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Dr. Roman Gabl
FloWave Ocean Energy Research Facility, The University of Edinburgh

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Research Keywords & Expertise

0 Hydraulic Structure Design and Management
0 Hydraulics of Renewable Energy Systems
0 Rans Model
0 Kaplan
0 Velocity distribution

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Velocity distribution
hydro power

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Journal article
Published: 30 August 2021 in Journal of Marine Science and Engineering
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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 MaRINET2 partners. Test campaigns were conducted at each facility to a common specification and test matrix, providing the unique opportunity for intercomparison between facilities and working practices. A nonproprietary hinged raft, with a nominal scale of 1:25, was tested under a set of 12 irregular sea states. This allowed for an assessment of power output, hinge angles, mooring loads, and six-degree-of-freedom motions. The key outcome to be concluded from the results is that the facilities performed consistently, with the majority of variation linked to differences in sea state calibration. A variation of 5–10 % in mean power was typical and was consistent with the variability observed in the measured significant wave heights. The tank depth (which varied from 2–5 m) showed remarkably little influence on the results, although it is noted that these tests used an aerial mooring system with the geometry unaffected by the tank depth. Similar good agreement was seen in the heave, surge, pitch and hinge angle responses. In order to maintain and improve the consistency across laboratories, we make recommendations on characterising and calibrating the tank environment and stress the importance of the device–facility physical interface (the aerial mooring in this case).

ACS Style

Thomas Davey; Javier Sarmiento; Jérémy Ohana; Florent Thiebaut; Sylvain Haquin; Matthieu Weber; Sebastien Gueydon; Frances Judge; Eoin Lyden; Michael O’Shea; Roman Gabl; Laura-Beth Jordan; Martyn Hann; Daming Wang; Keri Collins; Daniel Conley; Deborah Greaves; David M. Ingram; Jimmy Murphy. Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter. Journal of Marine Science and Engineering 2021, 9, 946 .

AMA Style

Thomas Davey, Javier Sarmiento, Jérémy Ohana, Florent Thiebaut, Sylvain Haquin, Matthieu Weber, Sebastien Gueydon, Frances Judge, Eoin Lyden, Michael O’Shea, Roman Gabl, Laura-Beth Jordan, Martyn Hann, Daming Wang, Keri Collins, Daniel Conley, Deborah Greaves, David M. Ingram, Jimmy Murphy. Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter. Journal of Marine Science and Engineering. 2021; 9 (9):946.

Chicago/Turabian Style

Thomas Davey; Javier Sarmiento; Jérémy Ohana; Florent Thiebaut; Sylvain Haquin; Matthieu Weber; Sebastien Gueydon; Frances Judge; Eoin Lyden; Michael O’Shea; Roman Gabl; Laura-Beth Jordan; Martyn Hann; Daming Wang; Keri Collins; Daniel Conley; Deborah Greaves; David M. Ingram; Jimmy Murphy. 2021. "Round Robin Testing: Exploring Experimental Uncertainties through a Multifacility Comparison of a Hinged Raft Wave Energy Converter." Journal of Marine Science and Engineering 9, no. 9: 946.

Journal article
Published: 17 August 2021 in Water
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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 and ensure a long lasting life extension. This paper presents the concept of the submerged wall as a local high point in the headrace tunnel, which can—in combination with the intake gates—replace existing penstock shutoff valves. Such a replacement was conducted for the hydropower plant Schneiderau in Austria, which also allowed us to prove the concept based on measurements including a simulated break of the penstock. The presented solution can help to reduce investment costs and also minimise maintenance efforts and therefore is an attractive option for classic penstock shutoff valves for comparable projects.

ACS Style

Roman Gabl; Markus Wippersberger; Jakob Seibl; Christian Kröner; Bernhard Gems. Submerged Wall Instead of a Penstock Shutoff Valve—Alternative Protection as Part of a Refurbishment. Water 2021, 13, 2247 .

AMA Style

Roman Gabl, Markus Wippersberger, Jakob Seibl, Christian Kröner, Bernhard Gems. Submerged Wall Instead of a Penstock Shutoff Valve—Alternative Protection as Part of a Refurbishment. Water. 2021; 13 (16):2247.

Chicago/Turabian Style

Roman Gabl; Markus Wippersberger; Jakob Seibl; Christian Kröner; Bernhard Gems. 2021. "Submerged Wall Instead of a Penstock Shutoff Valve—Alternative Protection as Part of a Refurbishment." Water 13, no. 16: 2247.

Journal article
Published: 10 June 2021 in Ocean Engineering
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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), in the mid depth of the FloWave wave and current test tank. This experimental set-up allowed the measurement of the forces under realistic flow around the ROV without introducing significant interference. The paper presents the analysis of the load cell data as forces and moments in relation to the observed motion and rotation of the ROV. In addition to active propelled cases, a variation of current speed (up to 1 m/s) coming out of the four directions as well as different regular waves were tested. Three different distances of a cylindrical obstacle provided a quantification of the effect of flow shadowing from a structure in front of the ROV. The results can also be used as a validation experiment to expand the application of ROVs and the influence of obstacles based on numerical simulations.

ACS Style

Roman Gabl; Thomas Davey; Yu Cao; Qian Li; Boyang Li; Kyle L. Walker; Francesco Giorgio-Serchi; Simona Aracri; Aristides Kiprakis; Adam A. Stokes; David M. Ingram. Hydrodynamic loads on a restrained ROV under waves and current. Ocean Engineering 2021, 234, 109279 .

AMA Style

Roman Gabl, Thomas Davey, Yu Cao, Qian Li, Boyang Li, Kyle L. Walker, Francesco Giorgio-Serchi, Simona Aracri, Aristides Kiprakis, Adam A. Stokes, David M. Ingram. Hydrodynamic loads on a restrained ROV under waves and current. Ocean Engineering. 2021; 234 ():109279.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; Yu Cao; Qian Li; Boyang Li; Kyle L. Walker; Francesco Giorgio-Serchi; Simona Aracri; Aristides Kiprakis; Adam A. Stokes; David M. Ingram. 2021. "Hydrodynamic loads on a restrained ROV under waves and current." Ocean Engineering 234, no. : 109279.

Journal article
Published: 09 June 2021 in Applied Sciences
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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 theoretical (ideal) values of the centre of gravity (CG) and moment of inertia (MI). The building process of a scaled model results very often in a requested simplification of certain parts, which can influence the CG and also the MI of the scaled model. Knowing those discrepancies allows us to improve the comparability of both approaches but the measurement of those values is connected with either a higher uncertainty or a high level of effort. A significant improvement of such measurements can be reached by the deployment of a specific experimental set-up. This paper presents the classification of the newly designed swing with a high accuracy inertial inclinometer, which was verified by the marker-based motion capturing system. The achieved experiences are useful for the future use of the set-up as well as similar investigations. The comparison with the theoretical values for the swing as well as an example model showed very good agreements and a high accuracy of few millimetres for the CG and an error smaller 1% for MI.

ACS Style

Roman Gabl; Thomas Davey; Nixon; David Ingram. Accuracy Analysis of the Measurement of Centre of Gravity and Moment of Inertia with a Swing. Applied Sciences 2021, 11, 5345 .

AMA Style

Roman Gabl, Thomas Davey, Nixon, David Ingram. Accuracy Analysis of the Measurement of Centre of Gravity and Moment of Inertia with a Swing. Applied Sciences. 2021; 11 (12):5345.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; Nixon; David Ingram. 2021. "Accuracy Analysis of the Measurement of Centre of Gravity and Moment of Inertia with a Swing." Applied Sciences 11, no. 12: 5345.

Journal article
Published: 27 April 2021 in IEEE Robotics and Automation Letters
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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 evolution of hydrodynamic forces acting on a vehicle is required. To this end, we perform experiments in a wave tank with an ROV to validate the use of Linear Wave Theory (LWT) to capture the time history of surge, heave and pitch wave induced forces and moments. Validation is performed for various sea states, reconstructed with a mean correlation of 0.9138 in comparison to experimental measurements, displaying a maximum normalised mean error deviation between simulation and experimental data of 0.16 and 0.27 respectively for surge and heave forces, and 0.34 for pitch moment. The effectiveness of employing real-time wave disturbance forecasting for the purpose of anticipatory control is then assessed by incorporating the predicted loads within a Model Predictive Controller. Results display a mean RMS positional error reduction of 47.32% in comparison to a standard PD controller. This presents evidence that accurate, near real-time predictions of the wave-generated forces and moments on an ROV can be produced, laying the foundation for developing model-based predictive control strategies that better suit operation in harsh environments.

ACS Style

Kyle Liam Walker; Roman Gabl; Simona Aracri; Yu Cao; Adam Andrew Stokes; Aristides Kiprakis; Francesco Giorgio-Serchi. Experimental Validation of Wave Induced Disturbances for Predictive Station Keeping of a Remotely Operated Vehicle. IEEE Robotics and Automation Letters 2021, 6, 1 -1.

AMA Style

Kyle Liam Walker, Roman Gabl, Simona Aracri, Yu Cao, Adam Andrew Stokes, Aristides Kiprakis, Francesco Giorgio-Serchi. Experimental Validation of Wave Induced Disturbances for Predictive Station Keeping of a Remotely Operated Vehicle. IEEE Robotics and Automation Letters. 2021; 6 (3):1-1.

Chicago/Turabian Style

Kyle Liam Walker; Roman Gabl; Simona Aracri; Yu Cao; Adam Andrew Stokes; Aristides Kiprakis; Francesco Giorgio-Serchi. 2021. "Experimental Validation of Wave Induced Disturbances for Predictive Station Keeping of a Remotely Operated Vehicle." IEEE Robotics and Automation Letters 6, no. 3: 1-1.

Journal article
Published: 03 April 2021 in Journal of Global Health
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This rapid evidence review identifies and integrates evidence from epidemiology, microbiology and fluid dynamics on the transmission of SARS-CoV-2 in indoor environments. Searches were conducted in May 2020 in PubMed, medRxiv, arXiv, Scopus, WHO COVID-19 database, Compendex & Inspec. We included studies reporting data on any indoor setting except schools, any indoor activities and any potential means of transmission. Articles were screened by a single reviewer, with rejections assessed by a second reviewer. We used Joanna Briggs Institute and Critical Appraisal Skills Programme tools for evaluating epidemiological studies and developed bespoke tools for the evaluation of study types not covered by these instruments. Data extraction and quality assessment were conducted by a single reviewer. We conducted a meta-analysis of secondary attack rates in household transmission. Otherwise, data were synthesised narratively. We identified 1573 unique articles. After screening and quality assessment, fifty-eight articles were retained for analysis. Experimental evidence from fluid mechanics and microbiological studies demonstrates that aerosolised transmission is theoretically possible; however, we found no conclusive epidemiological evidence of this occurring. The evidence suggests that ventilation systems have the potential to decrease virus transmission near the source through dilution but to increase transmission further away from the source through dispersal. We found no evidence for faecal-oral transmission. Laboratory studies suggest that the virus survives for longer on smooth surfaces and at lower temperatures. Environmental sampling studies have recovered small amounts of viral RNA from a wide range of frequently touched objects and surfaces; however, epidemiological studies are inconclusive on the extent of fomite transmission. We found many examples of transmission in settings characterised by close and prolonged indoor contact. We estimate a pooled secondary attack rate within households of 11% (95% confidence interval (CI) = 9, 13). There were insufficient data to evaluate the transmission risks associated with specific activities. Workplace challenges related to poverty warrant further investigation as potential risk factors for workplace transmission. Fluid mechanics evidence on the physical properties of droplets generated by coughing, speaking and breathing reinforce the importance of maintaining 2 m social distance to reduce droplet transmission. This review provides a snap-shot of evidence on the transmission of SARS-CoV-2 in indoor environments from the early months of the pandemic. The overall quality of the evidence was low. As the quality and quantity of available evidence grows, it will be possible to reach firmer conclusions on the risk factors for and mechanisms of indoor transmission.

ACS Style

Lara Goodwin; Toneka Hayward; Prerna Krishan; Gemma Nolan; Madhurima Nundy; Kayla Ostrishko; Antonio Attili; Salva Barranco Cárceles; Emmanuel I Epelle; Roman Gabl; Evanthia J Pappa; Mateusz Stajuda; Simone Zen; Marshall Dozier; Niall Anderson; Ignazio M Viola; Ruth McQuillan. Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review. Journal of Global Health 2021, 11, 1 .

AMA Style

Lara Goodwin, Toneka Hayward, Prerna Krishan, Gemma Nolan, Madhurima Nundy, Kayla Ostrishko, Antonio Attili, Salva Barranco Cárceles, Emmanuel I Epelle, Roman Gabl, Evanthia J Pappa, Mateusz Stajuda, Simone Zen, Marshall Dozier, Niall Anderson, Ignazio M Viola, Ruth McQuillan. Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review. Journal of Global Health. 2021; 11 ():1.

Chicago/Turabian Style

Lara Goodwin; Toneka Hayward; Prerna Krishan; Gemma Nolan; Madhurima Nundy; Kayla Ostrishko; Antonio Attili; Salva Barranco Cárceles; Emmanuel I Epelle; Roman Gabl; Evanthia J Pappa; Mateusz Stajuda; Simone Zen; Marshall Dozier; Niall Anderson; Ignazio M Viola; Ruth McQuillan. 2021. "Which factors influence the extent of indoor transmission of SARS-CoV-2? A rapid evidence review." Journal of Global Health 11, no. : 1.

Journal article
Published: 20 January 2021 in IEEE Open Journal of Engineering in Medicine and Biology
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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 person while quietly and heavily breathing, while coughing, and with different face covers. Results: we found that all face covers without an outlet valve reduce the front flow through by at least 63% and perhaps as high as 86% if the unfiltered cough jet distance was resolved to the anticipated maximum distance of 2-3 m. However, surgical and handmade masks, and face shields, generate significant leakage jets that may present major hazards. Conclusions: the effectiveness of the masks should mostly be considered based on the generation of secondary jets rather than on the ability to mitigate the front throughflow.

ACS Style

Ignazio Maria Viola; Brian Peterson; Gabriele Pisetta; Geethanjali Pavar; Hibbah Akhtar; Filippo Menoloascina; Enzo Mangano; Katherine Elizabeth Dunn; Roman Gabl; Alex Nila; Emanuela Molinari; Cathal Cummins; Gerard Thompson; Tsz-Yan Milly Lo; Fiona C. Denison; Paul Digard; Omair Malik; Mark J. G. Dunn; Catherine M. McDougall; Felicity Mehendale. Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk. IEEE Open Journal of Engineering in Medicine and Biology 2021, 2, 26 -35.

AMA Style

Ignazio Maria Viola, Brian Peterson, Gabriele Pisetta, Geethanjali Pavar, Hibbah Akhtar, Filippo Menoloascina, Enzo Mangano, Katherine Elizabeth Dunn, Roman Gabl, Alex Nila, Emanuela Molinari, Cathal Cummins, Gerard Thompson, Tsz-Yan Milly Lo, Fiona C. Denison, Paul Digard, Omair Malik, Mark J. G. Dunn, Catherine M. McDougall, Felicity Mehendale. Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk. IEEE Open Journal of Engineering in Medicine and Biology. 2021; 2 ():26-35.

Chicago/Turabian Style

Ignazio Maria Viola; Brian Peterson; Gabriele Pisetta; Geethanjali Pavar; Hibbah Akhtar; Filippo Menoloascina; Enzo Mangano; Katherine Elizabeth Dunn; Roman Gabl; Alex Nila; Emanuela Molinari; Cathal Cummins; Gerard Thompson; Tsz-Yan Milly Lo; Fiona C. Denison; Paul Digard; Omair Malik; Mark J. G. Dunn; Catherine M. McDougall; Felicity Mehendale. 2021. "Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk." IEEE Open Journal of Engineering in Medicine and Biology 2, no. : 26-35.

Journal article
Published: 06 August 2020 in Water
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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 challenging to model, both physically and numerically, and there is a notable lack of reference data sets and studies to support the validation of this work. Most of the existing information is highly specific to certain hulls forms, or is limited to small motions. A previous study addressed this by modelling a floating cylinder (giving a more generic case) with roll and pitch motions in excess of 20∘. The presented experiment expands on that work to further investigate the previously observed switch between pitch and roll in the cylinder under wave action as induced by the sloshing of the internal water volume. An additional experimental investigation, focused on a single draft, was conducted to test open research questions from the previous study. Here we show that the roll response of the water filled cylinder is repeatable, independent of the tank position and wave amplitude, provided the observation time is long enough to capture the fully developed motion response of the floating object. The mooring system used comprised four soft lines connected on two points on the cylinder. This arrangement resulted in slightly different restoring forces in different wave directions. A relative change of the wave direction by 90∘ led to a larger wave frequency band in which the roll motion occurred. These cases were, again, also conducted with the solid ballast. Both sets of data provide an interesting validation case for future work on water ballast inside a floating object.

ACS Style

Roman Gabl; Thomas Davey; David M. Ingram. Roll Motion of a Water Filled Floating Cylinder—Additional Experimental Verification. Water 2020, 12, 2219 .

AMA Style

Roman Gabl, Thomas Davey, David M. Ingram. Roll Motion of a Water Filled Floating Cylinder—Additional Experimental Verification. Water. 2020; 12 (8):2219.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; David M. Ingram. 2020. "Roll Motion of a Water Filled Floating Cylinder—Additional Experimental Verification." Water 12, no. 8: 2219.

Journal article
Published: 01 August 2020 in Physics of Fluids
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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 go further than a specific distance, which we determine analytically, from the source before getting pulled into the sink. Larger droplets can travel further from the source before getting pulled into the sink by virtue of their larger inertia, and their maximum traveled distance is determined analytically. We investigate the effects of gravity, and we find that there are three distinct droplet behaviors categorized by their relative sizes: small, intermediate-sized, and large. Counterintuitively, we find that the droplets with a minimum horizontal range are neither small nor large, but of intermediate size. Furthermore, we show that in conditions of regular human respiration, these intermediate-sized droplets range in size from a few μm to a few hundred μm. The result that such droplets have a very short range could have important implications for the interpretation of existing data on droplet dispersion.

ACS Style

C. P. Cummins; O. J. Ajayi; F. V. Mehendale; R. Gabl; I. M. Viola. The dispersion of spherical droplets in source–sink flows and their relevance to the COVID-19 pandemic. Physics of Fluids 2020, 32, 083302 .

AMA Style

C. P. Cummins, O. J. Ajayi, F. V. Mehendale, R. Gabl, I. M. Viola. The dispersion of spherical droplets in source–sink flows and their relevance to the COVID-19 pandemic. Physics of Fluids. 2020; 32 (8):083302.

Chicago/Turabian Style

C. P. Cummins; O. J. Ajayi; F. V. Mehendale; R. Gabl; I. M. Viola. 2020. "The dispersion of spherical droplets in source–sink flows and their relevance to the COVID-19 pandemic." Physics of Fluids 32, no. 8: 083302.

Data descriptor
Published: 14 July 2020 in Data
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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 instruments. Simultaneous multi-point measurements of velocity along the horizontal tank profile from Single-Beam Acoustic Doppler Profiler (SB-ADP) were compared against multiple co-located point measurements from an ADV. Measurements were performed in the FloWave Ocean Energy Research Facility at the University of Edinburgh at flow velocities between 0.6 ms − 1 and 1.2 ms − 1 . This paper describes the data; the analysis of the inter-instrument comparison is presented in an associated Sensors paper by the same authors. This data-set contains (a) time series of raw SB-ADP uni-directional velocity measurements along a 10 m tank profile binned into 54 measurements cells and (b) ADV point measurements of three-directional velocity time series recorded in beam coordinates at selected locations along the profile. Associated with the data are instrument generated quality data, metadata and user-derived quality flags. An analysis of the quality of SB-ADP data along the profile is presented. This data-set provides multiple contemporaneous velocity measurements along the tank profile, relevant for correlation statistics, length-scale calculations and validation of numerical models simulating flow hydrodynamics in circular test facilities.

ACS Style

Marilou Jourdain De Thieulloy; Mairi Dorward; Chris Old; Roman Gabl; Thomas Davey; David M. Ingram; Brian G. Sellar. Single-Beam Acoustic Doppler Profiler and Co-Located Acoustic Doppler Velocimeter Flow Velocity Data. Data 2020, 5, 61 .

AMA Style

Marilou Jourdain De Thieulloy, Mairi Dorward, Chris Old, Roman Gabl, Thomas Davey, David M. Ingram, Brian G. Sellar. Single-Beam Acoustic Doppler Profiler and Co-Located Acoustic Doppler Velocimeter Flow Velocity Data. Data. 2020; 5 (3):61.

Chicago/Turabian Style

Marilou Jourdain De Thieulloy; Mairi Dorward; Chris Old; Roman Gabl; Thomas Davey; David M. Ingram; Brian G. Sellar. 2020. "Single-Beam Acoustic Doppler Profiler and Co-Located Acoustic Doppler Velocimeter Flow Velocity Data." Data 5, no. 3: 61.

Journal article
Published: 12 July 2020 in Sensors
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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-scaled open ocean environment, and it is a key step in gaining this understanding. Knowledge of the hydrodynamic conditions during tests is critical and measurements at multiple locations are required to accurately characterise spatially varying flow in test tank facilities. The paper presents a laboratory technique using an acoustic velocimetry instrument, the range over-which measurements are acquired being more akin to open water applications. This enables almost simultaneous multi-point measurements of uni-directional velocity along a horizontal profile. Velocity measurements have been obtained from a horizontally mounted Single Beam Acoustic Doppler (SB-ADP) profiler deployed in the FloWave Ocean Energy Research Facility at the University of Edinburgh. These measurements have been statistically compared with point measurements obtained while using a co-located Acoustic Doppler Velocimeter (ADV). Measurements were made with both instruments under flow velocities varying from 0.6 ms−1 to 1.2 ms−1, showing that flow higher than 1 ms−1 was more suitable. Using a SB-ADP has shown the advantage of gaining 54 simultaneous measurement points of uni-directional velocity, covering a significant area with a total distance of 10 m of the test-tank, at a measurement frequency of 16 Hz. Of those measurement points, 41 were compared with co-located ADV measurements covering 8 m of the profile for a tank nominal flow velocity of 0.8 ms−1, and four distributed locations were chosen to to carry out the study at 0.6 ms−1, 1.0 ms−1, and 1.2 ms−1. The comparison with the ADV measurement showed a 2% relative bias on average.

ACS Style

Marilou Jourdain De Thieulloy; Mairi Dorward; Chris Old; Roman Gabl; Thomas Davey; David M. Ingram; Brian G. Sellar. On the Use of a Single Beam Acoustic Current Profiler for Multi-Point Velocity Measurement in a Wave and Current Basin. Sensors 2020, 20, 3881 .

AMA Style

Marilou Jourdain De Thieulloy, Mairi Dorward, Chris Old, Roman Gabl, Thomas Davey, David M. Ingram, Brian G. Sellar. On the Use of a Single Beam Acoustic Current Profiler for Multi-Point Velocity Measurement in a Wave and Current Basin. Sensors. 2020; 20 (14):3881.

Chicago/Turabian Style

Marilou Jourdain De Thieulloy; Mairi Dorward; Chris Old; Roman Gabl; Thomas Davey; David M. Ingram; Brian G. Sellar. 2020. "On the Use of a Single Beam Acoustic Current Profiler for Multi-Point Velocity Measurement in a Wave and Current Basin." Sensors 20, no. 14: 3881.

Data descriptor
Published: 30 June 2020 in Data
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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 different distances of a simplified cylindrical obstacle (shading effects) were investigated in addition to the free stream cases. Eight tethers held the ROV in the middle of the 2 m water depth to minimise the influence of the support structure without completely restricting the degrees of freedom (DoF). Each tether was equipped with a load cell and small motions and rotations were documented with an underwater video motion capture system. The paper describes the experimental set-up, input values (current speed and wave definitions) and initial processing of the data. In addition to the raw data, a processed dataset is provided, which includes forces in all three main coordinate directions for each mounting point synchronised with the 6DoF results and the free surface elevations. The provided dataset can be used as a validation experiment as well as for testing and development of an algorithm for position control of comparable ROVs.

ACS Style

Roman Gabl; Thomas Davey; Yu Cao; Qian Li; Boyang Li; Kyle L. Walker; Francesco Giorgio-Serchi; Simona Aracri; Aristides Kiprakis; Adam A. Stokes; David M. Ingram. Experimental Force Data of a Restrained ROV under Waves and Current. Data 2020, 5, 57 .

AMA Style

Roman Gabl, Thomas Davey, Yu Cao, Qian Li, Boyang Li, Kyle L. Walker, Francesco Giorgio-Serchi, Simona Aracri, Aristides Kiprakis, Adam A. Stokes, David M. Ingram. Experimental Force Data of a Restrained ROV under Waves and Current. Data. 2020; 5 (3):57.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; Yu Cao; Qian Li; Boyang Li; Kyle L. Walker; Francesco Giorgio-Serchi; Simona Aracri; Aristides Kiprakis; Adam A. Stokes; David M. Ingram. 2020. "Experimental Force Data of a Restrained ROV under Waves and Current." Data 5, no. 3: 57.

Journal article
Published: 25 June 2020 in Coastal Engineering
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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 experiments conducted in a 50 m × 50 m large basin at constant water depth h. The experiments involved five iceberg calving mechanisms: A: capsizing, B: gravity-dominated fall, C: buoyancy-dominated fall, D: gravity-dominated overturning and E: buoyancy-dominated overturning. The kinematics of the up to 187 kg heavy plastic blocks mimicking icebergs was measured with a motion sensor and the wave profiles were recorded with wave probes at up to 35 locations. The IBTs from the gravity-dominated mechanisms (B and D) are roughly an order of magnitude larger than from mechanisms A, C and E. Empirical equations for preliminary hazard assessment and mitigation for the maximum wave height, amplitude and period for both the near- and far-field are derived for the five calving mechanisms individually and combined. The relative released energy, Froude number and relative iceberg width are the most influential dimensionless parameters in these equations. A maximum wave height decay trend close to (r/h)−1.0 is observed, with r as the radial distance, in agreement with the theoretical wave decay from a point source. The empirical equations are applied to a past event resulting in a good agreement and the upscaled wave periods to typical Greenlandic conditions overlap with the lower spectrum of landslide-tsunamis. However, empirical equations for landslide-tsunamis were found to be of limited use to predict IBTs in the far-field supporting the need of the newly introduced empirical equations for IBT hazard assessment and mitigation.

ACS Style

Valentin Heller; Tommaso Attili; Fan Chen; Roman Gabl; Guido Wolters. Large-scale investigation into iceberg-tsunamis generated by various iceberg calving mechanisms. Coastal Engineering 2020, 163, 103745 .

AMA Style

Valentin Heller, Tommaso Attili, Fan Chen, Roman Gabl, Guido Wolters. Large-scale investigation into iceberg-tsunamis generated by various iceberg calving mechanisms. Coastal Engineering. 2020; 163 ():103745.

Chicago/Turabian Style

Valentin Heller; Tommaso Attili; Fan Chen; Roman Gabl; Guido Wolters. 2020. "Large-scale investigation into iceberg-tsunamis generated by various iceberg calving mechanisms." Coastal Engineering 163, no. : 103745.

Journal article
Published: 05 December 2019 in Sensors
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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 the direction. For this purpose, two time of flight sensors are combined with a door sensor and a motion detection sensor (for redundancy) on one single side of the door frame. The period between two single measurements could be reduced to 50 ms, which allows the measurement of walking speed up to 2 ms − 1 . The accuracy of the time stamp for each event is less than one second and ensures a precise documentation of the consultation time. This paper presents the development of the sensor system, the miniaturisation of the installation and first measurement results, as well as the measurement’s concept of quality analysis, including multiple door applications. In future steps, the sensor system will be deployed at different medical practices to determine the exact duration of the patient–physician interaction over a longer time period.

ACS Style

Roman Gabl; Florian Stummer. Development of a Sensor to Measure Physician Consultation Times. Sensors 2019, 19, 5359 .

AMA Style

Roman Gabl, Florian Stummer. Development of a Sensor to Measure Physician Consultation Times. Sensors. 2019; 19 (24):5359.

Chicago/Turabian Style

Roman Gabl; Florian Stummer. 2019. "Development of a Sensor to Measure Physician Consultation Times." Sensors 19, no. 24: 5359.

Journal article
Published: 26 November 2019 in Water
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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 an open topped hollow cylinder ballasted to different displacements. Regular waves are used to excite the floating structure, which exhibits rotation angles of over 20 degrees and a heave motion double that of the wave amplitude. Four different drafts are investigated, each with two different ballast options: with (water) and without (solid) a free surface. The comparison shows a small difference in the body’s three translational motions as well as the rotation around the normal axis to the water surface. Significant differences are observed in the rotation about the wave direction comparable to parametric rolling as seen in ships. The three bigger drafts with free surface switch the dominant global rotation direction from pitch to roll, which can clearly be attributed to the sloshing of the internal water. The presented study provides a new dataset and comparison of varying ballast types on device motions, which may be used for future validation experiments.

ACS Style

Roman Gabl; Thomas Davey; Nixon; Jeffrey Steynor; David M. Ingram. Comparison of a Floating Cylinder with Solid and Water Ballast. Water 2019, 11, 2487 .

AMA Style

Roman Gabl, Thomas Davey, Nixon, Jeffrey Steynor, David M. Ingram. Comparison of a Floating Cylinder with Solid and Water Ballast. Water. 2019; 11 (12):2487.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; Nixon; Jeffrey Steynor; David M. Ingram. 2019. "Comparison of a Floating Cylinder with Solid and Water Ballast." Water 11, no. 12: 2487.

Data descriptor
Published: 21 November 2019 in Data
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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. Additionally, the time series of the six-degree freedom response of the floating structure is made available. Regular waves with an initial amplitude of 0.05 m and frequencies over the range 0.3 to 1.1 Hz are investigated. This results in a wide range of different responses of the floating structure as well as very big rotations of up to 20 degrees. This dataset allows for identification of the influence caused by the sloshing of the interior water volume and can be used to validate numerical models of fluid–structure–fluid interaction.

ACS Style

Roman Gabl; Thomas Davey; Nixon; Jeffrey Steynor; David M. Ingram. Experimental Data of a Floating Cylinder in a Wave Tank: Comparison Solid and Water Ballast. Data 2019, 4, 146 .

AMA Style

Roman Gabl, Thomas Davey, Nixon, Jeffrey Steynor, David M. Ingram. Experimental Data of a Floating Cylinder in a Wave Tank: Comparison Solid and Water Ballast. Data. 2019; 4 (4):146.

Chicago/Turabian Style

Roman Gabl; Thomas Davey; Nixon; Jeffrey Steynor; David M. Ingram. 2019. "Experimental Data of a Floating Cylinder in a Wave Tank: Comparison Solid and Water Ballast." Data 4, no. 4: 146.

Journal article
Published: 21 May 2019 in Water
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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 arranged steel cables instead of bars. The presented study investigated experimentally the head loss coefficient of an angled horizontal trash rack with circular bars (CBTR) and the FFF with identical cross sections in a flume (scale 1:2). Nine configurations of different bar and cable spacing (blockage ratio) and rack angles were studied for CBTR and FFF considering six different stationary flow conditions. The results demonstrate that head loss coefficient is independent from the studied Bar–Reynolds number range and increases with increasing blockage ratio and angle. At an angle of 30 degrees, a direct comparison between the two different rack options was conducted to investigate the effect of cable vibrations. At the lowest blockage ratio, head loss for both options are in similar very low ranges, while the head loss coefficient of the FFF increases significantly compared to the CBTR with an increase of blockage. Further, the results indicate a moderate overestimation with the predicted head loss by common head loss equations developed for inclined vertical trash racks. Thus, an adaption of the design equation is proposed to improve the estimation of head loss on both rack options.

ACS Style

Heidi Böttcher; Roman Gabl; Markus Aufleger. Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables. Water 2019, 11, 1056 .

AMA Style

Heidi Böttcher, Roman Gabl, Markus Aufleger. Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables. Water. 2019; 11 (5):1056.

Chicago/Turabian Style

Heidi Böttcher; Roman Gabl; Markus Aufleger. 2019. "Experimental Hydraulic Investigation of Angled Fish Protection Systems—Comparison of Circular Bars and Cables." Water 11, no. 5: 1056.

Journal article
Published: 29 January 2019 in Scientific Reports
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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. Calving icebergs interact with the surrounding water through different mechanisms and we investigate five; A: capsizing, B: gravity-dominated fall, C: buoyancy-dominated fall, D: gravity-dominated overturning and E: buoyancy-dominated overturning. Gravity-dominated icebergs essentially fall into the water body whereas buoyancy-dominated icebergs rise to the water surface. We find with unique large-scale laboratory experiments that iceberg-tsunami heights from gravity-dominated mechanisms (B and D) are roughly an order of magnitude larger than from A, C and E. A theoretical model for released iceberg energy supports this finding and the measured wave periods upscaled to Greenlandic outlet glaciers agree with field observations. Whilst existing empirical equations for landslide-tsunamis establish estimates of an upper envelope of the maximum iceberg-tsunami heights, they fail to capture the physics of most iceberg-tsunami mechanisms.

ACS Style

Valentin Heller; Fan Chen; Markus Brühl; Roman Gabl; Xuexue Chen; Guido Wolters; Helge Fuchs. Large-scale experiments into the tsunamigenic potential of different iceberg calving mechanisms. Scientific Reports 2019, 9, 861 .

AMA Style

Valentin Heller, Fan Chen, Markus Brühl, Roman Gabl, Xuexue Chen, Guido Wolters, Helge Fuchs. Large-scale experiments into the tsunamigenic potential of different iceberg calving mechanisms. Scientific Reports. 2019; 9 (1):861.

Chicago/Turabian Style

Valentin Heller; Fan Chen; Markus Brühl; Roman Gabl; Xuexue Chen; Guido Wolters; Helge Fuchs. 2019. "Large-scale experiments into the tsunamigenic potential of different iceberg calving mechanisms." Scientific Reports 9, no. 1: 861.

Journal article
Published: 29 December 2018 in Water
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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 conventional measurement techniques, the sloshing of the internal free surface is more difficult to capture. The location of the internal free surface is normally extrapolated from measuring the pressure acting on the internal walls of the vessel. In order to understand better the loading mechanisms of sloshing internal fluids, a method of capturing the transient inner free surface motion with negligible affect on the response of the fluid or structure is required. In this paper two methods will be demonstrated for this purpose. The first approach uses resistive wave gauges made of copper tape to quantify the water run-up height on the walls of the structure. The second approach extends the conventional use of optical motion tracking to report the position of randomly distributed free floating markers on the internal water surface. The methods simultaneously report the position of the internal free surface with good agreement under static conditions, with absolute variation in the measured water level of around 4 mm. This new combined approach provides a map of the free surface elevation under transient conditions. The experimental error is shown to be acceptable (low mm-range), proving that these experimental techniques are robust free surface tracking methods in a range of situations.

ACS Style

Roman Gabl; Jeffrey Steynor; David I. M. Forehand; Thomas Davey; Tom Bruce; David M. Ingram. Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure. Water 2018, 11, 50 .

AMA Style

Roman Gabl, Jeffrey Steynor, David I. M. Forehand, Thomas Davey, Tom Bruce, David M. Ingram. Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure. Water. 2018; 11 (1):50.

Chicago/Turabian Style

Roman Gabl; Jeffrey Steynor; David I. M. Forehand; Thomas Davey; Tom Bruce; David M. Ingram. 2018. "Capturing the Motion of the Free Surface of a Fluid Stored within a Floating Structure." Water 11, no. 1: 50.

Journal article
Published: 10 August 2018 in Water
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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 structure are compared with numerical simulations (ANSYS-CFX) as well as with a scale model test (scale 1:20). The laboratory experiment substantially benefited from the preliminary numerical investigation in respect of the location and implementation of the model boundaries. In return was the confidence in the numerics strengthened by the successful validation of the local head loss and the velocity distribution for the main operation cases. This allowed that the main inputs for the structural design and the further optimisation is conducted only with the 3D-numerical tool. The paper presents the interlaced concept as well as the main finding of the investigation, which lead to a successful adaptation of the intake structure.

ACS Style

Roman Gabl; Bernhard Gems; Florian Birkner; Bernhard Hofer; Markus Aufleger. Adaptation of an Existing Intake Structure Caused by Increased Sediment Level. Water 2018, 10, 1066 .

AMA Style

Roman Gabl, Bernhard Gems, Florian Birkner, Bernhard Hofer, Markus Aufleger. Adaptation of an Existing Intake Structure Caused by Increased Sediment Level. Water. 2018; 10 (8):1066.

Chicago/Turabian Style

Roman Gabl; Bernhard Gems; Florian Birkner; Bernhard Hofer; Markus Aufleger. 2018. "Adaptation of an Existing Intake Structure Caused by Increased Sediment Level." Water 10, no. 8: 1066.