Breakwaters influence coastal wave climate and circulation by blocking and dissipating wave energ... more Breakwaters influence coastal wave climate and circulation by blocking and dissipating wave energy. Accurate representation of these effects is essential to the determination of coastal circulation and wave processes. MIKE21SW and SWAN are two third-generation spectral wave models which are used widely in coastal research and engineering applications. Recent improved versions of the models are able to consider the influence of breakwater structures. In this study, we used available observations to evaluate the accuracy of model simulations of waves in New Haven Harbor, Connecticut, USA, an estuary with three detached breakwaters near the mouth. We then compare the accuracy and computational efficiency of MIKE21SW and SWAN. Both models were executed on the same unstructured triangular grid. The boundary conditions were derived from a bottom mounted ADCP on the offshore side of the breakwaters. Wind forcing was applied using data from the Central Long Island Sound buoy. We find that b...
Proceedings of the IEEE Fifth Working Conference on Current Measurement, 1995
A broadband ADCP and CTD, mounted aboard a towed platform (TOAD), were used to characterize the f... more A broadband ADCP and CTD, mounted aboard a towed platform (TOAD), were used to characterize the front of the Connecticut River plume in Long Island Sound on April 5, 1994. The CTD was at ~0.75 m and the ADCP estimated velocities in 0.25 m intervals from 1.1 m to the bottom, ~10 m. Data were processed in 5-s intervals yielding
Nonlinear mechanisms give rise to overtide frequencies that are integer multiples of the principl... more Nonlinear mechanisms give rise to overtide frequencies that are integer multiples of the principle tidal frequency. The M6 is an overtide with a frequency three times that of the primary M2 semidiurnal tide. Overtides are of interest because they modulate or distort the shape and timing of the fundamental tide. Because their generation and propagation is sensitive to a combination of physical factors, they can also serve as a means by which to evaluate hydrodynamic model performance. Observations in Long Island Sound (LIS) indicate the M6 overtide shows a notable increase in amplitude in the Western Sound compared to the East. M6 generation, however, should be greatest in the East, where the primary M2 current is strongest. We examine the generation and propagation of the M6 in simple channels using numeric and analytic methods and show that, despite its higher frequency, attenuation at the M6 frequency is less than that at the M2. The observed spatial distribution of M6 amplitudes ...
The Seventh ACM International Conference on Underwater Networks and Systems, 2012
ABSTRACT This paper presents collective efforts from four institutions, University of Connecticut... more ABSTRACT This paper presents collective efforts from four institutions, University of Connecticut, University of Washington, University of California, Los Angeles, and Texas A&M University, on a community Ocean Testbed for Underwater Networks Experiments (Ocean-TUNE). This proposed community testbed will enable a wide range of research in the areas of underwater communications, networking, engineering, and marine science, and hence will promote unprecedented progress towards practical solutions in diverse aquatic applications.
With an analytic model, this paper describes the subtidal circulation in tidally dominated channe... more With an analytic model, this paper describes the subtidal circulation in tidally dominated channels of different lengths, with arbitrary lateral depth variations. The focus is on an important parameter associated with the reversal of the exchange flows. This parameter (δ) is defined as the ratio between the channel length and one-quarter of the tidal wavelength, which is determined by water depth and tidal frequency. In this study, a standard bottom drag coefficient, CD = 0.0025, is used. For a channel with δ smaller than 0.6–0.7 (short channels), the exchange flow at the open end has an inward transport in deep water and an outward transport in shallow water. This situation is just the opposite of channels with a δ value larger than 0.6–0.7 (long channels). For a channel with a δ value of about 0.35–0.5, the exchange flow at the open end reaches the maximum of a short channel. For a channel with a δ value of about 0.85–1.0, the exchange flow at the open end reaches the maximum of a...
... 1. Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA ... more ... 1. Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA 2. Corresponding author. email: diane.bennett@uconn.edu 1 Page 2. 2 Journal of Marine Research [68, 1 Figure 1. Bathymetric map of Long Island Sound. ...
We present a simple advection-dispersion model for the subtidal salt distribution in estuaries wi... more We present a simple advection-dispersion model for the subtidal salt distribution in estuaries with linearly varying cross-sectional area and a nonzero net salt flux. A novel analytic solution allows investigation of the dependence of the curvature and gradient of the longitudinal salinity distribution on runoff, dispersion coefficient, and channel contraction or expansion. The model predicts that in estuarine segments that contract toward the fresher boundary, the salinity gradient is stronger than in a prismatic channel. When the dispersion coefficient is large compared to the salinity intrusion lengthscale, $\frac{LR}{A0 (the product of segment length and net volume flux divided by cross-sectional area at the ocean boundary), the curvature of the salt concentration may be negative, a characteristic not possible in uniform channel models. The main effect of up-estuary salt flux is to strengthen the salinity gradient. The model can be extended to multiple segments in order to simulate geometrically complicated estuaries. The model is employed to estimate an effective dispersion coefficient and to describe the salinity variation in the western 53 km of Long Island Sound where the cross section of the basin varies linearly. Using 8 years of monthly observations at seven stations we find that, since the curvature of the vertically averaged salinity is negative, the model and data are consistent only if the net volume flux and salt flux are toward the fresher boundary, the East River. Combining prior estimates of the magnitudes of the fluxes and their uncertainties with the model and salinity observations using a least squares approach, we estimate the dispersion coefficient for the Western Sound as 580 m2/s.
Breakwaters influence coastal wave climate and circulation by blocking and dissipating wave energ... more Breakwaters influence coastal wave climate and circulation by blocking and dissipating wave energy. Accurate representation of these effects is essential to the determination of coastal circulation and wave processes. MIKE21SW and SWAN are two third-generation spectral wave models which are used widely in coastal research and engineering applications. Recent improved versions of the models are able to consider the influence of breakwater structures. In this study, we used available observations to evaluate the accuracy of model simulations of waves in New Haven Harbor, Connecticut, USA, an estuary with three detached breakwaters near the mouth. We then compare the accuracy and computational efficiency of MIKE21SW and SWAN. Both models were executed on the same unstructured triangular grid. The boundary conditions were derived from a bottom mounted ADCP on the offshore side of the breakwaters. Wind forcing was applied using data from the Central Long Island Sound buoy. We find that b...
Proceedings of the IEEE Fifth Working Conference on Current Measurement, 1995
A broadband ADCP and CTD, mounted aboard a towed platform (TOAD), were used to characterize the f... more A broadband ADCP and CTD, mounted aboard a towed platform (TOAD), were used to characterize the front of the Connecticut River plume in Long Island Sound on April 5, 1994. The CTD was at ~0.75 m and the ADCP estimated velocities in 0.25 m intervals from 1.1 m to the bottom, ~10 m. Data were processed in 5-s intervals yielding
Nonlinear mechanisms give rise to overtide frequencies that are integer multiples of the principl... more Nonlinear mechanisms give rise to overtide frequencies that are integer multiples of the principle tidal frequency. The M6 is an overtide with a frequency three times that of the primary M2 semidiurnal tide. Overtides are of interest because they modulate or distort the shape and timing of the fundamental tide. Because their generation and propagation is sensitive to a combination of physical factors, they can also serve as a means by which to evaluate hydrodynamic model performance. Observations in Long Island Sound (LIS) indicate the M6 overtide shows a notable increase in amplitude in the Western Sound compared to the East. M6 generation, however, should be greatest in the East, where the primary M2 current is strongest. We examine the generation and propagation of the M6 in simple channels using numeric and analytic methods and show that, despite its higher frequency, attenuation at the M6 frequency is less than that at the M2. The observed spatial distribution of M6 amplitudes ...
The Seventh ACM International Conference on Underwater Networks and Systems, 2012
ABSTRACT This paper presents collective efforts from four institutions, University of Connecticut... more ABSTRACT This paper presents collective efforts from four institutions, University of Connecticut, University of Washington, University of California, Los Angeles, and Texas A&M University, on a community Ocean Testbed for Underwater Networks Experiments (Ocean-TUNE). This proposed community testbed will enable a wide range of research in the areas of underwater communications, networking, engineering, and marine science, and hence will promote unprecedented progress towards practical solutions in diverse aquatic applications.
With an analytic model, this paper describes the subtidal circulation in tidally dominated channe... more With an analytic model, this paper describes the subtidal circulation in tidally dominated channels of different lengths, with arbitrary lateral depth variations. The focus is on an important parameter associated with the reversal of the exchange flows. This parameter (δ) is defined as the ratio between the channel length and one-quarter of the tidal wavelength, which is determined by water depth and tidal frequency. In this study, a standard bottom drag coefficient, CD = 0.0025, is used. For a channel with δ smaller than 0.6–0.7 (short channels), the exchange flow at the open end has an inward transport in deep water and an outward transport in shallow water. This situation is just the opposite of channels with a δ value larger than 0.6–0.7 (long channels). For a channel with a δ value of about 0.35–0.5, the exchange flow at the open end reaches the maximum of a short channel. For a channel with a δ value of about 0.85–1.0, the exchange flow at the open end reaches the maximum of a...
... 1. Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA ... more ... 1. Department of Marine Sciences, University of Connecticut, Groton, Connecticut, 06340, USA 2. Corresponding author. email: diane.bennett@uconn.edu 1 Page 2. 2 Journal of Marine Research [68, 1 Figure 1. Bathymetric map of Long Island Sound. ...
We present a simple advection-dispersion model for the subtidal salt distribution in estuaries wi... more We present a simple advection-dispersion model for the subtidal salt distribution in estuaries with linearly varying cross-sectional area and a nonzero net salt flux. A novel analytic solution allows investigation of the dependence of the curvature and gradient of the longitudinal salinity distribution on runoff, dispersion coefficient, and channel contraction or expansion. The model predicts that in estuarine segments that contract toward the fresher boundary, the salinity gradient is stronger than in a prismatic channel. When the dispersion coefficient is large compared to the salinity intrusion lengthscale, $\frac{LR}{A0 (the product of segment length and net volume flux divided by cross-sectional area at the ocean boundary), the curvature of the salt concentration may be negative, a characteristic not possible in uniform channel models. The main effect of up-estuary salt flux is to strengthen the salinity gradient. The model can be extended to multiple segments in order to simulate geometrically complicated estuaries. The model is employed to estimate an effective dispersion coefficient and to describe the salinity variation in the western 53 km of Long Island Sound where the cross section of the basin varies linearly. Using 8 years of monthly observations at seven stations we find that, since the curvature of the vertically averaged salinity is negative, the model and data are consistent only if the net volume flux and salt flux are toward the fresher boundary, the East River. Combining prior estimates of the magnitudes of the fluxes and their uncertainties with the model and salinity observations using a least squares approach, we estimate the dispersion coefficient for the Western Sound as 580 m2/s.
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Papers by James O'Donnell