- Dr Valentin Heller is currently an Associate Professor in Hydraulics in the Department of Civil Engineering at the Un... moreDr Valentin Heller is currently an Associate Professor in Hydraulics in the Department of Civil Engineering at the University of Nottingham and a member of the Environmental Fluid Mechanics and Geoprocesses Research Group. Before moving to the University of Nottingham, he held one of the prestigious Imperial College London Research Fellowships, a Research Fellowship at the University of Southampton and a postdoctoral position at ETH Zurich. He received his PhD and MSc in Civil Engineering from ETH Zurich. His research mainly concerns experimental fluid dynamics into landslide-tsunamis (impulse waves), marine renewables and scale effects in fluids and granular slides. Dr Heller and his research team further apply a wide range of computational fluid dynamics CFD, and other, codes such as DualSPHysics, OpenFOAM, SWASH and LIGGGHTS-DEM.edit
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.