Roman Gabl

CADFEM Austria

An asymmetric orifice can be added to a surge tank of a hydro power plant to dampen the mass oscillation. This allows a reduction of the required volume and a more stable behavior of the overall hydraulic system. In this paper, the advantage of a typical asymmetric orifice is shown in comparison with a sharp-edged geometry with two different pipe d...

Large floating structures, such as liquefied natural gas (LNG) ships, are subject to both internal and external fluid forces. The internal fluid forces may also be detrimental to a vessel’s stability and cause excessive loading regimes when sloshing occurs. Whilst it is relatively easy to measure the motion of external free surface with conventiona...

The experimental set-up allows for the comparison of two different ballast options of a floating cylinder in a wave tank. Four different internal water drafts are tested as well as an equivalent solid ballast option. The model is excited by regular waves, which are characterised with five wave gauges in front of the floating cylinder and two behind...

Hydrodynamic forces are an important input value for the design, navigation and station keeping of underwater Remotely Operated Vehicles (ROVs). The experiment investigated the forces imparted by currents (with representative real world turbulence) and waves on a commercially available ROV, namely the BlueROV2 (Blue Robotics, Torrance, USA). Three...

Understanding the behaviour of water filled bodies is important from an applied engineering perspective when understanding the sea-keeping performance of certain floating platforms and vessels. Even by assuming that the deformation is negligible small in relation to the motion of the structure, these fluid-structure-fluid interactions are challengi...

Tidal energy is one of the world's most predicable renewable energy sources and therefore holds great potential to be a valuable building block for the decarbonisation of electricity production. This paper focuses on a Venturi shaped duct structure (shroud) to accelerate the flow speed at a vertical axis tidal turbine utilising the low static press...

In order to design and evaluate the behaviour of a numerically optimised wave energy converter (WEC), a recommended procedure is to initially study small scale models in controlled laboratory conditions and then progress further up until the full-scale is reached. At any point, an important step is the correct selection of the wave theory to model...

A new white-light volumetric flow measurement technique is presented that can be used in large-scale facilities. The technique enables large volumes to be measured with high temporal and spatial resolution and without the need for a class-4 laser. This LED-based Lagrangian particle tracking velocimetry is demonstrated by measuring the tip vortex fo...

Wave measurement buoys provide characterisation of wave climates that forms the basis for the design of offshore systems. These buoys are commonly subjected to currents which affect the resulting wave measurements, and if not accounted for will result in errors in the estimated sea state parameters. The present work provides results and observation...

One of the main goals of the EU H2020 MaRINET2 project is to improve the quality, robustness and accuracy of physical modelling and testing practices operated by MaRINET2 infrastructures. To achieve this objective, a round robin testing program has been developed where the same device is tested in a number of different infrastructures. The outcomes...

We consider wave forces on fixed porous cylinders with and without a solid inner cylinder and wave-induced motions of floating cylinder with and without a porous outer cylinder. Comparisons between experimental measurements and numerical predictions from an iterative boundary element method (BEM) model are presented. The BEM model assumes that pres...

Force plates are commonly used in tank testing to measure loads acting on the foundation of a structure. These targeted measurements are overlaid by the hydrostatic and dynamic pressure acting on the force plate induced by the waves and currents. This paper presents a dataset of bottom force measurement with a six degree-of-freedom force plate (AMT...

Floating structures have a wide range of application and shapes. This experimental investigations observes a hexagonal floating structure under wave conditions for three different draft configurations. Regular waves as well as a range of white noise tests were conducted to quantify the response amplitude operator (RAO). Further irregular waves focu...

Marine renewable energy (MRE) is still an emerging technology. As such, there is still a lack of mature standards and guidance for the development and testing of these devices. The sector covers a wide range of disciplines, so there is a need for more comprehensive guidance to cover these. This paper builds on a study undertaken in the MaRINET2 pro...

The EU H2020 MaRINET2 project has a goal to improve the quality, robustness and accuracy of physical modelling and associated testing practices for the offshore renewable energy sector. To support this aim, a round robin scale physical modelling test programme was conducted to deploy a common wave energy converter at four wave basins operated by Ma...

Hydropower is an important source of renewable energy. Due to ageing infrastructure, more and more existing hydropower plants have to be refurbished and modernised. This includes a complete review of the design parameters as well as the change of specific parts. Investments should be targeted to improve the overall performance of hydropower plants...

Remotely Operated (underwater) Vehicles (ROV) have a wide range of maritime applications, including repair and maintenance. Quantifying hydrodynamic loads is important for the design and control of these ROVs. A novel approach with eight tethers was used to restrain a commercially available ROV, namely the BlueROV2 (Blue Robotics, Torrance, USA), i...

Floating devices under wave and current loads are typically designed based on numerical methods followed by a validation with experimental investigations. This allows an independent check due to the comparison of two different modelling approaches based on different assumptions. At an early stage of the project, numerical simulations are based on t...

Predictive control methods can substantially improve the performance of Unmanned Underwater Vehicles (UUVs), particularly in shallow water environments or near the free surface where wave induced disturbance are of magnitude comparable to the vehicle characteristic inertia. To facilitate the adoption of these methods, a fast estimation of the time...

Background: This rapid evidence review identifies and integrates evidence from epidemiology, microbiology and fluid dynamics on the transmission of SARS-CoV-2 in indoor environments. Methods: Searches were conducted in May 2020 in PubMed, medRxiv, arXiv, Scopus, WHO COVID-19 database, Compendex & Inspec. We included studies reporting data on any...

The SARS-CoV-2 virus is primarily transmitted through virus-laden fluid particles ejected from the mouth of infected people. Face covers can mitigate the risk of virus transmission but their outward effectiveness is not fully ascertained. Objective: by using a background oriented schlieren technique, we aim to investigate the air flow ejected by a...

We consider wave forces on fixed porous cylinders with and without a solid inner cylinder and wave-induced motions of floating cylinder with and without a porous outer cylinder. Comparisons between experimental measurements and numerical predictions from an iterative boundary element method (BEM) model are presented. The BEM model assumes that pres...

The habilitation thesis links 17 core papers and 22 associated papers. They include methodological approaches as well as case studies for experimental investigations and numerical simulations. The examples presented here include water filled floating structures in a wave tank, asymmetric orifices in a surge tank, velocity distributions in front of...

In this paper, we investigate the dynamics of spherical droplets in the presence of a source–sink pair flow field. The dynamics of the droplets is governed by the Maxey–Riley equation with the Basset–Boussinesq history term neglected. We find that, in the absence of gravity, there are two distinct behaviors for the droplets: small droplets cannot g...

Acoustic Doppler Profilers (ADPs) are routinely used to measure flow velocity in the ocean, enabling multi-points measurement along a profile while Acoustic Doppler Velocimeters (ADVs) are laboratory instruments that provide very precise point velocity measurement. The experimental set-up allows laboratory comparison of measurement from these two i...

Harnessing the energy of tidal currents has huge potential as a source of clean renewable energy. To do so in a reliable and cost effective way, it is critical to understand the interaction between tidal turbines, waves, and turbulent currents in the ocean. Scaled testing in a tank test provides a controlled, realistic, and highly reproducible down...

In this paper, we investigate the dynamics of spherical droplets in the presence of a source-sink pair flow field. The dynamics of the droplets is governed by the Maxey-Riley equation with Basset-Boussinesq history term neglected. We find that, in the absence of gravity, there are two distinct behaviours for the droplets: small droplets cannot go f...

Mass balance analysis of ice sheets is a key component to understand the effects of global warming with iceberg calving as a significant contributor. Calving recently generated tsunamis of up to 50 m in amplitude endangering human beings and coastal infrastructure. Such iceberg-tsunamis (IBTs) have been investigated based on 66 unique large-scale e...

The SARS-CoV-2 virus is primarily transmitted through virus-laden fluid particles ejected from the mouth of infected people. In some countries, the public has been asked to use face covers to mitigate the risk of virus transmission - yet, their outward effectiveness is not ascertained. We used a Background Oriented Schlieren technique to investigat...

The duration of patient–physician contact is an important factor for the optimisation of treatment processes in healthcare systems. Available methods can be labour-intensive and the quality is, in many cases, poor. A part of this research project is to develop a sensor system, which allows the detection of people passing through a door, including t...

Modelling and understanding the motion of water filled floating objects is important for a wide range of applications including the behaviour of ships and floating platforms. Previous studies either investigated only small movements or applied a very specific (ship) geometry. The presented experiments are conducted using the simplified geometry of...

Iceberg calving at outlet glaciers contributes to global sea-level rise in the context of climate change. This study investigates tsunamis generated by iceberg calving, so-called iceberg-tsunamis. Such tsunamis reached amplitudes of 50 m in the recent past and endanger human beings and coastal infrastructure. 66 unique large-scale experiments have...

Iceberg calving at outlet glaciers contributes to global sea-level rise in the context of climate change. This study investigates tsunamis generated by iceberg calving, so-called iceberg-tsunamis. Such tsunamis reached amplitudes of 50 m in the recent past and endanger human beings and coastal infrastructure. 73 unique large-scale experiments have...

The requirements for fish protection at hydro power plants have led to a significant decrease of the bar spacing at trash racks as well as the need of an inclined or angled design to improve the guidance effect (fish-friendly trash racks). The flexible fish fence (FFF) is a new developed fish protection and guidance system, created by horizontally...

Mass balance analysis of ice sheets is a key component to understand the effects of global warming. A significant component of ice sheet and shelf mass balance is iceberg calving, which can generate large tsunamis endangering human beings and coastal infrastructure. Such iceberg-tsunamis have reached amplitudes of 50 m and destroyed harbours. Calvi...

An unexpected and massive redistribution of fine sediment in a large Alpine reservoir was triggered by a further lowering of the water level to conduct maintenance work. This caused the need of a total redesign of the existing head race intake for a high head power plant in the Austrian Alps. Two main geometry options for the trash rack support str...

The addition of an asymmetric orifice is a successful way to limit the influence of the mass oscillation in a hydro power plant. The paper summarises the lat-est research topics and gives an outlook for further developments.

General guidelines are available for the design of intake structures in river power plants. Nearly all existing criteria are limited in scope to a (rectangular) control section near the trash rack. In this section, a homogeneous flow with negligible wall influence is defined as the ideal condition. 3D numerics can simulate the complete velocity fie...

Hydrodynamic flow impacts on obstacles in the flow are difficult to capture and the calculation of these complex flow processes with numerical models is challenging. Therefore, a simplified physical scale model is set up to measure such an impact and deliver experimental results for the calibration of a numerical model with the 3D numerical softwar...

Scale model tests and numerical simulations are the two mainly used methods in hydraulic engineering. The paper describes both modelling techniques, typical scopes of application and as well basic information of costs and required time for the investigations. The positive effects of coupling both methods are exemplarily shown with the example of qu...

For the hydraulic protection of the penstock of a high-head power plant typically a pipe rupture valve is installed. As an alternative to this, a wall can be added in the penstock as a fixed installation. In case of an emergency the gate at the upper reservoir is closed and this local high point allows holding back the water behind. In this paper t...

The investigation of a (complete) failure of a penstock is part of a global risk analysis of a high-pressure hydropower plant. The paper summarizes basic facts about the reason for such events, the process of development and possible ways to reduce the damage caused by such a hazard. In the second part possible modelling strategies for such failure...

Speicherbecken im Pumpbetrieb oder Beschneiungsspeicher können in Zeiträumen großer Lawinengefahr einen hohen Wasserstand aufweisen. In Hinblick auf eine Gefahrenbetrachtung und Risikoabschätzung ist deshalb auch ein möglicher Einstoß einer Lawine in einen gefüllten Speicher zu untersuchen. Der Einstoß einer großen Lawine kann dabei eine Impulswell...

This paper contains the results of an experimental study on head loss through angled screens for fish protection. A physical model on a scale of 1:2 was conducted to assess the effect of the geometry, defined by the angle, bar shape and bar spacing on headloss for a range of flow velocities. The results indicate that headloss increases with increas...

Given the current challenges in flood risk management and vulnerability assessment of buildings exposed to flood hazards, this study presents three-dimensional numerical modelling of torrential floods and its interaction with buildings. By means of a case study application, the FLOW-3D software is applied to the lower reach of the Rio Vallarsa torr...

In den letzten Jahren hielt vermehrt die dreidimensionale (3D-)numerische Strömungssimulation im Bereich der Grundlagenforschung und der Planung von hydraulischen Anlagen Einzug. Rechen im Bereich von Kraftwerkseinläufen stellen jedoch für die numerische Simulation eine besondere Herausforderung dar. Dies ist der, im Vergleich zu anderen Bauteilen,...

Given the current challenges in flood risk management and vulnerability assessment of buildings exposed to flood hazards, three-dimensional numerical modelling of torrential floods and its interaction with buildings are presented. By means of a case study application, the FLOW-3D software is applied to the lower reach of the Rio Vallarsa torrent in...

The impact of an avalanche in a reservoir induces impulse waves, which pose a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting overtopping volume over structures and dams, formulas, which are based on different simplifying assumptions, can be used. Further project-spe...

Slides

Most criteria for the evaluation of velocity distributions (VD) in front of turbines in river power plants are derived for the section of the trash rack. Hence, an optimization of the approaching flow behind this section cannot be evaluated. The paper shows the adaption of the existing and well know Fisher & Franke (F&F) criterion, which was publis...

In case of a massive failure in the penstock of a high-head power plant, pipe-break valves uncouple the nearly horizontal part from the endangered and also mainly strained section. In addition to the prime cost of such valves the operation can be a non-negligible expense factor. In case of the modernisation of an existing power plant the alternativ...

The impact of an avalanche into a reservoir induces an impulse wave, which poses a threat to population and infrastructure. For a good approximation of the generated wave height and length as well as the resulting outflow volume over structures and dams, formulas, which base on different simplifying assumptions, can be used. Further project-specifi...

In der vorliegenden Arbeit werden zwei didaktische Maßnahmen anhand einer Lehrveranstaltung (Vorlesung mit Ubung) aus dem Masterstudium mit 52 HörerInnen der Fakultät für Technische Wissenschaften unter-sucht. Neben den Zusammenfassungen zu Beginn jeder Stunde und der abschließenden Gesamtzusammenfas-sung wurde besonderer Wert auf das Feedback als...

Einlaufrechen gehören zu den wichtigsten Bauteilen der Wasserfassung. Ihre Aufgabe besteht darin, den Eintrag von groben Schwimmstoffen, Treibgut und Eis in das wassernutzende System zu verhindern. Infolge der Strömung durch den Rechen kommt es zu örtlichen Energieverlusten, die es zu berücksichtigen gilt. Im Zuge von 3D-numerischen Berechnungen de...