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Modelling fully coupled fluid structure interaction using the computational toolkit Proteus
No full textWith the advance of computer technology and the increasing availability of high performance computing systems, the application of computational fluid dynamics (CFD) models to real life engineering scenarios is becoming increasingly common. These numerical models typically solve the Navier-Stokes equations to simulate complex fluid processes without simplifying assumptions (e.g. 1D flow or depth integration). Clarification is sometime required on when such models provide practical insights and meaningful answers for a range of design problems associated with hydraulic and coastal structures for cost (time and expense) efficiencies.
Recently, there has been an effort among the CFD development community to make these tools available to researchers and engineers through open-source platforms. These platforms contributed in decreasing the cost and increasing the flexibility of CFD models and enabled researchers and engineers working in coastal / hydraulic engineering consultancy industry to use them for addressing engineering applications.
In this work, we present a relatively new open-source model, Proteus. This model aims to model complex processes which are key to reducing uncertainties in the design of hydraulic, coastal and offshore structures. These uncertainties include fully coupled wave-structure interaction, scour and sedimentation and multibody dynamics. The Proteus project was originally initiated as a platform for the numerical solution of the transport equations using the finite element method (FEM), along with a Python interface. The model is currently undergoing a rapid development phase, aiming not only to be sufficiently user-friendly but also efficient enough to be used by the general engineering community.
In this work, we will briefly present the numerical methodology and then focus on presenting a portfolio of relevant case studies and validation cases including wave interaction with fixed and moving structures, including breakwaters and pipelines, modelling of moored and free floating bodies and validation results from the recent development of the sediment transport module
Dredging the Hugli Estuary: creative solutions through client, consultant and contractor engagement
No full textEstablished maintenance dredging practices in ports and harbours are not always optimal, and improvements can often be made to enhance both the economic and the environmental management of a port authority. This paper describes a recent example where both economic and environmental improvements were achieved.
Kolkata Port has been in operation for over two centuries, with the Haldia Dock Complex being operational for almost 40 years. During this period, maintenance of the approach to the ports has been an ongoing concern and this region has the largest maintenance dredging burden of all Indian ports.
HR Wallingford was initially commissioned by WAPCOS Ltd (A Government of India Undertaking) in August 2012 to provide an ‘Expert Third Party Opinion on River Regulatory Measures’ on the Hugli Estuary. A review was undertaken which identified short-term improvement measures. The drivers for the subsequent project (and the focus of this paper) were to improve the efficiency of the maintenance dredging works, reduce dredging costs, and provide increased channel depth. The novel short-term solution identified successfully achieved this and allowed a drastic increase in dredging efficiency. Moreover, the change in methodology allowed significant environmental improvements to be made: carbon dioxide emissions were significantly reduced due to reduced sailing distances, and sediment was better kept within the sediment transport system with a major reduction in offshore placement. Turbidity was increased as a consequence of the short-term solution used, but this was in an environment already characterised by high natural turbidities and subject to anthropogenic changes.
This paper describes the substantial challenges addressed by the project, the novel solution that was identified, trialled and implemented by the project team (including observations from site visits), and the search for a win-win solution
The benefits of simulator based training at Port Hedland
No full textOver the past 25 years HR Wallingford has been developing bespoke simulator based training courses to support harbour authorities in providing continuous professional development (CPD) for Marine Pilots and Tug Masters. This has a particular emphasis on developing best practice, emergency procedures and non-technical skills. During this period the marine industry has undergone a number of significant changes. Vessel sizes have increased significantly with 400m long container vessels, the “Wozmax” bulk carrier and QMax LNG carriers, amongst others. Tug capabilities have also changed rapidly, with higher capacity harbour tugs, of between 60 and 100 tonnes bollard pull, or more. The use of tugs has also changed markedly with new techniques such as bow to bow operations, indirect towing and render recover winches, along with the introduction of Azimuthing Stern Drive (ASD) and more recently Rotor Tug designs. These changes combined with increasing commercial pressures has made ship simulation an essential part of ensuring the safety of vessels within port limits.
HR Wallingford provide ship simulation and CPD training services to the Pilbara Ports Authority, who operate Port Hedland, which is the world’s largest bulk export port, exporting 460,408,649 tonnes in 2015/16. Port Hedland is in the process of managing many of the issues described above. A case study of the training provided and the benefits of ship simulation, along with lessons learnt, will be presented. In particular the benefits of accurate ship hydrodynamic models for close quarters manoeuvring, the inclusion of the full manoeuvring team from Pilot to Tug Master and VTS operator, as well as the assessment of non-technical skills (such as cooperation, communication, decision making, conflict and error management) will be addressed
Developments in property resistance and resilience
No full textWith around three million properties in England affected by severe weather-driven surface water (pluvial) flooding, and the number likely to increase as a result of climate change, it is important that homeowners and businesses are encouraged to take steps to minimise the effects of future flood events. This is where property-level protection and building resilience measures are important. A government guidance document was developed in 2007, based on laboratory and other studies, giving advice on resilient approaches for new buildings. This was adopted by many organisations, particularly to deal with residual flood risks, which cannot always be designed out. Although unsuitable development has been discouraged in areas at high flood risk, with the increased awareness of the need to deal with surface water for existing housing stock, a new, definitive standard was needed. Therefore the British Standards Institution, with the support of Government, has developed a new standard (BS 85500) that updates and extends the earlier guidance document, including retrofitting flood resistance and resilience measures to existing properties.
Developments in property-level protection also continue, and a BSI drafting group is being set up to turn the current PAS 1188 into a full Standard. This is due to start in March 2017 and will also link to issues of certification for the installation of flood products, as well as the professional requirements for flood surveys which inform the most appropriate resistance and resilience measures. This presentation outlines the contents and issues associated with both standards
UK SuDS and Chinese Sponge Cities: solving the problems of urban flood risk management?
No full textThe urbanisation rate in China is higher than anywhere in the world. More than 40,000km2 of land has been developed over the last 35 years, with the number of cities increasing from 193 to 653 and urban populations rising from 170 to 750 million. The Chinese acknowledge that their cities have grown too large, too fast, without adequate planning and environmental risk management. A key outcome is that flooding has become an urgent issue: annually more than 100 cities are affected by floods, and in 2013 234 were flooded. In 2014, direct economic losses from flooding were estimated as RMB157.4 billion (£17.3 billion). Their aim to settle an additional 100 million migrant workers in cities over the next 5 years combined with likely climate change impacts on rainfall mean the stakes in China are high and the drivers for implementing solutions are imperative. Three years ago the Chinese President announced that new cities and redevelopment would conform to a ‘sponge-city’ paradigm and China’s state council announced a new set of urbanisation guidelines.
This paper will describe the Chinese objectives and standards for surface water management, the progress they have made, and the policies required to facilitate the creation of Sponge Cities. It will contrast the Chinese requirements with those in the UK in the context of their potential for mitigating flood risk to urban environments, and the design tools and approaches being adopted to evaluate system performance - referencing pilot projects in which HR Wallingford have been involved
History of Alderney and Jersey "harbours of refuge" – why did they fail?
No full textDuring the early 1800s, Britain still feared the 'Napoleonic threat' from the French Navy and their allies. That fear was used by Parliament to justify the construction of various coastal and harbour schemes, activities in which ICE members were actively engaged. The more explicit threat from France abated with the defeat of Bonaparte's armies at Waterloo in 1815, and his death in 1821 on St Helena, but the momentum of some schemes continued, and fears of a French resurgence fuelled proposals for 'harbours of refuge'. In the Channel Islands, the most notable such harbours were those at Braye Bay, Alderney; and St Catherine's, Jersey. Construction of the breakwaters to form both of these harbours started in 1847. The breakwater at St Catherine's was complete in 1856. The Alderney breakwater was complete to its originally intended length by 1871, but was thereafter abandoned to part length.
This paper will discuss the 'official' reasons given for constructing 'harbours of refuge', and will point to some of the real reasons. It will discuss the two Channel Island sites, and the design and construction of the (three) main breakwaters.
Both harbours failed in different ways. The original 'client needs' were significantly modified or their requirements simply disappeared. The paper will outline how and why these harbours / breakwaters failed, whether they were ever viable
Operational decision support system for sustainable water resource management for Sungai Selangor
Get PDFThe Selangor River lies on the west coast of Peninsular Malaysia, 70 km north of Kuala Lumpur. The Selangor catchment area is approximately 2000 km2 and has two major dams located in the upstream part of the catchment: Sungai Selangor Dam and Sungai Tinggi Dam. Lembaga Urus Air Selangor (LUAS) is the Malaysian government agency responsible for water resources management of the Selangor catchment, their main challenge being to balance an increase in water demand, whilst trying to manage the catchment’s environmental state. Key to this is the amount of water that is being released from the two reservoirs. The current manual decision-making process (based on staff experience) does not provide LUAS with the efficiency and accuracy that is required in a catchment where sustainability is key and water resources are not always abundant. A solution was required to improve the management of the current resources, thus reducing the need for the costly and environmentally contentious development of new infrastructure. The operational Decision Support System (DSS) for sustainable water resources management of the Sungai Selangor catchment is a non-structural tool developed to support LUAS in optimising the reservoir releases and water abstractions in the catchment; it is also known as LUAS Intelligent Support System (LiSS). LiSS is a fully automated system that is driven by a combination of live, telemetered gauged data from various sources including the InfoBanjir telemetry database and Numerical Weather Prediction (NWP) rainfall forecasts from the Malaysian Meteorological Department (MMD). Simulations are carried out automatically on an hourly basis, to calculate and forecast whether flows at Bestari Jaya Barrage near the main abstraction location (SSP1) are being maintained at the required levels. If the required flows are not met, being either too high or too low, the model is re-run using an adjusted reservoir release time series. LiSS should also be able to help LUAS in future increase the sustainability of management of water resources in the Selangor catchment. This paper describes the approach developed to support LUAS meet this objective, in a manner that can be used in real-time, and which can be transferred to other catchments in future. The advantages and disadvantages of potentially expanding this system to use ensemble forecasts, data assimilation and optimisation algorithms are discussed, along with suggestions for further research
Shipbuilding docks as experimental systems for realistic assessments of anthropogenic stressors on marine organisms
No full textEmpirical investigations of the impacts of anthropogenic stressors on marine organisms are typically performed under controlled laboratory conditions, onshore mesocosms, or via offshore experiments with realistic (but uncontrolled) environmental variation. These approaches have merits, but onshore setups are generally small sized and fail to recreate natural stressor fields, whereas offshore studies are often compromised by confounding factors. We suggest the use of flooded shipbuilding docks to allow studying realistic exposure to stressors and their impacts on the intra- and interspecific responses of animals. Shipbuilding docks permit the careful study of groups of known animals, including the evaluation of their behavioral interactions, while enabling full control of the stressor and many environmental conditions. We propose that this approach could be used for assessing the impacts of prominent anthropogenic stressors, including chemicals, ocean warming, and sound. Results from shipbuilding-dock studies could allow improved parameterization of predictive models relating to the environmental risks and population consequences of anthropogenic stressors
How do our flood defences perform during floods? Ten years of lessons learned and putting them into practice
No full textFlood defences are only called into action a few times in their life, so if a large flood does occur, it is important to learn from their performance. The Environment Agency have carried out a structured review of defence performance after each of the major events since the 2007 Summer floods, up to and including the winter 2015/16 floods. These reviews have focused on lessons learned for asset management, at both local and national scale. This presentation will look back over the six reviews carried out in that period, drawing out overarching conclusions about how English flood defences perform during floods based on real life experience, and how this has driven and is driving improvements to asset management and design, supported by research.
The six reviews covered all major breaches or near-breaches, but also assessed assets that survived against the odds. Each review typically started with site visits to collate factual information but also to understand the local asset managers’ point of view and collect anecdotal evidence, essential to establish the story of the flood event. This was used to determine the failure modes that occurred, supported by hydraulic/geotechnical modelling as required.
Key conclusions were that visual condition can only tell so much about risk of breach, and that local irregularities are often the trigger for failure. This has influenced how the Environment Agency prioritises its asset management investment in relation to Condition Grade, and has initiated focused studies to identify weak points such as transitions and historical channel crossings
Exploring structural stability of old blockwork breakwaters
No full textMany old coastal harbours in the UK are protected by blockwork breakwaters, but the original streams of income for maintaining or refurbishing these structures have largely diminished. Foundation settlement, loss of mortar, missing blocks, and voiding behind walls or under decks all tend to destabilise these breakwaters, and have in some cases led to localised or complete failures. Those who manage these assets may benefit from an answer to the question: what happens if they fall down? This paper presents results from an exploratory study of these structures’ strength, stability, collapse mechanisms, and collapsed form. Construction details and dimensions are extracted from historical documents and an analytical spreadsheet model is used to guide the design of physical model tests in the flume. These tests show sensible collapse mechanisms, despite challenges of scale and model effects. Profile measurements are plotted over the test series, showing the progression of front and rear wall failure, and the collapsed crest level. The companion paper by Allsop et al (2017) presents and discusses the residual wave protection offered by these failed breakwaters