Richard Karsten | Acadia University (original) (raw)
Papers by Richard Karsten
Using Drifters Equipped with Acoustic Tags to Verify the Efficacy of an Array of Acoustic Receivers for Estimating Probability of Fish-Turbine Encounter
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 seconds were usually detected by the receiver array even in fast currents during spring tides but pulse position modulation tags were inade...
Journal of Fluid Mechanics, Jun 10, 2000
Baroclinic large-amplitude geostrophic (LAG) models, which assume a leading-order geostrophic bal... more Baroclinic large-amplitude geostrophic (LAG) models, which assume a leading-order geostrophic balance but allow for large-amplitude isopycnal deflections, provide a suitable framework to model the large-amplitude motions exhibited in frontal regions. The qualitative dynamical characterization of LAG models depends critically on the underlying length scale. If the length scale is sufficiently large, the effect of differential rotation, i.e. the β-effect, enters the dynamics at leading order. For smaller length scales, the β-effect, while non-negligible, does not enter the dynamics at leading order. These two dynamical limits are referred to as strong-β and weak-β models, respectively. A comprehensive description of the nonlinear dynamics associated with the strongβ models is given. In addition to establishing two new nonlinear stability theorems, we extend previous linear stability analyses to account for the finite-amplitude development of perturbed fronts. We determine whether the linear solutions are subject to nonlinear secondary instabilities and, in particular, a new long-wave-shortwave (LWSW) resonance, which is a possible source of rapid unstable growth at long length scales, is identified. The theoretical analyses are tested against numerical simulations. The simulations confirm the importance of the LWSW resonance in the development of the flow. Simulations show that instabilities associated with vanishing potentialvorticity gradients can develop into stable meanders, eddies or breaking waves. By examining models with different layer depths, we reveal how the dynamics associated with strong-β models qualitatively changes as the strength of the dynamic coupling between the barotropic and baroclinic motions varies.
The semi-diurnal tide in Hudson Strait as a resonant channel oscillation
Deep Blue (University of Michigan), 2010
... Patrick F. Cummins1,*, Richard H. Karsten2 and Brian K. Arbic3, ... Following the work of St... more ... Patrick F. Cummins1,*, Richard H. Karsten2 and Brian K. Arbic3, ... Following the work of St-Laurent (2006), a calcula-tion of the normal modes of the HB/HS system was presented and this indicated a resonant mode at a period of 12.3 h. A decay experiment with a global ...
A note on the stability theory of buoyancy-driven ocean currents over a sloping bottom
Zeitschrift für Angewandte Mathematik und Physik, 1996
Journal of Fluid Mechanics, Jun 10, 2000
This paper is a continuation of our study on nonlinear processes in large-amplitude geostrophic (... more This paper is a continuation of our study on nonlinear processes in large-amplitude geostrophic (LAG) dynamics. Here, we examine the so-called weak-β models. These models arise when the intrinsic length scale is large enough so that the dynamics is geostrophic to leading order but not so large that the β-effect enters into the dynamics at leading order (but remains, nevertheless, dynamically non-negligible). In contrast to our previous analysis of strong-β LAG models in Part 1, we show that the weak-β models allow for vigorous linear baroclinic instability. For two-layer weak-β LAG models in which the mean depths of both layers are approximately equal, the linear instability problem can exhibit an ultraviolet catastrophe. We argue that it is not possible to establish conditions for the nonlinear stability in the sense of Liapunov for a steady flow. We also show that the finite-amplitude evolution of a marginally unstable flow possesses explosively unstable modes, i.e. modes for which the amplitude becomes unbounded in finite time. Numerical simulations suggest that the development of large-amplitude meanders, squirts and eddies is correlated with the presence of these explosively unstable modes. For two-layer weak-β LAG models in which one of the two layers is substantially thinner than the other, the linear stability problem does not exhibit an ultraviolet catastrophe and it is possible to establish conditions for the nonlinear stability in the sense of Liapunov for steady flows. A finite-amplitude analysis for a marginally unstable flow suggests that nonlinearities act to stabilize eastward and enhance the instability of westward flows. Numerical simulations are presented to illustrate these processes.
Journal of Marine Science and Engineering, Aug 14, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Using Drifters Equipped with Acoustic Tags to Verify the Efficacy of an Array of Acoustic Receivers for Estimating Probability of Fish-Turbine Encounter
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 seconds were usually detected by the receiver array even in fast currents during spring tides but pulse position modulation tags were inadequate. Sometimes very few high residency tag signals were detected when fast tidal currents swept a drifter through the receiver array, so increasing the transmission interval degrades performance at the tidal energy development area. High residency tags suspended close to the sea surface were slightly less likely to be detected if they passed by during calm conditions. Previously measured detection efficiencies were found to slightly overestimate the chances of a high residency tag carried by a drifter being detected as it passed by a receiver. This works elucidates the effectiveness with which acoustically tagged fish are detected in fast, highly turbulent tidal currents and informs the application of detection efficiency measurements to calculate the probability that fish encounter a marine hydrokinetic turbine.
A unified asymptotic derivation of two-layer, frontal geostrophic models including planetary sphericity and variable topography
Physics of Fluids, Sep 1, 1999
Journal of Marine Science and Engineering
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources, but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and the detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 s were usually detected by the receiver array even in fast currents during spring tides but pulse-position modulation tags were inadeq...
Determining Marine Renewable Energy Areas in the Bay of Fundy
American Geophysical Union eBooks, Feb 1, 2016
Abstract: Assessment of tidal current energy in the Bay of Fundy
Tidal stream energy is a renewable energy resource that might be developed to offset carbon emiss... more Tidal stream energy is a renewable energy resource that might be developed to offset carbon emissions. A tidal energy demonstration (TED) area has been designated in Minas Passage, Bay of Fundy, for testing and installing marine hydrokinetic (MHK) turbines. Regulations require quantification of the potential for MHK turbine installations to harm local populations of marine animals. Here we use acoustic telemetry to quantify probability that post smolt Inner Bay of Fundy salmon encounter a turbine installation at the TED area. Previous work has quantified detection efficiency of Innovasea HR acoustic tags as a function of current speed and range from a moored HR2 receiver and also demonstrated that drifters carrying HR tags will be effectively detected when the drifter track crosses the array of HR2 receivers in Minas Passage. Salmon smolts were tagged and released in Gaspereau and Stewiacke Rivers, Nova Scotia, in order that the HR2 receiver array could monitor seaward migration of ...
For many expensive deterministic computer simulators, the outputs do not have replication error a... more For many expensive deterministic computer simulators, the outputs do not have replication error and the desired metamodel (or statistical emulator) is an interpolator of the observed data. Realizations of Gaussian spatial processes (GP) are commonly used to model such simulator outputs. Fitting a GP model to n data points requires the computation of the inverse and determinant of n × n correlation matrices, R, that are sometimes computationally unstable due to near-singularity of R. This happens if any pair of design points are very close together in the input space. The popular approach to overcome near-singularity is to introduce a small nugget (or jitter) parameter in the model that is estimated along with other model parameters. The inclusion of a nugget in the model often causes unnecessary over-smoothing of the data. In this paper, we propose a lower bound on the nugget that minimizes the over-smoothing and an iterative regularization approach to construct a predictor that further improves the interpolation accuracy. We also show that the proposed predictor converges to the GP interpolator.
The attempt to determine the population growth rate from field data reveals several ambiguities i... more The attempt to determine the population growth rate from field data reveals several ambiguities in its definition(s), which seem to throw into question the very concept itself. However, an alternative point of view is proposed that not only preserves the identity of the concept, but also helps discriminate between competing models for capturing the data.
Validating a New Marine Forecasting Tool for Tidal Energy in Grand Passage, Bay of Fundy
Turbulent flow mapping in a high-flow tidal channel using mobile acoustic Doppler current profilers
Renewable Energy, 2021
Abstract In this investigation, instrumented mobile platforms are used to spatially map the turbu... more Abstract In this investigation, instrumented mobile platforms are used to spatially map the turbulent flows in Grand Passage, one of the Bay of Fundy's more energetic tidal channels in Nova Scotia, Canada. The aim is to characterize the flow around the PLAT-I floating tidal energy platform developed by Sustainable Marine Energy Canada (SMEC). GPS-tracked surface drifters equipped with fast-sampling acoustic Doppler current profilers (ADCPs) provide turbulence-resolving vertical profiles of velocity and turbulent kinetic energy dissipation rate along drifter trajectories, while vessel-mounted ADCP transects complement the mean flow velocity measurements. These data are used to construct tridimensional quasi-synoptic maps of mean velocities and turbulence parameters for several stages of the tide around PLAT-I's location including peak ebb and flood currents. The data set includes measurements under natural flow conditions, and while the turbines installed on PLAT-I were both not operational and operational. The measurement techniques and resulting maps successfully capture the spatial and temporal structure of the flow for unsteady conditions for various tidal conditions. The combined wake of the four 6.3 m operational PLAT-I turbines was measured for a single tidal stage. Closer to the turbines, the vertical extent of the wake is about 6 m (approximately one turbine diameter), increasing with distance downstream, while the maximum observed velocity deficit is 26% relative to not operating conditions, decreasing with distance downstream.
Journal of Fish Biology, 2018
Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45 ∘ ... more Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45 ∘ 20 ′ N; 64 ∘ 00 ′ W) and the Bay of Fundy with pop-up satellite archival tags (MiniPAT) measuring physical variables (pressure, temperature, light). Of six tags deployed during June and July, five provided pop-up locations and two were recovered after c. 4 months. Analysis of recovered archival data revealed that the frequency of surfacing events was highest (78•9%) when A. oxyrinchus were in Minas Basin at depths <10 m. Surfacing frequency decreased substantially when fish migrated into greater depths of the Bay of Fundy (>40 m). The tidal cycle in Minas Basin had a significant relationship to surfacing frequency, with the most surfacing events (49•5%) occurring on the flood tide, from mid-to high-tide. Surfacing events ranged from 0-12 a day and the maximum number occurred between 2300 and 0300 hours. Maximum surfacing ascent speeds ranged from 0•50 to 4•17 m s −1 and maximum descent speeds ranged from 0•17 to 3•17 m s −1. Buoyancy control, by gulping air to inflate the gas bladder, is proposed as the main reason for surfacing behaviour in A. oxyrinchus.
Ocean Engineering, 2017
This paper specifically focuses on site-specific CFD modelling in the context of tidal energy dev... more This paper specifically focuses on site-specific CFD modelling in the context of tidal energy development, and presents results for two sites from the Fundy Tidal Region (FTR) situated in Eastern Canada. The FTR is one of the best and most energetic areas in the world for tidal energy development. To efficiently meet the computational demands of modelling unsteady three-dimensional turbulent flow in complex tidal zone terrains, highly parallel GPU hardware are utilized. Strategically deployed Acoustic Doppler Current Profiler (ADCP) measurements at two tidal turbine locations provide validation of the predictions under ebb and flood flows. The processing methodology of ADCP devices is incorporated into the CFD simulation to improve predicted turbulence levels for validation. The simulations use detached eddy simulation (DES) turbulence modelling with engineered inlet boundary conditions and realistic bathymetry. The inlet boundaries use mean horizontal velocity values interpolated from regional tidal simulations and are perturbed by synthetic turbulence to accelerate boundary layer development. Simulations cover tidal developments from~1.5 to 3 square kilometres with spatial and temporal resolutions of 1-2 m and 0.1 s, respectively.
Journal of Physical Oceanography, 1995
This report presents an update on the extractable power potential of tidal currents in a number o... more This report presents an update on the extractable power potential of tidal currents in a number of passages around Nova Scotia. Since initial reports by EPRI [1] and the Triton [2] were produced, we have gained a better understanding of how the extraction of power from tidal currents affect the tidal system. This report uses numerical simulations and theoretical calculations to predict not only the power that can be extracted but also the resulting reduction in flow through the passage. As such, it gives power estimates along with a first measure of the environmental impact of extracting tidal energy from the system. In particular, the new power estimates are considerably higher for two passages, Minas Channel and Digby Gut, while the estimates for other passages are similar to previous results. Overall, we estimate potential power extraction of 2000 MW in the Minas Channel, 50 to 100 MW in the Digby Neck region and 1 to 2 MW in Cape Breton. In Minas Channel, the mean extractable power is estimated to be 7200 MW, of which 3500 MW can be extracted with a 10% reduction in flow through the channel and 2000 MW can be extracted with a 5% reduction in flow. It should be stressed that Minas Channel, which includes Minas Passage, forms one tidal system with Minas Basin, that is, it is one source of energy and one system that will be changed if energy is extracted. The extractable power from Minas Channel is a reflection of the potential energy in the world's highest tides of the Minas Basin. A reduction in flow through Minas Channel will result in a corresponding reduction in the tides in Minas Basin. This will have important impacts on the intertidal regions that surround the basin. As such, we suggest the 2000 MW power estimate, which limits the reduction in flow to 5%, is the best estimate for the power potential of the Minas Channel region. Finally, it should be noted that the highest water speeds, and thus, highest power densities are found in Minas Passage. As such, it is Minas Passage that has the greatest potential for the development of commercial-scale, tidal turbine arrays. The passages of the Digby Neck region offer the potential of significant tidal power. In particular, the Digby Gut/Annapolis Basin system has a much larger potential than previously estimated. The mean extractable power is 180 MW, of which 67 MW can be extracted with only a 5% reduction in the flow through Digby Gut. However, this estimate comes with the caveat that the flow speed and power densities in Digby Gut are low. Realizing a significant portion of the potential power will require technology that can extract power from flows with speeds of 1 to 2 m/s. On the other hand, Petit and Grand Passages have higher velocities and power densities-similar to those found in Minas Passage. However, these passages lie between two large, open bodies of water. The flow through these small passages is not important in determining the tides in these waters. As such, they only have moderate potential power extraction-33 MW for Petit Passage and 16 MW for Grand Passage. But, it is expected that a reduction in flow through these passages will have a small impact on the surrounding tides. Therefore, Richard H. Karsten 2 power extraction that reduces the flow by 10% (or possibly higher) could be acceptable giving power estimates of 19 MW for Petit Passage and 8.9 MW for Grand Passage. The passages of the Bra D'Or Lakes have a small potential for power extraction-4.6 MW for Great Bra D'Or Channel and 2.2 MW for Barra Strait. The water exchange between the Bra D'Or Lakes and the ocean is a complicated process that supports the ecology of the region. Any power extraction of power should minimize the changes to these exchanges, and therefore we suggest the change in flow through the passages be limited to a 5% reduction, giving power estimates of 1.1 MW for Great Bra D'Or Channel and 0.6 MW for Barra Strait. At this point, we have examined no other sites in Nova Scotia that have the strong tidal currents in a region suitable for large scale tidal power extraction. Ongoing research along the South West Nova Scotia coastline has identified locations suitable for community scale tidal development. These will be reported on in a later report. Finally, estimating the portion of extracted energy that can be converted into useable electricity supplied to the grid is a difficult process. Tidal energy technology is still under development and changes in turbine technology and the design of turbine arrays will affect how much power can be generated. For this report, we only use a very basic model to estimate that 40% of the extractable power can be converted into electricity. We also estimate that the installed capacity necessary to generate this power to be 70% the extractable power. Therefore, the estimated mean extractable power are moderate overestimates of the potential installed capacity of turbine arrays for each passage.
Using Drifters Equipped with Acoustic Tags to Verify the Efficacy of an Array of Acoustic Receivers for Estimating Probability of Fish-Turbine Encounter
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 seconds were usually detected by the receiver array even in fast currents during spring tides but pulse position modulation tags were inade...
Journal of Fluid Mechanics, Jun 10, 2000
Baroclinic large-amplitude geostrophic (LAG) models, which assume a leading-order geostrophic bal... more Baroclinic large-amplitude geostrophic (LAG) models, which assume a leading-order geostrophic balance but allow for large-amplitude isopycnal deflections, provide a suitable framework to model the large-amplitude motions exhibited in frontal regions. The qualitative dynamical characterization of LAG models depends critically on the underlying length scale. If the length scale is sufficiently large, the effect of differential rotation, i.e. the β-effect, enters the dynamics at leading order. For smaller length scales, the β-effect, while non-negligible, does not enter the dynamics at leading order. These two dynamical limits are referred to as strong-β and weak-β models, respectively. A comprehensive description of the nonlinear dynamics associated with the strongβ models is given. In addition to establishing two new nonlinear stability theorems, we extend previous linear stability analyses to account for the finite-amplitude development of perturbed fronts. We determine whether the linear solutions are subject to nonlinear secondary instabilities and, in particular, a new long-wave-shortwave (LWSW) resonance, which is a possible source of rapid unstable growth at long length scales, is identified. The theoretical analyses are tested against numerical simulations. The simulations confirm the importance of the LWSW resonance in the development of the flow. Simulations show that instabilities associated with vanishing potentialvorticity gradients can develop into stable meanders, eddies or breaking waves. By examining models with different layer depths, we reveal how the dynamics associated with strong-β models qualitatively changes as the strength of the dynamic coupling between the barotropic and baroclinic motions varies.
The semi-diurnal tide in Hudson Strait as a resonant channel oscillation
Deep Blue (University of Michigan), 2010
... Patrick F. Cummins1,*, Richard H. Karsten2 and Brian K. Arbic3, ... Following the work of St... more ... Patrick F. Cummins1,*, Richard H. Karsten2 and Brian K. Arbic3, ... Following the work of St-Laurent (2006), a calcula-tion of the normal modes of the HB/HS system was presented and this indicated a resonant mode at a period of 12.3 h. A decay experiment with a global ...
A note on the stability theory of buoyancy-driven ocean currents over a sloping bottom
Zeitschrift für Angewandte Mathematik und Physik, 1996
Journal of Fluid Mechanics, Jun 10, 2000
This paper is a continuation of our study on nonlinear processes in large-amplitude geostrophic (... more This paper is a continuation of our study on nonlinear processes in large-amplitude geostrophic (LAG) dynamics. Here, we examine the so-called weak-β models. These models arise when the intrinsic length scale is large enough so that the dynamics is geostrophic to leading order but not so large that the β-effect enters into the dynamics at leading order (but remains, nevertheless, dynamically non-negligible). In contrast to our previous analysis of strong-β LAG models in Part 1, we show that the weak-β models allow for vigorous linear baroclinic instability. For two-layer weak-β LAG models in which the mean depths of both layers are approximately equal, the linear instability problem can exhibit an ultraviolet catastrophe. We argue that it is not possible to establish conditions for the nonlinear stability in the sense of Liapunov for a steady flow. We also show that the finite-amplitude evolution of a marginally unstable flow possesses explosively unstable modes, i.e. modes for which the amplitude becomes unbounded in finite time. Numerical simulations suggest that the development of large-amplitude meanders, squirts and eddies is correlated with the presence of these explosively unstable modes. For two-layer weak-β LAG models in which one of the two layers is substantially thinner than the other, the linear stability problem does not exhibit an ultraviolet catastrophe and it is possible to establish conditions for the nonlinear stability in the sense of Liapunov for steady flows. A finite-amplitude analysis for a marginally unstable flow suggests that nonlinearities act to stabilize eastward and enhance the instability of westward flows. Numerical simulations are presented to illustrate these processes.
Journal of Marine Science and Engineering, Aug 14, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Using Drifters Equipped with Acoustic Tags to Verify the Efficacy of an Array of Acoustic Receivers for Estimating Probability of Fish-Turbine Encounter
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 seconds were usually detected by the receiver array even in fast currents during spring tides but pulse position modulation tags were inadequate. Sometimes very few high residency tag signals were detected when fast tidal currents swept a drifter through the receiver array, so increasing the transmission interval degrades performance at the tidal energy development area. High residency tags suspended close to the sea surface were slightly less likely to be detected if they passed by during calm conditions. Previously measured detection efficiencies were found to slightly overestimate the chances of a high residency tag carried by a drifter being detected as it passed by a receiver. This works elucidates the effectiveness with which acoustically tagged fish are detected in fast, highly turbulent tidal currents and informs the application of detection efficiency measurements to calculate the probability that fish encounter a marine hydrokinetic turbine.
A unified asymptotic derivation of two-layer, frontal geostrophic models including planetary sphericity and variable topography
Physics of Fluids, Sep 1, 1999
Journal of Marine Science and Engineering
An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Mina... more An area has been designated for demonstrating the utility of marine hydrokinetic turbines in Minas Passage, Bay of Fundy. Marine renewable energy may be useful for the transition from carbon-based energy sources, but there is concern for the safety of fish that might encounter turbines. Acoustic receivers that detect signals from acoustically tagged fish that pass through the tidal demonstration area and the detection efficiency of tag signals might be used to estimate the likelihood of fish encountering marine hydrokinetic turbines. The method requires that tagged fish passing through the development area will be reliably detected by a receiver array. The present research tests the reliability with which passing tags are detected by suspending tags beneath GPS-tracked drifters. Drifters carrying high residency Innovasea tags that transmitted every 2 s were usually detected by the receiver array even in fast currents during spring tides but pulse-position modulation tags were inadeq...
Determining Marine Renewable Energy Areas in the Bay of Fundy
American Geophysical Union eBooks, Feb 1, 2016
Abstract: Assessment of tidal current energy in the Bay of Fundy
Tidal stream energy is a renewable energy resource that might be developed to offset carbon emiss... more Tidal stream energy is a renewable energy resource that might be developed to offset carbon emissions. A tidal energy demonstration (TED) area has been designated in Minas Passage, Bay of Fundy, for testing and installing marine hydrokinetic (MHK) turbines. Regulations require quantification of the potential for MHK turbine installations to harm local populations of marine animals. Here we use acoustic telemetry to quantify probability that post smolt Inner Bay of Fundy salmon encounter a turbine installation at the TED area. Previous work has quantified detection efficiency of Innovasea HR acoustic tags as a function of current speed and range from a moored HR2 receiver and also demonstrated that drifters carrying HR tags will be effectively detected when the drifter track crosses the array of HR2 receivers in Minas Passage. Salmon smolts were tagged and released in Gaspereau and Stewiacke Rivers, Nova Scotia, in order that the HR2 receiver array could monitor seaward migration of ...
For many expensive deterministic computer simulators, the outputs do not have replication error a... more For many expensive deterministic computer simulators, the outputs do not have replication error and the desired metamodel (or statistical emulator) is an interpolator of the observed data. Realizations of Gaussian spatial processes (GP) are commonly used to model such simulator outputs. Fitting a GP model to n data points requires the computation of the inverse and determinant of n × n correlation matrices, R, that are sometimes computationally unstable due to near-singularity of R. This happens if any pair of design points are very close together in the input space. The popular approach to overcome near-singularity is to introduce a small nugget (or jitter) parameter in the model that is estimated along with other model parameters. The inclusion of a nugget in the model often causes unnecessary over-smoothing of the data. In this paper, we propose a lower bound on the nugget that minimizes the over-smoothing and an iterative regularization approach to construct a predictor that further improves the interpolation accuracy. We also show that the proposed predictor converges to the GP interpolator.
The attempt to determine the population growth rate from field data reveals several ambiguities i... more The attempt to determine the population growth rate from field data reveals several ambiguities in its definition(s), which seem to throw into question the very concept itself. However, an alternative point of view is proposed that not only preserves the identity of the concept, but also helps discriminate between competing models for capturing the data.
Validating a New Marine Forecasting Tool for Tidal Energy in Grand Passage, Bay of Fundy
Turbulent flow mapping in a high-flow tidal channel using mobile acoustic Doppler current profilers
Renewable Energy, 2021
Abstract In this investigation, instrumented mobile platforms are used to spatially map the turbu... more Abstract In this investigation, instrumented mobile platforms are used to spatially map the turbulent flows in Grand Passage, one of the Bay of Fundy's more energetic tidal channels in Nova Scotia, Canada. The aim is to characterize the flow around the PLAT-I floating tidal energy platform developed by Sustainable Marine Energy Canada (SMEC). GPS-tracked surface drifters equipped with fast-sampling acoustic Doppler current profilers (ADCPs) provide turbulence-resolving vertical profiles of velocity and turbulent kinetic energy dissipation rate along drifter trajectories, while vessel-mounted ADCP transects complement the mean flow velocity measurements. These data are used to construct tridimensional quasi-synoptic maps of mean velocities and turbulence parameters for several stages of the tide around PLAT-I's location including peak ebb and flood currents. The data set includes measurements under natural flow conditions, and while the turbines installed on PLAT-I were both not operational and operational. The measurement techniques and resulting maps successfully capture the spatial and temporal structure of the flow for unsteady conditions for various tidal conditions. The combined wake of the four 6.3 m operational PLAT-I turbines was measured for a single tidal stage. Closer to the turbines, the vertical extent of the wake is about 6 m (approximately one turbine diameter), increasing with distance downstream, while the maximum observed velocity deficit is 26% relative to not operating conditions, decreasing with distance downstream.
Journal of Fish Biology, 2018
Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45 ∘ ... more Atlantic sturgeon Acipenser oxyrinchus surfacing behaviour was investigated in Minas Basin (45 ∘ 20 ′ N; 64 ∘ 00 ′ W) and the Bay of Fundy with pop-up satellite archival tags (MiniPAT) measuring physical variables (pressure, temperature, light). Of six tags deployed during June and July, five provided pop-up locations and two were recovered after c. 4 months. Analysis of recovered archival data revealed that the frequency of surfacing events was highest (78•9%) when A. oxyrinchus were in Minas Basin at depths <10 m. Surfacing frequency decreased substantially when fish migrated into greater depths of the Bay of Fundy (>40 m). The tidal cycle in Minas Basin had a significant relationship to surfacing frequency, with the most surfacing events (49•5%) occurring on the flood tide, from mid-to high-tide. Surfacing events ranged from 0-12 a day and the maximum number occurred between 2300 and 0300 hours. Maximum surfacing ascent speeds ranged from 0•50 to 4•17 m s −1 and maximum descent speeds ranged from 0•17 to 3•17 m s −1. Buoyancy control, by gulping air to inflate the gas bladder, is proposed as the main reason for surfacing behaviour in A. oxyrinchus.
Ocean Engineering, 2017
This paper specifically focuses on site-specific CFD modelling in the context of tidal energy dev... more This paper specifically focuses on site-specific CFD modelling in the context of tidal energy development, and presents results for two sites from the Fundy Tidal Region (FTR) situated in Eastern Canada. The FTR is one of the best and most energetic areas in the world for tidal energy development. To efficiently meet the computational demands of modelling unsteady three-dimensional turbulent flow in complex tidal zone terrains, highly parallel GPU hardware are utilized. Strategically deployed Acoustic Doppler Current Profiler (ADCP) measurements at two tidal turbine locations provide validation of the predictions under ebb and flood flows. The processing methodology of ADCP devices is incorporated into the CFD simulation to improve predicted turbulence levels for validation. The simulations use detached eddy simulation (DES) turbulence modelling with engineered inlet boundary conditions and realistic bathymetry. The inlet boundaries use mean horizontal velocity values interpolated from regional tidal simulations and are perturbed by synthetic turbulence to accelerate boundary layer development. Simulations cover tidal developments from~1.5 to 3 square kilometres with spatial and temporal resolutions of 1-2 m and 0.1 s, respectively.
Journal of Physical Oceanography, 1995
This report presents an update on the extractable power potential of tidal currents in a number o... more This report presents an update on the extractable power potential of tidal currents in a number of passages around Nova Scotia. Since initial reports by EPRI [1] and the Triton [2] were produced, we have gained a better understanding of how the extraction of power from tidal currents affect the tidal system. This report uses numerical simulations and theoretical calculations to predict not only the power that can be extracted but also the resulting reduction in flow through the passage. As such, it gives power estimates along with a first measure of the environmental impact of extracting tidal energy from the system. In particular, the new power estimates are considerably higher for two passages, Minas Channel and Digby Gut, while the estimates for other passages are similar to previous results. Overall, we estimate potential power extraction of 2000 MW in the Minas Channel, 50 to 100 MW in the Digby Neck region and 1 to 2 MW in Cape Breton. In Minas Channel, the mean extractable power is estimated to be 7200 MW, of which 3500 MW can be extracted with a 10% reduction in flow through the channel and 2000 MW can be extracted with a 5% reduction in flow. It should be stressed that Minas Channel, which includes Minas Passage, forms one tidal system with Minas Basin, that is, it is one source of energy and one system that will be changed if energy is extracted. The extractable power from Minas Channel is a reflection of the potential energy in the world's highest tides of the Minas Basin. A reduction in flow through Minas Channel will result in a corresponding reduction in the tides in Minas Basin. This will have important impacts on the intertidal regions that surround the basin. As such, we suggest the 2000 MW power estimate, which limits the reduction in flow to 5%, is the best estimate for the power potential of the Minas Channel region. Finally, it should be noted that the highest water speeds, and thus, highest power densities are found in Minas Passage. As such, it is Minas Passage that has the greatest potential for the development of commercial-scale, tidal turbine arrays. The passages of the Digby Neck region offer the potential of significant tidal power. In particular, the Digby Gut/Annapolis Basin system has a much larger potential than previously estimated. The mean extractable power is 180 MW, of which 67 MW can be extracted with only a 5% reduction in the flow through Digby Gut. However, this estimate comes with the caveat that the flow speed and power densities in Digby Gut are low. Realizing a significant portion of the potential power will require technology that can extract power from flows with speeds of 1 to 2 m/s. On the other hand, Petit and Grand Passages have higher velocities and power densities-similar to those found in Minas Passage. However, these passages lie between two large, open bodies of water. The flow through these small passages is not important in determining the tides in these waters. As such, they only have moderate potential power extraction-33 MW for Petit Passage and 16 MW for Grand Passage. But, it is expected that a reduction in flow through these passages will have a small impact on the surrounding tides. Therefore, Richard H. Karsten 2 power extraction that reduces the flow by 10% (or possibly higher) could be acceptable giving power estimates of 19 MW for Petit Passage and 8.9 MW for Grand Passage. The passages of the Bra D'Or Lakes have a small potential for power extraction-4.6 MW for Great Bra D'Or Channel and 2.2 MW for Barra Strait. The water exchange between the Bra D'Or Lakes and the ocean is a complicated process that supports the ecology of the region. Any power extraction of power should minimize the changes to these exchanges, and therefore we suggest the change in flow through the passages be limited to a 5% reduction, giving power estimates of 1.1 MW for Great Bra D'Or Channel and 0.6 MW for Barra Strait. At this point, we have examined no other sites in Nova Scotia that have the strong tidal currents in a region suitable for large scale tidal power extraction. Ongoing research along the South West Nova Scotia coastline has identified locations suitable for community scale tidal development. These will be reported on in a later report. Finally, estimating the portion of extracted energy that can be converted into useable electricity supplied to the grid is a difficult process. Tidal energy technology is still under development and changes in turbine technology and the design of turbine arrays will affect how much power can be generated. For this report, we only use a very basic model to estimate that 40% of the extractable power can be converted into electricity. We also estimate that the installed capacity necessary to generate this power to be 70% the extractable power. Therefore, the estimated mean extractable power are moderate overestimates of the potential installed capacity of turbine arrays for each passage.