Danish Hydraulic Institute

Horsholm, Denmark

Danish Hydraulic Institute

Horsholm, Denmark
Time filter
Source Type

O'Boyle L.,Queen's University of Belfast | Elsasser B.,Queen's University of Belfast | Elsasser B.,Danish Hydraulic Institute | Whittaker T.,Queen's University of Belfast
Sustainability (Switzerland) | Year: 2017

Wave energy converters (WECs) inherently extract energy from incident waves. For wave energy to become a significant power provider in the future, large farms of WECs will be required. This scale of energy extraction will increase the potential for changes in the local wave field and coastal environment. Assessment of these effects is necessary to inform decisions on the layout of wave farms for optimum power output and minimum environmental impact, as well as on potential site selection. An experimental campaign to map, at high resolution, the wave field variation around arrays of 5 oscillating water column WECs and a methodology for extracting scattered and radiated waves is presented. The results highlight the importance of accounting for the full extent of the WEC behavior when assessing impacts on the wave field. The effect of radiated waves on the wave field is not immediately apparent when considering changes to the entire wave spectrum, nor when observing changes in wave climate due to scattered and radiated waves superimposed together. The results show that radiated waves may account for up to 50% of the effects on wave climate in the near field in particular operating conditions. © 2017 by the authors.

Cronin K.,Deltares | Cronin K.,University College Cork | Devoy R.J.D.,University College Cork | Montserrat F.,Danish Hydraulic Institute | Montserrat F.,Netherlands Institute of Ecology
Journal of Coastal Research | Year: 2011

On short timescales of days to weeks, sediment transport in coastal and estuarine environments may be investigated using a tracer technique. This paper describes a set of experiments using fluorescent tracer particles on the intertidal sand flats of the Argideen Estuary, south coast of Ireland, to examine the use of a fluorescent tracer to determine sediment transport patterns as part of a validation dataset for a morphological model. The spatial and temporal limits of this methodology were also assessed. Fluorescent tracer particles were mixed with sand taken from the site and moulded into 0.3 m by 0.3 m plates, deployed at different locations on the sand flats, at different times of the year. A lagrangian sampling approach was used to assess the direction and to estimate the magnitude of tracer transport. A series of short cores were taken over a gridded network of points around each plate, at different time intervals after each deployment. The number of tracer particles found in each core was semi-quantified. Several experiments were carried out throughout the estuary to test the method and it is shown that it was useful to both qualitatively and semi-quantitatively determine the dominant direction of sediment transport at each location. Tracer patterns are clear and consistent enough between the experiments to justify the determination of the sediment transport pathways and therefore provided a useful method of validating the sediment transport pathways simulated with the model.

Liu H.,Beijing Normal University | Ding Y.,Beijing Normal University | Li M.,Beijing Normal University | Lin P.,Danish Hydraulic Institute | And 2 more authors.
River Research and Applications | Year: 2015

In this study, a two-dimensional hybrid numerical model for sediment transport based on lattice Boltzmann method and finite difference method is presented. The governing equations for water flow and suspended sediment transport are the shallow water equations and the advection-diffusion equations, respectively. Sediment load is also involved, so that riverbed deformation is numerically simulated. The model is verified by testing transportation of bank-slump sediment in a sharp bended channel with the comparison to the results of well-accepted finite volume method, illustrating the effectiveness of the proposed hybrid model. © 2014 John Wiley & Sons, Ltd.

Lorke S.,RWTH Aachen | Bruning A.,RWTH Aachen | Van Der Meer J.,Van der Meer Consulting B.V | Schuttrumpf H.,RWTH Aachen | And 7 more authors.
Proceedings of the Coastal Engineering Conference | Year: 2010

Intention of the project FlowDike-D is to quantify the impacts of current and wind on wave run-up and wave overtopping and to consider these processes in existing design formulae for estuarine, river and sea dikes. Physical model tests were carried out in the shallow water basin at DHI (Hørsholm/ Denmark) for two different dike geometries (1:3 and 1:6 sloped dike). The paper introduces the model setup and test programme followed by a short description of the applied instrumentation. The test results for wave run-up and wave overtopping with oblique and non-oblique wave attack, but without current, correspond well with existing formulae from the EurOtop-Manual (2007). The influence of current parallel to the dike combined with different angles of wave attack on wave overtopping and wave run-up has been quantified. A distinction was made between wave attack with and against the current.

Bach S.S.,Maersk Oil | Skov H.,Danish Hydraulic Institute | Piper W.,Biologisch landschaftsokologische Arbeitsgemeinschaft
Society of Petroleum Engineers - SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production 2010 | Year: 2010

Acoustic monitoring of small cetaceans (harbour porpoises and dolphins) has been conducted around two platforms in the central North Sea. At one platform, there was continuous drilling activity while at the other platform, drilling did not occur during the monitoring period. The objective was to assess activity of harbour porpoises, Phocoena phocoena, around the platforms and assess the behavioural effects from sound emissions related to drilling activities. Passive acoustic monitoring devices (PAMs - T-POD ver. 5) were deployed at both locations for a period of more than two years. The PAMs are able to detect high frequency sound from small cetaceans and thereby assess the activity of animals in the immediate area surrounding the platforms. The results indicate that there is a relatively high activity of harbour porpoises around both the observed offshore platforms throughout the year. Clear seasonal trends in acoustic activities were not observed aside from increased activity levels during the fall of 2007 and in the late fall of 2008 at both locations. It is possible that these events are the results of a movement of harbour porpoises away from the calving grounds to the offshore areas. The offshore structures are known to attract fish and could function as feeding stations for the harbour porpoises, i.e. the platforms most likely function as artificial reefs. Hydrographic conditions at the platform locations that could influence the availability of prey in the area will naturally influence the activity level of the harbour porpoises. The study indicates that offshore platforms and drilling activities do not pose a significant threat to small cetaceans. However, the results show that short-term behavioural effects must be expected during activities that result in high sound intensity levels, e.g. during the ramming of conductors. The study confirms that PAMs are a useful tool for monitoring behavioural changes of small cetaceans in offshore environments. However, rough weather conditions and the risk of collision with vessels present a challenge. Loss of equipment and consequently loss of data is very likely to happen. In addition, the costs of maintaining the equipment and retrieving the data are significant due to the remote location. Consequently, the use of PAMs should be carefully considered when assessing the purpose of the monitoring. Copyright 2010, Society of Petroleum Engineers.

Brankovic M.,JP Kenny Pty Ltd. | Zeitoun H.,JP Kenny Pty Ltd. | Sutherland J.,HR Wallingford | Pearce A.,Woodside Energy | And 5 more authors.
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2010

One of the aspects of pipeline design is ensuring pipeline stability on the seabed under the action of environmental loads. During the 1980s, significant efforts were made to improve the understanding of hydrodynamic loads on single pipeline configurations on the seabed (Reference 1). The stability of piggyback (bundled) pipeline configurations is less well understood, with little quantitative data readily available to the design engineer for practical application in engineering problems (References 2-6). This paper describes an extensive set of physical model tests performed for piggyback on-seabed and piggyback-raised-from seabed (spanning or lifting pipeline) configurations to determine hydrodynamic forces in combined wave and current conditions. The piggyback is nominally in the 12 o'clock position. The well-established carriage technique was used, in order to obtain data for use in full-scale stability modelling. The model tests are benchmarked against existing test data, to confirm the validity of the test method. Key findings are presented in terms of non-dimensional coefficients, and force time histories for the vertical and horizontal forces. A brief interpretation of the hydrodynamic load behaviour of the Piggyback System is provided by considering the physical flow mechanisms causing the force time history variation; furthermore the influence of the seabed separation on the piggyback loads is also discussed. © 2010 by ASME.

Larsen T.J.,Technical University of Denmark | Kallesoe B.S.,Technical University of Denmark | Hansen H.F.,Danish Hydraulic Institute
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2011

In this paper we present a comparison between simulated and measured loads and dynamic motions for the floating wave energy platform Poseidon equipped with three wind turbines. In order to simulate the response of the system, the aeroelastic code HAWC2 which is state-of-the-art within wind turbine simulation has been extended to handle multiple rotors and is coupled to the time-domain diffraction/radiation solver for floating systems WAMSIM from the Danish Hydraulic Institute. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

Madin J.,University of Malaya | Chong V.C.,University of Malaya | Hartstein N.D.,Northwest Atlantic Fisheries Center | Hartstein N.D.,Danish Hydraulic Institute
Aquaculture Research | Year: 2010

The effects of water flow, fish feed and cage position on net biofouling was examined in a floating cage fish farm. Fouling of 16 mm mesh net panels suspended inside and outside net cages and exposed to different treatments were monitored weekly until net apertures were completely occluded by the fouling organisms (8 weeks). Results indicate a dramatic reduction in water flow velocity throughout the fish farm due to the cage units themselves and net biofouling. The reduced water flow (<10 cm s-1) inside net cages promoted rapid net biofouling, while rapid water flow outside the net cages (>25 cm s-1) kept the net fouling organisms at bay. Although fish rearing in net cages with inputs of commercial pellet feed increased sessile biofouling (222% higher than outside the net cages) and non-sessile biofouling (570% higher), the type of fish feed used did not significantly affect biofouling development. The study recommends that the geometry of serially arranged net cages, as commonly deployed in tropical tidal estuaries, be reconfigured to improve flow through in order to minimize the impact of fouling. © 2010 The Authors. Aquaculture Research © 2010 Blackwell Publishing Ltd.

Amponsah O.,Kwame Nkrumah University Of Science And Technology | Vigre H.,Technical University of Denmark | Schou T.W.,Danish Hydraulic Institute | Boateng E.S.,Kwame Nkrumah University Of Science And Technology | And 2 more authors.
Resources, Conservation and Recycling | Year: 2015

We sought to understand the factors that have undermined the effective implementation of the low quality water reuse provision in Ghana's Irrigation Policy. Two Strategic Environmental Assessment tools (i.e. compatibility matrix and sustainability test) were used for the policy analyses. The analyses identified neither conflicts nor sustainability issues which could undermine the effective implementation of the policy in Ghana. Rather, its effective implementation was found to be the result of the lack of supportive legislation, regulations and guidelines. Furthermore, most of the institutions, which have been identified as key stakeholders for the policy implementation, not only lack the commitment to implement the policy but also perceive low quality water reuse as a practice that can endanger public health. We conclude that effective implementation of the low quality water reuse policy requires an integration of the policy into the broader water resources management context supported with legislation and regulations which spell out clearly institutional responsibilities, and rewards and punishments for compliance or otherwise. © 2015 Published by Elsevier B.V.

Loading Danish Hydraulic Institute collaborators
Loading Danish Hydraulic Institute collaborators