Land ice melt and retreat is one of the most visible effects of climate change and contributes ≈1.5 mm/year to global sea-level rise (SLR) of a total of ≈2.7 mm/year. Global warming results in the shrinking of ice masses in most ice... more
Land ice melt and retreat is one of the most visible effects of climate change and contributes ≈1.5 mm/year to global sea-level rise (SLR) of a total of ≈2.7 mm/year. Global warming results in the shrinking of ice masses in most ice covered regions in the World, particularly in the Alps and in Greenland and the Greenlandic mass loss is estimated at –269 ±51 Gt/year. A significant part of this mass loss is through the detachment of icebergs at glacier fronts in a mechanism called iceberg calving. Such iceberg impacting into a water body generate tsunamis, such called "iceberg-tsunamis". Such an iceberg-tsunami reached a height of 50 m at the Eqip Sermia outlet glacier in 2014. These tsunamis pose a considerable hazard for the local community, the fishing industry and the increasing number of tourists in ice covered areas. Several iceberg calving mechanisms have been proposed including fall, over-turning and capsizing. Reliable guidance on the upper limit of iceberg-tsunami heights are currently unavailable. A main reason for this limited understanding is that reliable field data are rare, such that laboratory tests complemented with numerical simulations are important to advance this research field. This was the aim of this HYDRALAB+ funded study. The wave features (height, length, velocity) caused by icebergs in function of the iceberg calving mechanisms (fall, over-turning, capsizing), as well as the mass volume and kinematics, were modelled in unique large-scale experiments. This minimised both scale effects and wave reflection. The attached files and folders include information about and data from these experiments.
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Land ice melt and retreat is one of the most visible effects of climate change and contributes ≈1.5 mm/year to global sea-level rise (SLR) of a total of ≈2.7 mm/year. Global warming results in the shrinking of ice masses in most ice... more
Land ice melt and retreat is one of the most visible effects of climate change and contributes ≈1.5 mm/year to global sea-level rise (SLR) of a total of ≈2.7 mm/year. Global warming results in the shrinking of ice masses in most ice covered regions in the World, particularly in the Alps and in Greenland and the Greenlandic mass loss is estimated at –269 ±51 Gt/year. A significant part of this mass loss is through the detachment of icebergs at glacier fronts in a mechanism called iceberg calving. Such iceberg impacting into a water body generate tsunamis, such called "iceberg-tsunamis". Such an iceberg-tsunami reached a height of 50 m at the Eqip Sermia outlet glacier in 2014. These tsunamis pose a considerable hazard for the local community, the fishing industry and the increasing number of tourists in ice covered areas. Several iceberg calving mechanisms have been proposed including fall, over-turning and capsizing. Reliable guidance on the upper limit of iceberg-tsunami heights are currently unavailable. A main reason for this limited understanding is that reliable field data are rare, such that laboratory tests complemented with numerical simulations are important to advance this research field. This was the aim of this HYDRALAB+ funded study. The wave features (height, length, velocity) caused by icebergs in function of the iceberg calving mechanisms (fall, over-turning, capsizing), as well as the mass volume and kinematics, were modelled in unique large-scale experiments. This minimised both scale effects and wave reflection. The attached file is an HYDRALAB+ standard Data Storage Report about these experiments.
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Ski jumps are a major element of each dam spillway because these are the only structures able to accomplish satisfactory energy dissipation for takeoff velocities in excess of some 20 m / s. This research aims to add to several hydraulic... more
Ski jumps are a major element of each dam spillway because these are the only structures able to accomplish satisfactory energy dissipation for takeoff velocities in excess of some 20 m / s. This research aims to add to several hydraulic problems with ski jumps that have not yet been systematically solved so far. Based on an experimental campaign, the following problems were addressed: ~1! pressure head maximum and pressure distribution along a circular-shaped flip bucket; ~2! takeoff characteristics for a certain bucket deflection and a relative bucket curvature including the jet trajectories of both the lower and the upper nappes; ~3! impact characteristics in a prismatic tailwater channel with details of shock wave formation and height of recirculation depth; ~4! energy dissipation across the ski jump, from the upstream channel to downstream of jet impact; and ~5! choking flow conditions by the flip bucket. These results demonstrated the significant effect of the approach Froude number, the relative bucket curvature and the bucket angle. The results allow immediate application to the design of ski jumps in hydraulic engineering.
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... Velocimetry PIV, and the wave profiles measured with seven Capacitance Wave Gages CWGs. Item Type: Article. Additional Information: Test 7. Experimental SPH validation. Related URLs: http://wiki.manchester.ac.uk/s....php/Test7. ...
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Research Interests: Mechanical Engineering, Aerospace Engineering, Geology, Mechanics, Hydraulics, and 15 moreTurbulence, Literature Review, Turbulent boundary layer, Water Waves, Wave propagation, Tc, Spectrum, Surface Tension, Scale Effect, Interdisciplinary Engineering, Air Entrainment, Boundary Layer, Attenuation, Amplitude, and Froude number
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This chapter gives an overview of the development of wave energy converters (WECs) from initial conception to commercial demonstration. The structure of the chapter follows the Technology Readiness Level (TRL) approach, as recommended by... more
This chapter gives an overview of the development of wave energy converters (WECs) from initial conception to commercial demonstration. The structure of the chapter follows the Technology Readiness Level (TRL) approach, as recommended by several documents for the development of WECs. An overview about the TRL approach is given in Section 8.04.1. The development of a device requires substantial fiscal support and funding opportunities. These opportunities, focusing on the UK, are reviewed in Section 8.04.2, together with further benefits for device developers as a result of funded activities. Physical model testing in the laboratory is an essential part in the research and development of WECs. Section 8.04.3 addresses those phases of TRLs (TRL 1–3) taking place in the laboratory environment. The first part of this section addresses similarity theory and scale effects and shows how the results in the model can be up-scaled to full scale. The second part describes the design and testing of physical scale models including topics such as test facilities, wave generation methods, model design, measurement equipment, or testing the device under different wave conditions. In contrast to tests under laboratory conditions, the ocean environment is not controllable and investigations are much more expensive and time consuming. Such tests taking place in the sea (TRL 3–5) are covered in Section 8.04.4. Tests conducted at a benign test site, which are still based on a scaled version of the device, are covered first. Then some information about sea trials based on full-scale prototypes is reviewed. The last part of this section addresses sea trials with WECs in arrays. Irrespective of the TRL test phase, there exists two basic approaches to analyze the measured data namely frequency domain and time domain analysis. These two approaches are described in the final Section 8.04.5 of this chapter.
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... Source: COASTAL ENGINEERING 2008 (pp 1313-1325). Author(s): Valentin Heller Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland. ... Full Text: View full text in PDF format (1931KB). TOC:... more
... Source: COASTAL ENGINEERING 2008 (pp 1313-1325). Author(s): Valentin Heller Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland. ... Full Text: View full text in PDF format (1931KB). TOC: Back to Table of Contents. ...
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ABSTRACT Ski jumps are a standard element of dam spillways for an efficient energy dissipation if takeoff velocities are large, and stilling basins cannot be applied. This laboratory study investigates the hydraulic performance of a... more
ABSTRACT Ski jumps are a standard element of dam spillways for an efficient energy dissipation if takeoff velocities are large, and stilling basins cannot be applied. This laboratory study investigates the hydraulic performance of a triangular-shaped, rather than the conventional circular-shaped, bucket placed at the takeoff of ski jumps. The following items were addressed: 1 pressure head maximum and pressure distribution along the triangular-shaped bucket; 2 takeoff characteristics as a function of the bucket deflector angle and the relative bucket height including the lower and the upper jet trajectories; 3 jet impact characteristics in a prismatic tailwater channel including the shock wave formation and the height of recirculation depth below the jet cavity; 4 energy dissipation across the ski jump, from the approach flow channel to downstream of jet impact; and 5 choking flow conditions of the flip bucket. A significant effect of the approach flow Froude number, the relative bucket height, and the deflector angle is found. A comparison with previous results for the circular-shaped bucket geometry indicates a favorable behavior of the novel bucket design.
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Massstabseffekte entsprechen einer Verzerrung der Messwerte im Modell gegenuber dem Prototypen. Jedes hydraulische Modell eines Prototypen mit Modellmassstab ungleich eins weist solche Massstabseffekte auf. Wird aber das Modell genugend... more
Massstabseffekte entsprechen einer Verzerrung der Messwerte im Modell gegenuber dem Prototypen. Jedes hydraulische Modell eines Prototypen mit Modellmassstab ungleich eins weist solche Massstabseffekte auf. Wird aber das Modell genugend gross gebaut, so sind diese Effekte vernachlassigbar klein, und die Messresultate konnen mittels Modellgesetz auf den Prototypen ubertragen werden. Nachfolgend wird in die Problematik der Massstabseffekte eingefuhrt unter Berucksichtigung der weiterfuhrenden Literatur. Einige grundlegende Schwierigkeiten beim Modellieren von Naturzustanden im hydraulischen Modell werden zudem aufgezeigt. Am Beispiel rutscherzeugter Impulswellen wird die Modellahnlichkeit zwischen Modell und Prototyp verdeutlicht, und weitere Erfahrungswerte zur Vermeidung von grossen Massstabseffekten werden fur verschiedene Prozesse aufgefuhrt. Scale effects correspond to a distortion of the measured values in the model to the prototype. Each hydraulic model of a prototype model with a scale equal to one has such scale effects. But if the model built big enough, these effects are negligible, and the measurement results can be transferred to the prototype model by means of law. Below is introduced into the problem of scale effects, taking into account the secondary literature. Some fundamental difficulties in modeling of natural conditions in the hydraulic model are also shown. The example rutscherzeugter pulse waves the model similarity between model and prototype is demonstrated, and further experiences to avoid large-scale effects are listed for different processes.
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Research Interests: Physics, Mechanics, Turbulence, Vorticity, Laminar Flow, and 3 moreVortex, Reynolds Number, and Froude number
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... (i) piston amplitude 0.037 m ≤ aP ≤ 0.201 m and (ii) piston period 1.0 s ≤ TP ≤ 2.5 s ... RESULTS Bulge wave speed The bulge wave speed cb of the Anaconda has to be close to the external wave celerity to reach resonance with maximised... more
... (i) piston amplitude 0.037 m ≤ aP ≤ 0.201 m and (ii) piston period 1.0 s ≤ TP ≤ 2.5 s ... RESULTS Bulge wave speed The bulge wave speed cb of the Anaconda has to be close to the external wave celerity to reach resonance with maximised power output (Chaplin et al., 2007). ...
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Ski jumping - general design approache
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ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized... more
ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized water body geometry applies best to a specific prototype. Hence, a physical small-scale model study has been conducted that, for the first time, systematically investigates the effect of geometry on landslide-generated tsunami height, amplitude, period, and celerity. A rigid slide generated tsunamis propagating in various geometries characterized by the basin side angle theta. Considered were 2D (theta = 0 degrees), 3D (theta = 90 degrees), and six intermediate geometries. The differences between 2D and 3D wave heights were found to be about 20% at a distance of five times the water depth from the slide impact zone, but increased with increasing distance. It is shown that the 3D case applies on a much wider prototype range than the 2D case because it approximates the wave features on the slide axis for all investigated geometries with theta > 30 degrees. The energy flux conservation based on the given 2D results can predict wave heights for the remaining geometries with theta <= 30 degrees. The implications of the present results in practice are discussed and an example illustrates how the results support tsunami hazard assessment despite significant scale effects. DOI: 10.1061/(ASCE)WW.1943-5460.0000130.(C) 2012 American Society of Civil Engineers.
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Earthquake-tsunamis, including the 2004 Indian Ocean Tsunami, with approximately 227,898 casualties, and the 2011 Tōhoku Tsunami in Japan, with 18,550 people missing or dead [...]
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This study presents a numerical landslide-tsunami hazard assessment technique for applications in reservoirs, lakes, fjords, and the sea. This technique is illustrated with hypothetical scenarios at Es Vedrà, offshore Ibiza, although... more
This study presents a numerical landslide-tsunami hazard assessment technique for applications in reservoirs, lakes, fjords, and the sea. This technique is illustrated with hypothetical scenarios at Es Vedrà, offshore Ibiza, although currently no evidence suggests that this island may become unstable. The two selected scenarios include two particularly vulnerable locations, namely: (i) Cala d’Hort on Ibiza (3 km away from Es Vedrà) and (ii) Marina de Formentera (23 km away from Es Vedrà). The violent wave generation process is modelled with the meshless Lagrangian method smoothed particle hydrodynamics. Further offshore, the simulations are continued with the less computational expensive code SWASH (Simulating WAves till SHore), which is based on the non-hydrostatic non-linear shallow water equations that are capable of considering bottom friction and frequency dispersion. The up to 133-m high tsunamis decay relatively fast with distance from Es Vedrà; the wave height 5 m offshore C...
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Subaerial landslide-tsunamis (SLTs) are caused by mass movements such as landslides, rock falls or glacier calving. Research into SLTs is ongoing for many decades, however, the advancement in the physical understanding and reliability of... more
Subaerial landslide-tsunamis (SLTs) are caused by mass movements such as landslides, rock falls or glacier calving. Research into SLTs is ongoing for many decades, however, the advancement in the physical understanding and reliability of hazard assessment methods is not reflecting the number of articles published per year. It appears that a paradigm shift in SLT research is required for a genuine advancement. This article critically reviews the state-of-the-art of SLT research, highlights current limitations and introduces potential candidates to perform this needed paradigm shift.
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flow, notably how the flow interacts with a boundary, be it a bed of particles or the interface with an another fluid. The altered interaction, in turn, changes the flow field. The statistics associated with large-scale turbulence... more
flow, notably how the flow interacts with a boundary, be it a bed of particles or the interface with an another fluid. The altered interaction, in turn, changes the flow field. The statistics associated with large-scale turbulence structures and their effects on entrainment and transport processes at boundaries require further investigation in hydraulic modelling and experiments. How altered spectra of turbulence-derived fluctuations in velocity and pressure interact with a deformable boundary and affect the resulting waveforms (on a sediment bed or at an air–water surface) raises interesting questions. For example, it is well known (e.g. Raudkivi, 1998) that, in turbulent flow, the hydrodynamic force on a boundary is a markedly fluctuating quantity that has significant implications for entrainment and movement of particles, and thereby bed wave development. The need for further investigation grows when the primary modelling criterion departs from Froude modelling, and instead focuses on an entrainment criterion, as is the case for modelling bed-particle or air entrainment. Departure from strict Froude modelling quickly raises an issue regarding exaggeration of vorticity in turbulence structures such as wake eddies. The Froude modelling situations the writer mentions (flows involving hydraulic structures and/or deformable boundaries) perhaps may slip outside the realm of the true self-similarity, but they are common modelling situations. Most hydraulic modelling of hydraulic structures at reduced scale uses Froude modelling and for practical reasons cannot resort to Reynold modelling to get the flow details right. Froude-based hydraulic modelling requires recognizing the inherent approximations involved, designing the model to yield the necessary information about the main process under scrutiny, and knowing how potential scale effects may impact that information. Heller’s interesting paper elevates the level of scientific discussion regarding similitude in hydraulic modelling and laboratory experimentation. The Discusser enjoyed reading the paper and is interested to learn Heller’s thoughts regarding the two points the Discusser mentions. References
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Abstract: The significance of the impulse product parameter P is reviewed, which is believed to be the most universal parameter for subaerial landslide tsunami (impulse wave) prediction. This semi-empirical parameter is based on the... more
Abstract: The significance of the impulse product parameter P is reviewed, which is believed to be the most universal parameter for subaerial landslide tsunami (impulse wave) prediction. This semi-empirical parameter is based on the streamwise slide momentum flux component and it was refined with a multiple regression laboratory data analysis. Empirical equations based on P allow for a simple prediction of wave features under diverse conditions (landslides and ice masses, granular and block slides, etc.). Analytical evidence reveals that a mass sliding down a hill slope of angle 51.6 ° results in the highest waves. The wave height ―observed ‖ in the 1958 Lituya Bay case was well predicted using P. Other real-world case studies illustrate how efficient empirical equations based on P deliver wave estimates which support hazard assessment. Future applications are hoped to further confirm the applicability of P to cases with more complex water body geometries and bathymetries.
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Subaerial landslide-tsunamis (impulse waves) are generated by mass movements such as landslides, rock falls or glacier calving interacting with a water body. Preliminary landslide-tsunami hazard assessment is commonly based on empirical... more
Subaerial landslide-tsunamis (impulse waves) are generated by mass movements such as landslides, rock falls or glacier calving interacting with a water body. Preliminary landslide-tsunami hazard assessment is commonly based on empirical equations derived from wave channel (2D) or wave basin (3D) experiments. It is crucial to select the most appropriate set of empirical equations for a particular case as the difference in the far-field wave height between 2D and 3D may exceed an order of magnitude. The present study systematically investigates the effect of the water body geometry on the wave characteristics. Physical model tests were conducted in 2D and repeated in 3D, involving two water depths, three rigid slides and different subaerial slide release positions. The waves were found to decay in 2D considerably slower with distance x ‒0.30 than in 3D with radial distance r ‒1.0. The 3D wave heights in the slide impact zone can be identical large as in 2D for a large slide Froude num...
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A widely applied model strategy in experimental fluid dynamics is to conduct laboratory experiments at reduced scale in the Reynolds number R invariant regime to ensure that the turbulent behaviour in the field situation is correctly... more
A widely applied model strategy in experimental fluid dynamics is to conduct laboratory experiments at reduced scale in the Reynolds number R invariant regime to ensure that the turbulent behaviour in the field situation is correctly modelled. This study investigates R invariance and quantifies R scale effects in dissipative-type shallow-water vortices where R invariance can naturally not be maintained. A laboratory scale series of monopole shallow-water vortices was conducted in a circular domain with rotating bottomless cylinders. Froude scale ratios were applied to carefully scale all experimental parameters between three scales, apart from the kinematic viscosity. Surface particle image velocimetry was conducted to record the vortex decay. The radial-averaged azimuthal velocity over radial distance and the ensemble-averaged mean azimuthal velocity, Reynolds number and dimensionless vorticity decays are presented. A similar pattern in the initial turbulent regime is observed in a...
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Landslides, rockfalls, and iceberg calving impacting into a water body generate large landslide-tsunamis posing a serious hazard in lakes and reservoirs. These waves can impact and even overtop dams as in the 1963 Vajont disaster in... more
Landslides, rockfalls, and iceberg calving impacting into a water body generate large landslide-tsunamis posing a serious hazard in lakes and reservoirs. These waves can impact and even overtop dams as in the 1963 Vajont disaster in Italy. However, estimating the effects of tsunamis on dams, e.g. pressures and forces, and 3D effects is challenging. An accurate prediction of these effects is also important for a range of coastal and offshore applications. The present study focuses on the numerical modelling of landslide-tsunamis impacting dams with the open source toolbox solids4foam. After a validation with theoretical, experimental, and numerical results, 5th order Stokes, cnoidal, and solitary waves were simulated in 72 2D experiments with dams of steep to vertical inclinations. The wave loading on dams was found to be in agreement with predictions based on an existing empirical approach, significantly expanding its limited validation conditions. New empirical equations are sugges...
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The first tests of the Anaconda wavepower device to be carried out in a wave basin revealed some shortcomings in the novel instrumentation that was required to record the response of the device in waves, and usefully capture wave power... more
The first tests of the Anaconda wavepower device to be carried out in a wave basin revealed some shortcomings in the novel instrumentation that was required to record the response of the device in waves, and usefully capture wave power under laboratory conditions. The most valuable measurements were those of water waves radiated by propagating bulge waves. At present there is no theoretical framework with which to compare these data.
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Glaciers calving icebergs into the ocean significantly contribute to sea-level rise and can trigger tsunamis, posing severe hazards for coastal regions. Computational modeling of such multiphase processes is a great challenge involving... more
Glaciers calving icebergs into the ocean significantly contribute to sea-level rise and can trigger tsunamis, posing severe hazards for coastal regions. Computational modeling of such multiphase processes is a great challenge involving complex solid–fluid interactions. Here, a new continuum damage Material Point Method has been developed to model dynamic glacier fracture under the combined effects of gravity and buoyancy, as well as the subsequent propagation of tsunami-like waves induced by released icebergs. We reproduce the main features of tsunamis obtained in laboratory experiments as well as calving characteristics, the iceberg size, tsunami amplitude and wave speed measured at Eqip Sermia, an ocean-terminating outlet glacier of the Greenland ice sheet. Our hybrid approach constitutes important progress towards the modeling of solid–fluid interactions, and has the potential to contribute to refining empirical calving laws used in large-scale earth-system models as well as to i...
The Froude scaling laws have been used to model a wide range of water flows at reduced size for almost a century. In such Froude scale models, significant scale effects for air–water flows (e.g. hydraulic jumps or wave breaking) are... more
The Froude scaling laws have been used to model a wide range of water flows at reduced size for almost a century. In such Froude scale models, significant scale effects for air–water flows (e.g. hydraulic jumps or wave breaking) are typically observed. This study introduces novel scaling laws, excluding scale effects in the modelling of air–water flows. This is achieved by deriving the conditions under which the governing equations are self-similar. The one-parameter Lie group of point-scaling transformations is applied to the Reynolds-averaged Navier–Stokes equations, including surface tension effects. The scaling relationships between variables are derived for the flow variables, fluid properties and initial and boundary conditions. Numerical simulations are conducted to validate the novel scaling laws for (i) a dam break flow interacting with an obstacle and (ii) a vertical plunging water jet. Results for flow variables, void fraction and turbulent kinetic energy are shown to be ...
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Impulse waves in oceans, bays, lakes, or reservoirs are generated by landslides, rock falls, shore instabilities, snow avalanches, glacier calvings, or meteorite impacts. Examples are the 1958 Lituya Bay case in Alaska where the generated... more
Impulse waves in oceans, bays, lakes, or reservoirs are generated by landslides, rock falls, shore instabilities, snow avalanches, glacier calvings, or meteorite impacts. Examples are the 1958 Lituya Bay case in Alaska where the generated impulse wave reached a maximum run-up height of 524 m on the opposite shore or the 1963 Vaiont case in North Italy where an impulse wave overtopped a dam by about 70 m and killed 2,000 people. The mainly passive methods to face such catastrophes include evacuations, water level draw-down, or freeboard control in artificial reservoirs. They require detailed knowledge of the wave features and of the wave effects on the dam or shore line. Numerical methods such as SPH may play an important role in the future in predicting the effects of impulse waves since numerical models may result in more accurate predictions for complex geometries than general physical model studies at lower costs than specific physical case studies (Heller et al. 2009). This test...
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... Velocimetry PIV, and the wave profiles measured with seven Capacitance Wave Gages CWGs. Item Type: Article. Additional Information: Test 7. Experimental SPH validation. Related URLs: http://wiki.manchester.ac.uk/s....php/Test7. ...
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... Source: COASTAL ENGINEERING 2008 (pp 1313-1325). Author(s): Valentin Heller Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland. ... Full Text: View full text in PDF format (1931KB). TOC:... more
... Source: COASTAL ENGINEERING 2008 (pp 1313-1325). Author(s): Valentin Heller Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, CH-8092 Zurich, Switzerland. ... Full Text: View full text in PDF format (1931KB). TOC: Back to Table of Contents. ...
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This research intends to provide a detailed data basis for numerical modelling of impulse waves. Three tests are described involving a rectangular wave channel, in which a trapezoidal ‘breakwater’ was inserted to study wave run-over. In... more
This research intends to provide a detailed data basis for numerical modelling of impulse waves. Three tests are described involving a rectangular wave channel, in which a trapezoidal ‘breakwater’ was inserted to study wave run-over. In addition, a reference test is also described, in which the breakwater was removed. Two-dimensional impulse waves were generated by means of subaerial granular slides accelerated by a pneumatic landslide generator into the water body. Wave propagation and run-over over the artificial breakwater are documented by a set of high-quality photographs. Water surface profiles were recorded using capacitance wave gages upstream and downstream of the breakwater, and velocity vector fields were determined for the run-over zone by means of Particle Image Velocimetry. The measurements are compared with predictive formulae for wave features and wave non-linearity. The present data set involves both simple channel topography and wave features to allow for numerical simulations under basic laboratory conditions.
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Subaerial landslide generated impulse waves were investigated in a prismatic wave channel. Seven governing parameters, namely the still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide... more
Subaerial landslide generated impulse waves were investigated in a prismatic wave channel. Seven governing parameters, namely the still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter, were systematically varied. The generated impulse waves are nonlinear, intermediate- to shallow-water waves involving a small to considerable fluid mass transport. The Stokes
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ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized... more
ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized water body geometry applies best to a specific prototype. Hence, a physical small-scale model study has been conducted that, for the first time, systematically investigates the effect of geometry on landslide-generated tsunami height, amplitude, period, and celerity. A rigid slide generated tsunamis propagating in various geometries characterized by the basin side angle theta. Considered were 2D (theta = 0 degrees), 3D (theta = 90 degrees), and six intermediate geometries. The differences between 2D and 3D wave heights were found to be about 20% at a distance of five times the water depth from the slide impact zone, but increased with increasing distance. It is shown that the 3D case applies on a much wider prototype range than the 2D case because it approximates the wave features on the slide axis for all investigated geometries with theta > 30 degrees. The energy flux conservation based on the given 2D results can predict wave heights for the remaining geometries with theta <= 30 degrees. The implications of the present results in practice are discussed and an example illustrates how the results support tsunami hazard assessment despite significant scale effects. DOI: 10.1061/(ASCE)WW.1943-5460.0000130.(C) 2012 American Society of Civil Engineers.
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ABSTRACT [1] Subaerial landslide-tsunamis and impulse waves are caused by mass movements impacting into a water body, and the hazards they pose have to be reliably assessed. Empirical equations developed with physical Froude model studies... more
ABSTRACT [1] Subaerial landslide-tsunamis and impulse waves are caused by mass movements impacting into a water body, and the hazards they pose have to be reliably assessed. Empirical equations developed with physical Froude model studies can be an efficient method for such predictions. The present study improves this methodology and addresses two significant shortcomings in detail for the first time: these are the effect of three commonly ignored block model parameters and whether the slide is represented by a rigid block or a deformable granular material. A total of 144 block slide tests were conducted in a wave flume under systematic variation of three important block model parameters, the slide Froude number, the relative slide thickness, and the relative slide mass. Empirical equations for the maximum wave amplitude, height, and period as well as their evolution with propagation distance are derived. For most wave parameters, remarkably small data scatter is achieved. The combined influence of the three block model parameters affects the wave amplitude and wave height by up to a factor of two. The newly derived equations for block slides are then related to published equations for granular slides. This comparison reveals that block slides do not necessarily generate larger waves than granular slides, as often argued in the technical literature. In fact, it is shown that they may also generate significant smaller waves. The new findings can readily be integrated in existing hazard assessment methodologies, and they explain a large part of the discrepancy between previously published data.
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Anaconda is a wave energy converter consisting essentially of a closed rubber tube filled with water anchored head to the waves in the sea. Pressure variations due to external waves generate bulge waves in this tube which can be used to... more
Anaconda is a wave energy converter consisting essentially of a closed rubber tube filled with water anchored head to the waves in the sea. Pressure variations due to external waves generate bulge waves in this tube which can be used to produce electrical power with a power take-off system at the tube stern. A test set-up was designed allowing for the generation of bulge waves both in initially still water, mechanically with a moving piston inside the tube, and by external water waves. This article presents experimental results from 156 tests conducted in a 20 m long, 30 m wide and 3 m deep wave basin at Danish Hydraulic Institute. Bulge wave speeds measured by means of strain gauges mounted on the tube are found to be in reasonable agreement with predictions based on linear theory using static measurements of distensibility. The capture width of Anaconda is optimal if the bulge wave speed is close to the external wave celerity. In this condition, measurements of water waves produce...
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Subaerial landslide generated impulse waves were investigated in a prismatic wave channel. Seven governing parameters, namely the still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide... more
Subaerial landslide generated impulse waves were investigated in a prismatic wave channel. Seven governing parameters, namely the still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter, were systematically varied. The generated impulse waves are nonlinear, intermediate- to shallow-water waves involving a small to considerable fluid mass transport. The Stokes
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ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized... more
ABSTRACT Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized water body geometry applies best to a specific prototype. Hence, a physical small-scale model study has been conducted that, for the first time, systematically investigates the effect of geometry on landslide-generated tsunami height, amplitude, period, and celerity. A rigid slide generated tsunamis propagating in various geometries characterized by the basin side angle theta. Considered were 2D (theta = 0 degrees), 3D (theta = 90 degrees), and six intermediate geometries. The differences between 2D and 3D wave heights were found to be about 20% at a distance of five times the water depth from the slide impact zone, but increased with increasing distance. It is shown that the 3D case applies on a much wider prototype range than the 2D case because it approximates the wave features on the slide axis for all investigated geometries with theta > 30 degrees. The energy flux conservation based on the given 2D results can predict wave heights for the remaining geometries with theta <= 30 degrees. The implications of the present results in practice are discussed and an example illustrates how the results support tsunami hazard assessment despite significant scale effects. DOI: 10.1061/(ASCE)WW.1943-5460.0000130.(C) 2012 American Society of Civil Engineers.
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The trajectory parabola commonly used in free jet computation describes the curve of a mass point of constant density under the influence of gravity, depending on the take-off conditions and neglecting jet disintegration as well as... more
The trajectory parabola commonly used in free jet computation describes the curve of a mass point of constant density under the influence of gravity, depending on the take-off conditions and neglecting jet disintegration as well as aerodynamic interaction. Thus, the computed ...