oxides (NO, N 2O) are generally observed. In order to facilitate interpretation of experimental results obtained in a 12 MW circulating fluidized bed boiler, a series of laboratory tests have been carried out. The tests include homogeneous CO and HCN oxidation in the presence of different concentrations of SO 2, CO oxidation catalysed by calcined and partly sulfated limestone particles, and formation and reduction of NO and N 2O over bed material containing char. The presence of SO 2 in the gas is shown to decrease the rate of homogeneous CO and HCN oxidation and thereby change the product distribution of the nitrogen-containing species. Unlike sulfated limestone, calcined limestone (CaO) is shown to be a good catalyst for oxidation of CO. A lower mean CO concentration is therefore expected in fluidized bed combustors during injection of limestone. This indirectly influences the nitrogen chemistry. Finally, the influence of NO and O 2 on the formation of N 2O from char was studied.

Full-scale observations of the condition of structures of the Dneprodzerzhinsk lock

1. According to results of inspections and full-scale monitoring by workers from the scientific research division of the Ukrainian Institute for Designing of Hydrotechnical Construction, and also analysis of all of the data from full-scale observations during the period of the lock's operation, it is noted that safe and reliable operation of the structures is provided by the design and high-quality performance of construction and erection work, and also by the organization of inspection, which includes measures to conduct constant observations of the structure, with observance of the rules of technical operation. 2. Settlements of concrete structures occurred mostly evenly and did not exceed 7.6 mm during the observed period. Relative movements of adjacent sections in the plane of joints did not exceed 3.2 mm; a somewhat larger value of them was noted in sections adjacent to the ends of the lock. The seasonal amplitude of the width of opening of joints was 0.3–6.8 mm. The amplitude of seasonal displacements of the top of the walls with a full chamber is almost two times less than with an empty one. 3. To improve monitoring of the structures' condition, for example, in sections adjacent to the downstream and upstream ends of the lock with mooring, it is recommended that the operating personnel be equipped with elevation and gap-measuring marks, and it is also suggested that they follow the instructions for observations at hydrotechnical structures.

Condition of the rock base and concrete dam of the Krasnoyarsk hydroelectric station

1. Results of full-scale observations of overall displacements of the dam, the behavior of joints between sections, settlements of the rock base, and seepage processes in the dam and its base indicate good technical condition of the structure noted throughout the 20 years of its operation. 2. Indices of the operating structure's condition, on the whole, correspond to design expectations.

Full-scale observations of dam of the Hoabinh hydraulic development during construction period

1. The observations and installed control-measurement instruments on the whole ensured the required control conditions for the rock-earth dam of the Hoabinh hydraulic development and the carrying out of analyses of its state. 2. An analysis of the structure behavior performed using data from instrumental observations showed that the stress-strain conditions of the dam are favorable and correspond to the requirements intended to ensure its reliable operation. The development and distribution of the stress-strain conditions of the dam conform to the design assumptions. Earthquakes in the hydraulic-development region did not affect the process of development of the measurable deformations. 3. The results of observations of the seepage regime of the dam and the base indicate normal operating conditions. The hydraulic gradients on the curtain and the base do not exceed the allowable values. The antifiltration curtain effectiveness is uniform along the front and is stable with time. 4. An analysis of the full-scale observation results performed when construction of the structure was completed showed that the dam body settlements are in the attenuation phase, that the pore pressure dissipation process has been practically completed, and that the parameters of seepage flow in the dam and the base are below the allowable values. The structure state indices permit giving an optimistic prediction of reliability of the dam under rise of the reservoir water elevation to the NPL.

Natural and engineering-geologic conditions of site of rock-earth dam of the Hoabinh hydraulic development

1. The engineering-geologic conditions of the rock-fill dam site after implementation of the technical measures for clearing the river bed and the bank abutments to remove sandy and cohesive soils, correspond to the design requirements placed on the dam base. 2. The individual small sand lenses left in the base of the dam have not affected its stability or seepage characteristics, which is confirmed by full-scale dam observations carried out during seven years.

Iceberg/Seabed Interaction Events Observed During the DIGS Experiment

Abstract The Dynamics of Iceberg Grounding and Scouring (DIGS) experiment was conducted in the Labrador Sea during August 1985. The objectives of the experiment were to obtain full-scale data sets documenting iceberg/seabed interactions, and to obtain by direct observation new information regarding the processes of iceberg scour formation and degradation. Utilizing a vessel and a helicopter, measurements were made of icebergs’ above and below-water shapes, plus local winds, waves, currents and tides. Special self-contained motion monitoring packages were deployed by helicopter on icebergs thought to be good grounding candidates. Seabed observations were made directly using the submersible Pisces IV, and extensive side-scan sonar data were collected. This paper describes two dynamic iceberg/seabed interaction events documented during DIGS: the roll/pitting behavior of the 1.2-million-ton domed iceberg “Bertha,” and the split/grounding behavior of the 7.7-million-ton tabular iceberg “Gladys.” This latter event is particularly interesting due to its very energetic nature, and the fact that it represents the only full-scale observation of any iceberg impact with sufficient documentation to yield estimates of the interaction forces. Subsequent to the experiment, the recorded above and below-water shapes were used to obtain hydrostatic stability maps for these icebergs. A time stepping procedure was also developed to re-create these two dynamic events, and comparisons between the observed and simulated motions are provided in this paper.