School of Civil Engineering Publications - UQ eSpace

A back-trajectory and air mass climatology for the Northern Shenandoah Valley, USA

2012-07-23T00:00:00Z

A bayesian artificial neural network method to characterise laminar defects using dynamic measurements

2007-08-23T00:00:00Z

A case study of water management on closure of an open pit mining operation in North Queensland, Australia

2007-08-24T00:00:00Z

Accurately measuring the abundance of benthic microalgae in spatially variable habitats

2008-02-18T00:00:00Z

Although many studies measure the abundance of benthic microalgae (BMA), at the meters squared scale, comparing these studies is difficult due to the variety of sampling, extraction, and analysis techniques. This difficulty is exacerbated by the fact that BMA abundance has high spatial and temporal variability, at all spatial scales. A suitable standard sampling regimen would reduce variation in estimates due to different sample collection and processing greatly facilitating comparisons between studies. This study examined the effect of varying the volume of extraction solvent, sampling core diameter, and sample replication on BMA biomass estimates. Key findings, applicable to all spatial scales, to accurately determine biomass were the use of a minimum sediment to extraction solvent ratio of 1:2 and use of a sampling core diameter of 19 mm. Across a wide range of sediment types, at the meters squared scale and using spectrophotometric techniques, a minimum replication number of 8 was found to be appropriate. We report the significant effect coring depth and units of expression have on BMA biomass estimates across a range of sediment types, highlighting the potential pitfalls when comparing studies.

A change in flow

Chanson, Hubert — 2009-02-06T00:00:00Z

Acid drainage management and closure design of a sulfidic tailings storage facility in a dry climate

2010-04-28T00:00:00Z

The conventional deposition of potentially acid forming sulfidic mine tailings as a slurry results in seepage, with the potential to contaminate surface and ground waters, particularly during deposition, and possibly post-closure. In a dry climate, tailings deposition can be cycled to largely evaporate excess water, and on closure the tailings may remain desiccated to the extent that incident rainfall will not result in continued acidic drainage and contamination of the surrounding environment. The purpose of any cover would then be to limit dust, promote some vegetation and improve aesthetics, rather than to shed rainfall runoff, which would result in a poor vegetative cover and erosion. To test this hypothesis, a trail tailings cell at a mine in arid Western Australia has been instrumented with moisture and suction sensors located on towers placed prior to tailings deposition. Tailings were deposited over 18 months, and the cycles of desiccation and rewetting were monitored by the in situ instrumentation. This paper describes the life cycle of tailings deposition and desiccation, the moisture and suction data collected during the deposition and desiccation phases, and addresses the potential for long-term acid drainage to occur post-closure and the design of a suitable cover system.

Acid mine drainage and minesite salinity

Williams, David J. — 2007-12-12T00:00:00Z

Acid Mine Drainage and Minesite Stability (Technical Paper 9509)

Williams, David J. — 2004-04-02T00:00:00Z

Acid mine drainage (AMD) and minesite salinity are arguably the most serious threats posed to the environment by open cut mining and mineral processing. AMD arises when sulphur, usually in the form iron sulphide (pyrite) contained in the ore and/or waste materials, is exposed to oxidation, the products of which are leached out as acid. As the pH of the system drops, bacteria begin to catalyse the chemical reaction. Open cut mining and mineral processing also lead to the storage of water on the surface where evaporation raises the salinity of the water. This paper reviews some of the acid mine studies done in recent years, suggests engineered solutions to mitigate the problem and shares some local experiences of AMD and minesite salinity.

A client-server architecture for a real-time traffic information system on the Internet

Dia, H. og Funes, C. — 2010-07-26T00:00:00Z

A closed-form solution for the distortional buckling of I Beams

Ronagh, H. R. og Ng, M. L. og Poon, P. S. — 2007-08-24T00:00:00Z

A comparison of predicted and measured Time - dependent deformations in high strength concrete columns

Dux, P. F. og O'Moore, L. — 2008-06-06T00:00:00Z

A comparison of trajectory and air mass approaches to examine ozone variability

2012-07-23T00:00:00Z

A comparison of two mine waste beach profile equations

Morris, Peter H. og Williams, David J. — 2007-12-12T00:00:00Z

Mine tailings are commonly disposed of in slurry form by subaerial deposition from a pipeline. Coarse mine wastes may be combined with the tailings. At discharge points along the pipeline, the slurry forms sloping beaches whose profiles have a direct bearing on the volume of tailings that can be stored in a given impoundment. The profiles of such beaches are described well by both a power law equation and an exponential equation that incorporate different profile concavity parameters. These two equations, which have been compared previously on the basis of very limited data, are re-examined here on the basis of a much-expanded data set. The exponential equation, which has a theoretical basis, fits the profiles of most beaches slightly better than the empirical power law equation. On average, it gives slightly higher estimates for the volume of tailings that can be stored in a given impoundment. A simple method of conversion from -one profile equation to the other is described.

A conceptual framework for modelling dynamic driver behaviour using intelligent agents

Dia, H. F. — 2008-06-06T00:00:00Z

A conceptual framework for modelling the environment impacts of intelligent transport systems

Dia, H. F. — 2008-06-06T00:00:00Z

A continuum model for infiltration problems

2013-04-03T18:01:19Z

This paper presents an approach for transport and infiltration of a suspension through a porous medium. The aim is to develop a mesoscopic continuum multiphase model, which takes infiltration processes into account. For this purpose, a Representative Volume Element (RVE) is considered and described by the continuum mixture theory extended by the concept of volume fractions (Theory of Porous Media - TPM). The thermodynamical-consistent TPM is a mesoscopical multiphase modelling approach, extended from classical single-phase continuum mechanics. In the present context, we further enhance the concept of volume fractions by certain distribution functions.

A coupled knowledge-based expert system for design of liquid-retaining structures

Chau, K. W. og Albermani, F. — 2007-08-15T00:00:00Z

This paper describes a coupled knowledge-based system (KBS) for the design of liquid-retaining structures, which can handle both the symbolic knowledge processing based on engineering heuristics in the preliminary synthesis stage and the extensive numerical crunching involved in the detailed analysis stage. The prototype system is developed by employing blackboard architecture and a commercial shell VISUAL RULE STUDIO. Its present scope covers design of three types of liquid-retaining structures, namely, a rectangular shape with one compartment, a rectangular shape with two compartments and a circular shape. Through custom-built interactive graphical user interfaces, the user is directed throughout the design process, which includes preliminary design, load specification, model generation, finite element analysis, code compliance checking and member sizing optimization. It is also integrated with various relational databases that provide the system with sectional properties, moment and shear coefficients and final member details. This system can act as a consultant to assist novice designers in the design of liquid-retaining structures with increase in efficiency and optimization of design output and automated record keeping. The design of a typical example of the liquid-retaining structure is also illustrated. (C) 2003 Elsevier B.V All rights reserved.

A coupled model for simulating surface water and groundwater interactions in coastal wetlands

2011-11-13T00:00:00Z

Acoustic Doppler Velocimetry (ADV) in a Small Estuarine System. Field Experience and "Despiking"

2005-09-16T00:00:00Z

Estuarine mixing and dispersion are turbulent processes. Present understanding of estuary turbulence remains however limited, partly because long-duration studies of turbulent properties are difficult and rare. Herein, some long-duration turbulence data recorded at high frequency using acoustic Doppler velocimetry (ADV) are analysed. The data sets were collected in a small sub-tropical estuary. A new ADV data post-processing technique is developed for turbulence analysis of estuarine flows. The results show that acoustic Doppler velocimetry data cannot be used without suitable post-processing. Even classical "despiking" techniques are not simply applicable to natural unsteady estuary flows.

Acoustic Doppler Velocimetry (ADV) In Small Estuary : Field Experience And Signal Post-Processing

2008-08-22T00:00:00Z

Estuarine mixing and dispersion are unsteady turbulent processes. The present understanding of estuary turbulence remains limited because of limited suitable measurement techniques and a lack of long-duration high-frequency studies of turbulent properties. Herein turbulence data were recorded in a small estuary at high-frequency using acoustic Doppler velocimetry (ADV). The data sets were analysed, and the results demonstrated that acoustic Doppler velocimetry data cannot be used without suitable post-processing in unsteady estuary flows. Even classical "despiking" techniques are not simply applicable. A new ADV data post-processing technique is developed herein for turbulence analysis of estuarine flows, and it is tested for several field studies.

Acoustic Doppler Velocimetry (ADV) in the Field and in Laboratory: Practical Experiences

Chanson, Hubert — 2008-11-28T00:00:00Z

In many waterways and estuaries, a basic understanding of turbulent mixing is critical to the knowledge of sediment transport and predictions of contaminant dispersion and water quality. These flows are turbulent and velocity measurements must be conducted at high frequency to resolve the small eddies and the viscous dissipation process. The acoustic Doppler velocimetry (ADV) is designed to record instantaneous velocity components at a single-point with such a relatively high frequency. The ADV signal strength may provide further information on the instantaneous suspended sediment concentration (SSC). Laboratory and field experiences demonstrated that the ADV metrology is a robust technique well-suited to steady and unsteady turbulence measurements in open channel flows. But the ADV outputs must be processed carefully while the calibration of an ADV for SSC measurements is critical. Laboratory and field experiments with turbulence measurements in open channels are discussed herein. Past experiences showed unequivocally that turbulence properties should not be derived from unprocessed ADV signals and that even classical "despiking" methods were not directly applicable to many field and laboratory applications. A successful data analysis relies often upon solid practical experiences with the instrumentation, its capabilities and its limitations.

Advanced materials for energy and environmental applications

X S Zhao — 2012-03-06T00:00:00Z

Advanced measurement methods in time domain reflectometry for soil moisture determination

2011-10-20T00:00:00Z

Advanced Post-Processing and Correlation Analyses in High-Velocity Air-Water Flows

Chanson, Hubert og Carosi, Giovanna — 2007-12-02T00:00:00Z

The interest in air-water flows has not diminished in recent years, but it is accompanied by frequent citations of early, sometimes outdated articles. A basic issue is the inadequate, incomplete interpretation of air-water flow instrumentation by hydraulic engineers and researchers. This article comments on high-velocity air-water flow measurements by means of intrusive phase detection probes. This article focus on the bubbly flow structure of high-velocity air-water flow based upon measurements by means of intrusive phase detection probes. It is shown that some advanced post-processing techniques may yields expanded information on the air-water turbulent flow properties and bubbly flow structures. The outcomes demonstrate simple techniques in high-velocity air-water flow analysis.

Advanced Post-Processing and Correlation Analyses in High-Velocity Air-Water Flows. 1 - Macroscopic Properties

Chanson, Hubert og Carosi, Giovanna — 2006-12-14T00:00:00Z

The interest in air-water flows has not diminished in recent years, but it is accompanied by frequent citations of early, sometimes outdated articles. A basic issue is the inadequate, incomplete interpretation of air-water flow instrumentation by hydraulic engineers and researchers. This two-part article comments on high-velocity air-water flow measurements by means of intrusive phase detection probes. It describes some advanced post-processing techniques that yields expanded information on the air-water turbulent structures. The outcomes demonstrate simple techniques in high-velocity air-water flow analysis. They show also that a research project requires a sound supervision with some generous scholarly input from the supervisor associated with the dedication and energy of the young engineer

Advanced Post-Processing and Correlation Analyses in High-Velocity Air-Water Flows. 2- Microscopic Properties

Chanson, Hubert og Carosi, Giovanna — 2006-12-14T00:00:00Z

The on-going interest in air-water flows is accompanied sometimes by citations of outdated articles and some ignorance of key contributions. A basic issue is the inadequate, incomplete interpretation of air-water flow instrumentation by hydraulic engineers and researchers. This article focus on the bubbly flow structure of high-velocity air-water flow based upon measurements by means of intrusive phase detection probes. It is shown that some advanced post-processing techniques may yield expanded information on the air-water structures and particle clustering.

Advective Diffusion of Air Bubbles in Hydraulic Jumps with Large Froude Numbers: an Experimental Study

Chanson, Hubert — 2009-11-24T00:00:00Z

A hydraulic jump is a rapid transition from a high-velocity open channel flow to a slower fluvial motion. It is commonly experienced in streams and rivers, in industrial channels and during manufacturing processes. Herein new detailed air-water flow characteristics were measured in the developing shear layer of hydraulic jumps with partially-developed inflow. The measurements were conducted in a relatively large-size facility with large Froude numbers (5.1 < Fr1 < 11.2). In the developing shear layer, the distributions of void fractions were modelled by an advective diffusion equation. The experimental data demonstrated a close agreement with the theoretical developments, and the air bubble diffusivity was observed to be independent of the Froude and Reynolds numbers although increasing linearly with the distance from the jump toe. The experimental observations highlighted a strong air entrainment rate as well as some spray and splashing above the roller. The measurements of jump toe fluctuations were close to earlier studies. The new data showed that the jump toe oscillation frequency was equal to the production rate of large-scale vortical structures in the developing shear layer, and the average convection speed of the large coherent structures was in average Vej/V1 = 0.32. The void fraction distributions presented a local maximum in the air-water shear layer and its value decreased quasi-exponentially with increasing distance from the jump toe. The shear zone was also characterised by a maximum in bubble count rate. The depth-averaged void fraction data demonstrated a large amount of entrained air as well as a rapid de-aeration of the jump roller. The velocity profiles followed closely some wall jet equations, and the air-water turbulent properties indicated some increasing turbulence levels with increasing distance from the bed. The bubble chord time distributions exhibited a broad range of entrained bubble chord times spreading over several orders of magnitudes. A detailed analysis of the longitudinal structure of the air and water chords suggested a significant proportion of bubble clustering in the developing shear region, especially immediately downstream of the jump toe. The data showed further that, in the shear layer, there was no preferential bubble chord time in the cluster structures. Overall the study highlighted that the convection of air in the mixing zone was an advective diffusion process, although there was some rapid flow de-aeration for all Froude numbers. The technical report is supported by a digital appendix (Appendix D) containing three movies available at the University of Queensland institutional open access repository UQeSpace {http://espace.library.uq.edu.au/}.

Advective Diffusion of Air Bubbles in Turbulent Water Flows

Chanson, Hubert — 2008-02-03T00:00:00Z

In turbulent free-surface flows, strong interactions between turbulent waters and the atmosphere may lead to some air bubble entrainment. The entrained air is advected within the bulk of the flow and the air-water mixing give a whitish appearance to the flow. Free-surface aeration is commonly observed in Nature, at waterfalls, in mountain rivers and river rapids, and at wave breaking. Man-made self-aeration is also common ranging from artistic fountains to industrial applications and hydraulic structures. This chapter reviews the basic mechanisms of self-aeration in free-surface turbulent flows for a range of turbulent flow conditions. New evidences are presented leading to a better understanding of the advective diffusion of air bubbles. Applications include vertical plunging jets, hydraulic jumps, supercritical open channel flows, and high-velocity water jets. Void fraction distributions may be modelled by some analytical solutions of the advective diffusion equation for air bubbles assuming a quasi-homogenous air-water flow mixture. Theoretical models are developed and the results provide a better characterisation of the complex multiphase flow dynamics. Later the microscopic structure of turbulent bubbly flows is discussed. New developments in metrology and signal processing yield a new level of information on the air-water flow structure and the turbulent eddies advecting the bubbles.

Advective Diffusion of Air Bubbles in Turbulent Water Flows

Chanson, Hubert — 2013-02-26T07:26:30Z

Advice on the response to report (See Additional notes for report title)

Chanson, Hubert — 2009-04-23T00:00:00Z

A dynamic method for determining the soil water characteristic curve for coarse-grained soils

Rassam, D. W. og Williams, D. J. — 2007-12-12T00:00:00Z

The air-entry suction is an extremely important parameter in the water characteristic curve, but is difficult to identify when using conventional static methods such as the pressure plate apparatus. In the dynamic method described herein, instantaneous measurement of matric suction and water content are acquired from a soil specimen undergoing a slow drying cycle with the aid of a tensiometer and a soil moisture probe, respectively. The method offers a quick and reliable way of quantifying the drying soil-water characteristic curve (SWCC) for matric suctions of up to 80 kPa. The large number of data points acquired make it easy to obtain an accurate estimate of the air-entry suction. It is particularly effective for soils ranging from medium sands to sandy silts where a nearly continuous SWCC is provided

Aeration and De-Aeration at Bottom Aeration Devices on Spillways

Chanson, Hubert — 2005-10-19T00:00:00Z

Aeration devices are introduced along chute spillways and at bottom outlets to prevent cavitation damage in high velocity flows. Bottom aerators are characterised by large quantities of air entrained along the jet interfaces but also by a strong de-aeration process near the impact of the water jet with the spillway bottom. In this paper, the aeration and de-aeration occurring respectively in the aeration region and in the impact region are reviewed. A re-analysis of air concentration data obtained on models provides information on the flow characteristics at the end of the impact region. These results enable an accurate initialisation of the downstream flow calculations using the method developed by CHANSON (1989b).

Aeration Due to Breaking Waves

Cummings, Peter D. — 2005-10-18T00:00:00Z

The exchange of mass (gases, water & salts) between the oceans and the atmosphere is vital to the maintenance of life on earth. At high wind velocities most of this exchange is attributable to breaking wave entrained air bubbles. A vertical supported planar plunging jet experiment was used to model the entrainment process. The bubbles were detected with a dual tip conductivity probe and a video camera. At plunging jet velocities below 1.0m/s there is no bubble entrainment. This inception velocity appears to have a Froude and Weber number scaling for large rough turbulent jets. At jet velocities up to 5m/s air appeared to be entrained via intermittent air cavities at the jet - plunge pool intersection. The entrained air packets subsequently break in the two phase free shear layer under the entrainment point. At higher jet velocities there may be partial penetration of the aerated jet surface via pulsating induction cavities plus air entrainment via jet self aeration before impact. Plunging jet air flow data displays the different types of entrainment mechanisms. Mono-phase diffusion models can be successfully adapted to describe the shear layer developing zone. The diffusion of the air bubbles is approximately a Gaussian self similar process. The mean bubble velocity profiles can be modelled using the Goertler Error function or Hyperbolic Tangent models. The bubble spectra is approximately Lognormal with a geometric mean diameter of 1.0-2.0mm for a range of jet velocities. A bubble Weber number is found to model the maximum bubble size of approximately 10mm diameter. An original adaptation of the potential flow solution for the vortex sheet is shown to be a simple and reasonably accurate finite amplitude model for water surface gravity waves, especially in deep water. This model has some interesting features, such as both vertical and horizontal asymmetry and standing wave water profile modelling. A simple and possibly insightful model of wave growth due to the wind is introduced, using a constant sea surface Reynolds number U*.sqrt(LF)/Gamma, where U* = wind friction velocity, L = wavelength, F = fetch, and Gamma = wave field vortex circulation per wavelength. The results may have application in the modelling of air - sea gas exchanges, predicting breaking wave forces on structures and the use of the planar plunging jet as an aeration device in industry.

Aeration for plant root respiration in a tidal marsh

Li, H. L. og Li, L. og Lockington, D. A. — 2007-08-15T00:00:00Z

This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. ( 2004) by using a two-phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single-phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass ( TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two-phase model and predicted TAAM flux magnitude, provide further insight into the positive feedback'' mechanism proposed by Ursino et al. ( 2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.

Aeration of a Free Jet Above a Spillway

Chanson, Hubert — 2005-09-02T00:00:00Z

A study of air entrainment above an spillway aerator is presented and discussed with a dimensional analysis. We conclude that similitude of air entrainment processes for spillway aerator is not possible between model and prototype. New informations on the aeration region are presented and an analytical solution of the upper nappe entrainment is developed.

Aeration of the Ocean due to Plunging Breaking Waves

Chanson, Hubert og Cummings, Peter D. — 2005-10-25T00:00:00Z

The aeration of the ocean is an important factor contributing to the transfer of oxygen, nitrogen and carbon di-oxide between the ocean and the atmosphere. Breaking waves are known to enhance the aeration process by increasing the turbulent mixing and entraining air bubbles. One type of breaking waves, the deep sea plunging breaker, can entrain large quantities of air bubbles at depth as large as 10 to 20 metres. The resulting increase of air-water interface area and the increase of gas saturation distribution with the pressure induce a massive augmentation of air-water transfer of atmospheric gases. An attempt to estimate the characteristics of plunging breaking waves is developed using a similarity with plunging jets. The results are consistent with experimental observations and emphasise the role of deep sea plunging breakers in the aeration process. Further they provide a method to estimate the gas transfer rate due to plunging breaking waves.

Aeration performance of low drop weirs - Discussion

Chanson, H. — 2007-08-13T00:00:00Z

Aerodynamic measurements: from physical principles to turnkey instrumentation

Chanson, Hubert — 2013-03-18T11:21:45Z

A Field Investigation into the Groundwater Dynamics of Raine Island

2008-03-03T00:00:00Z

Raine Island is the nesting site for the world’s largest remaining population of the green turtle (Chelonia mydas) and the most significant seabird rookery in the Great Barrier Reef World Heritage Area. Surveys of turtle nesting conducted by the Queensland Parks and Wildlife Service have indicated that the nesting success rate may be reduced due to flooding of the nests by groundwater. An expedition to the island in November-December 2006 was undertaken to investigate the beach groundwater dynamics. The field data was analysed and used to develop a simple mathematical model of the watertable response to tidal oscillations. The groundwater data was combined with sand surface survey data to enable the estimation of the depth of sand available for green turtle nesting above the high tide inundation level.

A field study on groundwater dynamics in a salt marsh - Chongming Dongtan wetland

2012-04-09T12:02:18Z

Subsurface hydrology plays an important role in governing the behaviour of salt marshes, in particular, nutrient exchange, plant zonation and carbon cycling. The objective of this paper is to examine the hydrological characteristics of a salt marsh based on a field investigation conducted at a cross-creek section in the Chongming Dongtan wetland (Shanghai, China). Field measurements showed complex groundwater table fluctuations, controlled by multiple factors. The groundwater table near the creek responded quickly to the creek water level fluctuation, in contrast with the weak water table response in the marsh interior. The average elevation of the groundwater table near the creek was lower than that in the interior, suggesting that the optimal soil aeration condition occurred near the creek. The variations of pore water salinity along the cross-creek transect also appeared to be complex even though a low salinity zone remained present near the creek levee over the investigation period. Relatively strong pore water circulation near the creek prevented local solute accumulation. These results are essentially consistent with the hypothesis that the area near the creek is better suited for plant growth. In the marsh interior, weakened drainage and flushing effects may leave the soil largely saturated for a long period and suppress carbon exchange between the marsh soil and ambient environments (coastal water and atmosphere).

A finite mixing length theory for turbulent diffusion

Nielsen, Peter og Teakle, Ian A. L. — 2009-02-03T00:00:00Z

A finite-mixing-length theory is presented for turbulent mixing. This theory contains Fickian diffusion as the limiting case for lm/L-->0, where lm is the mixing length and L is the scale of the distribution under consideration. The new model is of similar generality to that of Taylor (1921), "Diffusion by continuous movements." However, while Taylor's model, being strictly Lagrangian, is difficult to apply to inhomogeneous scenarios, the new model is Eulerian and easily applicable to bottom boundary layers and other inhomogeneous flows. When applied to steady suspended sediment concentrations c(z), the theory predicts the observed trend of apparent Fickian diffusivities epsilonFick = –wsc/(dc/dz) being larger for particles with larger settling velocity ws, in a given flow.

A framework for evaluating the costs and benefits of e-business in the railway industry

Tetther, C. og Ferreira, L. — 2009-11-26T00:00:00Z

A framework for infrastructure sustainability assessment

2012-09-25T10:07:28Z

A Fundamental Study of Turbulence and Turbulent Mixing in a Small Subtropical Estuary

Trevethan, Mark — 2008-03-04T00:00:00Z

The flow of water in natural systems such as estuaries is a turbulent process, with Reynolds numbers greater than 1E+5. Understanding the turbulence properties of an estuary is important for the investigation of mixing, dispersion and sediment transport within an estuary. This study investigates the turbulence properties in a typical small subtropical estuary (Eprapah Creek, Australia). Small coastal plain type estuaries constitute approximately 60 % of all estuaries in Australia, yet no thorough study of the turbulence properties of this type of estuary has been conducted. To date only a limited number of turbulence studies in estuaries have been undertaken. One reason for this was the lack of appropriate instrumentation to collect turbulent velocity measurements with fine spatial and temporal resolutions. This is especially true of turbulence studies in small estuaries, with the majority of published turbulence studies being performed in relatively large systems. Previous studies of turbulence in estuaries were mostly conducted for relatively short periods (up to 6 hours) and by collecting data over long periods in bursts of several minutes. The present study showed that acoustic Doppler velocimetry (ADV) was well suited for the measurement of turbulence properties in small estuarine systems. A unique aspect of this study was the continuous collection of turbulence data at high frequency (fscane ≥ 25 Hz) for relatively long periods (Tstudy up to 50 hours). This approach characterised the estuarine turbulence properties for up to two complete tidal cycles. The data analysis showed that continuous collection of high frequency turbulence data was essential to accurately characterise the rapid fluctuations of turbulence in an estuary. The field data showed that the turbulence flow properties were highly fluctuating in a small estuary. All turbulence properties exhibited large and rapid fluctuations over the investigation period of each field study. The variations in time scales were related to both the instantaneous local flow properties and the tidal fluctuations. Some long period oscillations observed in the water level and velocity data also had a significant impact on the turbulence properties. These long period oscillations had periods similar to resonance periods generated both internally in and externally to the creek. Many turbulence properties showed an asymmetrical response to the tidal forcing, especially under spring tidal conditions. Large turbulent velocity fluctuations were, however, observed throughout all investigation periods, including during the slack tides. Substantial fluctuations in the normal and tangential Reynolds stresses were observed in the middle and upper estuarine zones. The turbulent velocity data showed some non-Gaussian behaviour and the Reynolds stresses were non-Gaussian throughout all investigation periods. Field data collected mid estuary under spring and neap tidal conditions showed two distinctly different turbulence responses for spring and neap tides. During spring tides, the magnitudes of all turbulence properties were up to an order of magnitude larger than for neap tides. The turbulence properties showed some increased tidal asymmetries under spring tidal conditions. Further two field studies were conducted under similar neap tidal conditions in the middle and upper estuarine zones. A comparison of these two data sets showed that the turbulence properties in the middle and upper estuaries differed substantially. Mid estuary, the magnitude of the turbulence properties were up to an order of magnitude larger than those observed in the upper estuary, thereby indicating that at least three distinct sets of turbulence properties existed in this small subtropical estuary. This study included some turbulence data collected in a large tidal lake with a restricted entrance (Hamana Lake, Japan). This turbulence data was compared with the data measured in Eprapah Creek. The comparison showed similar tidal patterns in some turbulence properties were observed close to the bed despite the distinct topography and hydrodynamics of the two estuaries. Some of these patterns in turbulence properties were also observed in previous studies of turbulence in estuaries. However, the spring tide data collected in the small estuary showed an increased magnitude of turbulence and a more asymmetrical response than other estuarine turbulence studies. The ratio of local tidal amplitude and local mean depth was used to characterise the local turbulence properties for a certain tidal range. A critical value of the ratio a1/h1 was 0.5, corresponding to the local tidal range being equal to the local mean depth. If the tidal range was greater than the local mean depth (i.e. a1/h1 > 0.5), a more asymmetrical tidal response and some increased turbulence property magnitudes were observed. A comparison of the turbulence properties in two distinct tidal systems (Eprapah Creek and Hamana Lake) showed similar tidal patterns for a1/h1 < 0.5.

A fuzzy method for predicting the demand for rail freight transportation

Wong, WG og Niu, H og Ferreira, L — 2009-11-16T00:00:00Z

The demand for rail freight transportation is a continuously changing process over space and time and is affected by many quantitative and qualitative factors. In order to develop a more rational transport planning process to be followed by railway organizations, there is a need to accurately forecast freight demand under a dynamic and uncertain environment.. In conventional linear regression analysis, the deviations between the observed and the estimated values are supposed to be due to observation errors. In this paper, taking a different perspective, these deviations are regarded as the fuzziness of the system’s structure. The details of fuzzy linear regression method are put forward and discussed in the paper. Based on an analyzes of the characteristics of the rail transportation problem, the proposed model was successfully applied to a real example from China. The results of that application are also presented here.

A fuzzy neural approach to modelling behavioural rules in agent-based route choice models

Panwai, S. og Dia, H F — 2007-08-23T00:00:00Z

A General Correlation for Turbulent Velocity Profiles of Dilute Polymer Solutions

Chanson, Hubert — 2005-10-20T00:00:00Z

The writer would like to congratulate the authors for their complete and comprehensive study of turbulent velocity profiles of dilute polymer solutions. He wish to draw their attention to the similarity between the mechanisms of drag reduction due to the injection of polymers and the reduction of friction factor due to air entrainment in high velocity open channel flows.

Agent applications in rail transportation

Ho, T. K. og Ferreira, L. — 2009-11-26T00:00:00Z

This paper discusses the applications of agent-oriented techniques for modelling of the behaviour of a railway transportation system which consists of numerous interacting parties with different objectives, interests, autonomy, constraints, responsibilities and decision-making capabilities. The agent model covers both business and operational aspects of the system and it enables possible connections to other modes of transportation and/or external monitoring bodies. The multi-agent architecture required to match a real-world railway system will be presented and the additional functions and advantages brought by the agent model will also be explored.

A Heuristic Approach to Optimise Public Transport Priority in an Urban Network

Mesbah, Mahmoud og Sarvi, M. — 2011-10-19T00:00:00Z

A high-resolution method for the depth-integrated solute transport equation based on an unstructured mesh

2013-03-03T00:56:46Z

This paper presents a high-resolution numerical method for solving mass transport problems involving advection and anisotropic diffusion in shallow water based on unstructured mesh. An alternating operator-splitting technique is adopted to advance the numerical solution with advection and diffusion terms solved separately in two steps. By introducing a new r-factor into the Total Variation Diminishing (TVD) limiter, an improved finite-volume method is developed to solve the advection term with significant reduction of numerical diffusion and oscillation errors. In addition, a coordinate transformation is introduced to simplify the diffusion term with the Green-Gauss theorem used to deal with the anisotropic effect based on unstructured mesh. The new scheme is validated against three benchmark cases with separated and combined advection and diffusion transport processes involved. Results show that the scheme performs better than existing methods in predicting the advective transport, particularly when a sharp concentration front is in presence. The model also provides a sound solution for the anisotropic diffusion phenomenon. Anisotropic diffusion has been largely neglected by existing flow models based on unstructured mesh, which usually treat the diffusion process as being isotropic for simplicity. Based on the flow field provided by the ELCIRC model, the developed transport model was successfully applied to simulate the transport of a hypothetical conservative tracer in a bay under the influence of tides.