Papers by Roger A Falconer
Proceedings of the Institution of Civil Engineers - Water Management, 2012
Large-scale prototype experiments of regulating flow and sediment have been conducted annually in... more Large-scale prototype experiments of regulating flow and sediment have been conducted annually in the Yellow River, China since 2002, with large amounts of observed hydrological data being collected during the experiments. In the present study, a two-dimensional hydrodynamic model based on the finite-volume method has been refined, with an improvement being made in the spatial reconstruction method of the state variables. The enhanced spatial reconstruction method can account for the effect of a wet or dry interface on the calculation of numerical fluxes, especially for low discharges, which can avoid the occurrence of unreal flow fluxes. The refined model was applied to simulate flood routing in the 2004 and 2006 experiments in the lower Yellow River and relatively close agreement between the model predictions and observed data was obtained. The effect of different bed roughness values on the predicted results was investigated using a sensitivity test, and various factors influenci...
Ocean Modelling, 2010
The Severn Estuary, located in the UK between south east Wales and south west England, is an idea... more The Severn Estuary, located in the UK between south east Wales and south west England, is an ideal site for tidal renewable energy projects, since this estuary has the third highest tidal range in the world, with a spring tidal range approaching 14m. The UK Government recently invited proposals for tidal renewable energy projects from the estuary and many proposals were submitted for consideration. Among the proposals submitted and subsequently shortlisted were: the Cardiff–Weston Barrage, the Fleming Lagoon and the ...
International Journal of River Basin Management, 2012
Floodwater flows through urban floodplains with storm water systems are often inadequate during e... more Floodwater flows through urban floodplains with storm water systems are often inadequate during extreme storm events and/ or when the river flood inundation extent becomes extreme. Such flows may cause potential hazard risks to humans and their properties along the floodplains. Recently, flood hazards relating to vehicles have become more noticeable and it is vital to investigate the hydraulic behaviour
... Junqiang Xia1,2, Binliang Lin1, Roger A. Falconer1 and Guangqian Wang2 1 Hydro-environmental ... more ... Junqiang Xia1,2, Binliang Lin1, Roger A. Falconer1 and Guangqian Wang2 1 Hydro-environmental Research Centre, School of Engineering, Cardiff University, CF24 3AA, UK; Email: [email protected] 2 State Key Laboratory of Hydroscience and Engineering, Tsinghua University ...
Journal of Geophysical Research, 2011
The assimilative capacities of estuaries and coastal seas for effluent discharges are predominant... more The assimilative capacities of estuaries and coastal seas for effluent discharges are predominantly determined by the rates at which pollutant-bearing effluents are first dispersed and then flushed from the coastal region into the open ocean. The dispersion coefficients and flushing, as measured by the water residence time in the Persian Gulf (Arabian Gulf), were investigated using the three-dimensional numerical model Estuary, Lake and Coastal Ocean Model (ELCOM). The model was first validated using the R/V Mt. Mitchell expedition profile data, collected from 27 January to 26 February 1992 and from 13 May to 12 June 1992. The validated model was then used to compute the geographic variability of the horizontal dispersion coefficients K x throughout the gulf. Model results revealed that dispersion was principally driven by the shear associated with the tides, but along the Arabian coast, wind was an additional significant energy source for dispersion. The water residence time was found to be more than 3 years along the Arabian coast, but shorter along the Iranian coast.
Environmental Modelling & Software, 2011
Details are given herein of the refinement and application of a two-dimensional depth integrated ... more Details are given herein of the refinement and application of a two-dimensional depth integrated numerical model to predict geo-morphological changes in tidal basins. An Alternating Direction Implicit finite difference algorithm has been used for solving the governing differential equations, which consist of the conservation of mass and momentum for the hydrodynamics, the transport equation for suspended sediment fluxes and the sediment mass conservation equation for bed level changes. The model includes several criteria for the initiation of motion (i.e. Shields (1936), Kolahdoozan (1999) and Zanke (2003)). As the flow is highly turbulent, and its components have a random nature, many researchers have tried to express the sediment transport processes by using stochastic approaches. In the current study, both deterministic and stochastic methods were included in the numerical model to show their accuracy and efficiency. To evaluate the numerical model results laboratory measurements...
Water, 2015
Details are given in the paper of the refinement of a three-dimensional layer integrated turbulen... more Details are given in the paper of the refinement of a three-dimensional layer integrated turbulence model and its application to a scaled physical model of a reservoir, named Hamidieh Reservoir, in Iran. The strong turbulent flows generated in this reservoir are due to the high volumes of flow diversion, with low head differences. In this paper, a refined numerical model is applied to a reservoir, associated with a dam, water intakes and sluice gates, with the aim being to investigate the flow patterns and sediment transport processes in the vicinity of such hydraulic structures. The calibration of the model is undertaken using measurements made from a scaled physical model. The numerical model is able to predict the conditions for a range of scenarios that are difficult to test in the physical model. Different scenarios are introduced to investigate the effects of various intake and sluice gate configurations, as well as their operation schemes on the flow and sediment transport processes into Hamidieh Reservoir. The results indicate that the flow velocity field in the vicinity of one of the intakes varies significantly. Moreover, the sluice gates do not appear to have any considerable effect on the suspended sediment concentrations moving through the intakes.
Water, 2015
Due to the increasing economic and cultural value of bathing waters and the shellfish industry in... more Due to the increasing economic and cultural value of bathing waters and the shellfish industry in the UK and worldwide, water quality in estuarine and coastal waters has attracted considerable public attention in recent years. To obtain accurate predictions of the concentration distributions of faecal indicator organisms (FIOs) in coastal waters for better management of bathing water compliance, it is necessary to build an integrated modelling system to predict the complete diffuse and point source inputs from river and catchment basins. In the present paper, details are given of the development of such an integrated modelling system for simulating the transport and decay processes of FIOs, from catchment areas upstream from the coastal region, in which a distributed catchment module, a 1D river network module and a 2D estuarine and coastal module are linked dynamically by boundary inputs and outputs. Extensive measured data from the catchments, river networks and estuaries have been collated to determine the model parameters. Verification results of the distribution of water levels, flows and velocities, and suspended sediment and Escherichia coli concentrations, at controlled monitoring sites are presented, which show that the integrated model predictions generally agree well with the measurements, although locally appreciable errors can occur. The model results also highlight the importance of including the flux of FIOs via sediments being an important factor in terms of assessing the quality of bathing waters. The main factors influencing the relatively high concentration values in the bathing region are analysed, based on the model predictions and measured data, with four categories of FIO concentration levels being reviewed.
Natural Hazards, 2015
Flood risk assessment is generally studied using flood simulation models; however, flood risk man... more Flood risk assessment is generally studied using flood simulation models; however, flood risk managers often simplify the computational process; this is called a ''simplification strategy''. This study investigates the appropriateness of the ''simplification strategy'' when used as a flood risk assessment tool for areas prone to flash flooding. The 2004 Boscastle, UK, flash flood was selected as a case study. Three different model structures were considered in this study, including: (1) a shock-capturing model, (2) a regular ADI-type flood model and (3) a diffusion wave model, i.e. a zero-inertia approach. The key findings from this paper strongly suggest that applying the ''simplification strategy'' is only appropriate for flood simulations with a mild slope and over relatively smooth terrains, whereas in areas susceptible to flash flooding (i.e. steep catchments), following this strategy can lead to significantly erroneous predictions of the main parameters-particularly the peak water levels and the inundation extent. For flood risk assessment of urban areas, where the emergence of flash flooding is possible, it is shown to be necessary to incorporate shockcapturing algorithms in the solution procedure, since these algorithms prevent the formation of spurious oscillations and provide a more realistic simulation of the flood levels. Keywords Flash floods Á Natural hazards Á MacCormack scheme Á Total variation diminishing (TVD) Á Shock-capturing Á Boscastle flood Á Flood modelling Á DIVAST
Journal of Hydro-environment Research, 2015
The turbulent structure of open-channel flows over two-dimensional dunes is investigated numerica... more The turbulent structure of open-channel flows over two-dimensional dunes is investigated numerically using large-eddy simulation (LES), in order to improve our understanding of the interaction between the dune-generated turbulence and the free surface dynamics. The filtered NaviereStokes equations in the LES model have been discretised using the finite volume method, with a dynamic sub-grid model being employed for the unresolved scales of turbulence. The partial cell treatment has been implemented in a Cartesian grid form to deal with the dune topography. Both the volume of fluid method and rigid lid approach have been employed in the numerical framework to investigate the effects of the free surface treatment on the flow characteristics. The numerical model predicted mean flow velocities, turbulence intensities and Reynolds stresses have been compared with experimental measurements published in the literature, with a detailed analysis being undertaken to assess the accuracy of the model results and the effects of the free surface treatment on the velocity and turbulence predictions. The instantaneous flow structure has been investigated, with emphasis being focused on the free surface dynamics and coherent structures.
Journal of Hydro-environment Research, 2015
ABSTRACT The hydrodynamics and mixing processes in small- and full-scale baffled disinfection tan... more ABSTRACT The hydrodynamics and mixing processes in small- and full-scale baffled disinfection tanks are studied experimentally and numerically. Velocity and tracer transport measurements are carried out to quantify the hydrodynamics and to obtain reliable data used to validate a three-dimensional computational fluid dynamics (CFD) model. The flow in the tank under investigation is extensively three-dimensional due to the existing inlet condition of the tank, resulting in short-circuiting and internal recirculation, particularly in the first three compartments. Near the inlet the tracer residence time distribution curve analysis and Hydraulic Efficiency Indicators (HEIs) suggest poor disinfection performance. Further away from the inlet, the flow recovers to a two-dimensional flow and the HEIs improve until the exit of the tank. The computational results demonstrate good agreement between the predicted hydrodynamics and tracer transport with the corresponding experimental data. The numerical model is then employed to investigate the effects of up-scaling of laboratory model findings to a full-scale contact tank. Despite the Froude-Reynolds conflict the full-scale contact tank exhibits similar behaviour to the small-scale tank. The effect of the tank geometry on the disinfection efficiency is demonstrated, highlighting the negative impact of flow three-dimensionality on pathogen inactivation.
This paper reviews the traditional approach of linking models to cover integrated water managemen... more This paper reviews the traditional approach of linking models to cover integrated water management from the upper reaches of catchments through river basins, into estuaries and then into the marine environment. It highlights some of the deficiencies in the approaches currently being adopted in many of non-integrated studies, where artificial boundaries are included in the system and then highlights the need for a more integrated conceptual approach. Two example studies are discussed, namely the non-compliance of bathing waters along a UK coastal site from riverine inputs, with the inputs arising from agricultural and urban runoff, and the proposed Severn barrage project where a large barrage is proposed across the Severn estuary to provide 5% of the UK's electricity needs. In this latter case study the barrage will have a major impact on the turbidity levels upstream, which will significantly impact on the levels of light penetration through the water column and potentially faecal indicator organisms. An integrated approach shows that the lower turbidity levels leads to improved water quality, through increased light penetration.
Water Research, 2012
schemes vis-à-vis CFD model complexity vis-à-vis costebenefit ratio of simulations and the inclus... more schemes vis-à-vis CFD model complexity vis-à-vis costebenefit ratio of simulations and the inclusion of state of the art chlorination kinetics and DBP formation modelling in the CFD tools that can assist modern design and retrofit studies of CCTs.
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2010
Tidal stream systems make use of the kinetic energy of tidal movement to power turbines, in a sim... more Tidal stream systems make use of the kinetic energy of tidal movement to power turbines, in a similar manner to the way in which windmills extract energy from the wind. This method of renewable energy generation is gaining in popularity because of the high predictability of tides, the lower investment needed for tidal turbines, and the lower ecological impact, as compared with other schemes involving barrages or lagoons. It is generally considered that a mean spring peak tidal current of at least 2 m/s is required for tidal stream power to be worth exploiting. In the Severn Estuary, the peak tidal current exceeds 2 m/s, with a corresponding minimum depth of greater than 20 m, and it is thereby a potential location for tidal stream power. Previous studies cannot provide the detailed and precise distribution of tidal stream power in this estuary, and it has therefore been deemed appropriate to undertake a numerical model assessment of tidal stream energy resources in the Severn Estuar...
Uploads
Papers by Roger A Falconer