Tidal Channel

Los canales de marea en el departamento de Tumbes, Perú, albergan diversas especies de peneidos, como Penaeus stylirostris y P. vannamei, esta última de gran importancia económica para el país. En 2017 se evaluaron 560 ejemplares de langostinos silvestres en dos periodos de muestreo (mayo-junio y septiembre-noviembre), provenientes de siete canales de marea para determinar la prevalencia de las enfermedades de notificación obligatoria: Síndrome de la Mancha Blanca (VSMB), Infección Hipodérmica y Hematopoyética Infecciosa (VNHHI), Necrosis Hepatopancreática (HPN), Síndrome del Taura (ST), Mionecrosis Infecciosa (VMNI) y Síndrome de la Cabeza Amarilla (VCA1) mediante la técnica del PCR. Se detectó la presencia de tres de los siete patógenos. La mayor prevalencia del estudio fue de VNHHI (6.35%) distribuida en los siete canales de marea, seguido por HPN (2.65%) en cinco canales de marea y VSMB (0.55%) presente en tres canales, pero únicamente en el primer periodo de muestreo.

Denne oppgaven ville ikke blitt slik den er nå uten veilederne mine, Ole Anders Nøst og Knut Barthel. Tusen takk for all tiden dere satt av forå diskutere de ulike fenomenene, og ikke minst forå hjelpe meg med skriveprosessen. Jeg er svaert takknemlig for at dere lot meg få dure på med det jeg til enhver tid fant interessant, selv om det tok litt tid før jeg presenterte utkast til teoridelen og den slags. Uten den friheten tilå gjøre det jeg følte for ville det sikkert ikke vaert like artigå skrive oppgaven-takk for tilliten, rett og slett. Videre vil jeg takke Knut for at jeg ble interessert i numerisk modellering (et fag jeg tilå begynne med var skeptisk til, pc-greier var skumle greier!). Uten den gnisten jeg fikk i GEOF211 tror jeg det ville blitt veldig tungtå skrive denne oppgaven. Takk til alle dere i Fagutvalget som deltok på FIFA kvelder, fuktige badstuhelger i utkanten av Voss, samt for vaffelsøndagene når eksamensperioden sto på som verst. Jeg savner de jeg har feira 17. mai med de sisteårene, de som ble med på håpløse turer i snøstorm over Vidden (gjerne dagen før eksamen) og ikke minst for hverdagen-jeg savner kaffepausene (og frokostpausene, lunsjpausene, middagspausene-egentlig for pausene)! Det var artigå bli (litt mer) voksen i Bergen! De sniker seg kanskje ikke forbi forsiden, men det få så vaere: Mamma og Pappa, jeg tror ikke jeg kan takke dere nok for alt dere gjør for meg-tusen ganger holder i hvert fall ikke!

The paper is focusing on the tides and on the strong tidal current generated in the western fjords of Svalbard. Numerical model is chosen as a tool to study the barotropic tides. Model results are compared against measured sea level and drifters. Numerical modeling and observation of tides point that the tidal amplitude does not change strongly in these fjords but the tidal currents are enhanced in several locations, namely at the entrance to the Dickson Fjord, in the narrow passages in proximity to Svea, and in the central part of Van Keulenfjorden. As the strongest currents have been found at the passages at Akseløya Island we have focused our research on this location. The narrow northern channel (Akselsundet) at Akseløya is the main waterway to Svea coal mines. Tidal currents computed and observed at the northern tip of Akseløya Island can reach amplitude from 2 to 3 m s À1. Observation of the deployed drifters and calculation of the seeded particles in the passage at Akseløya depicted a complicated pattern of eddies. The jet-like currents and eddies are quite different at the ebb and flood tide phases. As the Akseløya Island orientation relative to the shore is different for the flood and ebb waters the flow through Akselsundet is differently constrained by this geometry. The observations show that the oscillating tidal motion causes large excursions of the water particle. The drifters released in the passage during flood ended up trapped in the eddy on the eastern side of the island.

In this paper we are interested in the approximation of continuous surface texture profiles defined only at discretely obtained points. A continuous representation is required in order to be able to apply filtration methods that assume uniform data spacing to practical data that in general is not uniformly spaced. By reconstructing surface profiles as natural cubic spline interpolants accurately using numerically stable fitting algorithms, we can provide a mathematically sound basis on which to compute surface texture profile parameters. As an important direct benefit, parameters involving the integrals of surface profiles can be calculated directly from the spline interpolant. Examples are given to illustrate the advantages of using this reconstruction method.

The tidal circulation in the semi-enclosed Boulogne harbour (eastern English Channel) is measured during the various stages of the tidal cycle with a low-cost towed Acoustic Doppler Current Profiler (ADCP) system for the first time. The system is equipped with an interpolation algorithm which allows reconstructing space-time evolution of the velocity field for surveys whose duration is comparable or larger than the typical time of tidal variation (1-2 h). The method employs space-time velocity covariances derived from a numerical simulation of the surveyed area by a high-resolution relocatable model BModel for Applications on Regional Scale(MARS). The covariances are utilized by the optimal interpolation algorithm to obtain the most likely evolution of the velocity field under the constraints provided by the ADCP observations and their error statistics. Technically, the MARS model run provides the first guess (background) evolution of the velocity field in the surveyed area which is then corrected by the data in a statistically consistent manner as it explicitly takes into the account both observational and modeling errors. The quality of the velocity reconstruction was validated against independent bottom-mounted ADCP data, the background model evolution, and against the results of spatial interpolation by Kriging technique. All tests demonstrated significant (30 to 60 %) reduction of the model-data misfit for the velocity field obtained as a result of space-time optimal interpolation. Although the method was applied to recover surface circulation, it can be extended for assessment of the full 4D tidal flow dynamics using the data recorded throughout the entire water column.

Most geological and soil maps are not detailed enough to represent the high lateral and vertical textural variability in the subsoil of coastal lowlands. Intensive sampling campaigns need to be carried out to quantify this variability. As an alternative, a proximal soil sensing procedure based on a single survey with an electromagnetic induction instrument was used to map a 6.5 ha Holocene tidal area in Belgium. We investigated the effectiveness of a multi-receiver apparent electrical conductivity (ECa) survey for mapping the trace of tidal paleochannels. From a limited number of augerings, a three-layered soil was observed composed of a clayey top layer, a clayey infilling of the tidal channel above a subsoil consisting of coarse sandy material. A fitting procedure allowed modelling the conductivities of both subsurface layers, after which the four simultaneous ECa measurements were combined to model the depth of the interfaces between the three layers. The predictions were validated by 16 depth observations along a 150 m transect. A correlation coefficient of 0.91, with an average error of 0.23 m, was found between the predicted and measured depths of the clay-sand interface. We concluded that the dense ECa measurements (2 by 2 m resolution) allowed reconstructing a precise three-dimensional representation of the tidal channels.

Most geological and soil maps are not detailed enough to represent the high lateral and vertical textural variability in the subsoil of coastal lowlands. Intensive sampling campaigns need to be carried out to quantify this variability. As an alternative, a proximal soil sensing procedure based on a single survey with an electromagnetic induction instrument was used to map a 6.5 ha Holocene tidal area in Belgium. We investigated the effectiveness of a multi-receiver apparent electrical conductivity (ECa) survey for mapping the trace of tidal paleochannels. From a limited number of augerings, a three-layered soil was observed composed of a clayey top layer, a clayey infilling of the tidal channel above a subsoil consisting of coarse sandy material. A fitting procedure allowed modelling the conductivities of both subsurface layers, after which the four simultaneous ECa measurements were combined to model the depth of the interfaces between the three layers. The predictions were validated by 16 depth observations along a 150 m transect. A correlation coefficient of 0.91, with an average error of 0.23 m, was found between the predicted and measured depths of the clay-sand interface. We concluded that the dense ECa measurements (2 by 2 m resolution) allowed reconstructing a precise three-dimensional representation of the tidal channels.

Most geological and soil maps are not detailed enough to represent the high lateral and vertical textural variability in the subsoil of coastal lowlands. Intensive sampling campaigns need to be carried out to quantify this variability. As an alternative, a proximal soil sensing procedure based on a single survey with an electromagnetic induction instrument was used to map a 6.5 ha Holocene tidal area in Belgium. We investigated the effectiveness of a multi-receiver apparent electrical conductivity (ECa) survey for mapping the trace of tidal paleochannels. From a limited number of augerings, a three-layered soil was observed composed of a clayey top layer, a clayey infilling of the tidal channel above a subsoil consisting of coarse sandy material. A fitting procedure allowed modelling the conductivities of both subsurface layers, after which the four simultaneous ECa measurements were combined to model the depth of the interfaces between the three layers. The predictions were validated by 16 depth observations along a 150 m transect. A correlation coefficient of 0.91, with an average error of 0.23 m, was found between the predicted and measured depths of the clay-sand interface. We concluded that the dense ECa measurements (2 by 2 m resolution) allowed reconstructing a precise three-dimensional representation of the tidal channels.

Tidal circulation and tidal stream resource in Aldemey Race (Raz Blanchard) were assessed by using a towed acoustic Doppler current profiler (ADCP) system and tidal modeling. Optimal Interpolation (OI) was applied to process the underway velocity measurements recorded at neap tide flood and ebb flow. The interpolation technique allows reconstructing space-time evolution of the velocity field within the domain during surveying periods. The method employs velocity covariances derived from numerical simulations by a 2D hydrodynamic model MARS. Model covariances are utilized by the OI algorithm to obtain the most likely evolution of the velocity field under the constraints provided by the ADCP observations and their error statistics. The resulting velocity fields were used for assessing the tidal stream resource at site. The largest overall difference between the kinetic power density derived from simulated and interpolated velocity fields was found for ebb tide. Model simulations constrained by velocity measurements demonstrated a significant (up to 30%) decrease of power available in the flow. A significant change in spatial pattern of power density distribution was also identified. It is demonstrated that by merging high resolution velocity measurements at tidal energy site with modeling the tidal stream potential estimation becomes more accurate.

Resumen El estero Domingo Rubio está situado en la margen izquierda de la desembocadura del río Tinto (37º 12' N, 6º 54' W, Palos de la Frontera, Huelva). Tiene 6 km de longitud, una anchura máxima de 1 km y ocupa una extensión de 480 ha. Este estero es un sistema típico de marisma salobre sometido a una clara influencia mareal, con un régimen semidiario de inundación. Actualmente, debido a la colmatación, la influencia mareal sólo afecta al curso bajo del estero, habiéndose modificado sus cursos medio y alto hacia un ambiente de carácter lacustre. El estero se encuentra sometido a diversos impactos ambientales: las aguas contaminadas con elementos traza del río Tinto y las pluviales y de drenaje de los terrenos en los que se ubican diversas industrias químicas y agrícolas. En el presente estudio se ha puesto de manifiesto que la contaminación con As, Cd, Cu, Cr, Ni, Pb y Zn de los suelos está altamente relacionada con la salinidad: aumenta aguas abajo del estero, siendo muy importante en el tramo mareal. Sin embargo, en las plantas (Halimione, Astrhocnemun, Tamarix y Paspalum), sólo se encuentran algunos valores Cu y Cr ligeramente superiores a los considerados normales. Especies típicamente acumuladoras de elementos traza, como Cistus y Salix, en zonas de baja contaminación, muestran ligeras acumulaciones de Cd, Cu, Cr, Mn y Zn.

Este trabajo, realizado como una primera aproximación en la Investigación Biogeoquímica de Metales en el área de Mocoa-Putumayo (Gaviria, 1981), dentro del Proyecto Landsat-Mocoa, resume los resultados de análisis para material foliar de algunas especies vegetales recolectadas a finales de 1980 en el área del Prospecto de Pórfido Cuprífero de Mocoa y sus alrededores, que explora INGEOMINAS-NACIONES UNIDAS. Se hacen las interpretaciones de los resultados preliminares y se dan algunas recomendaciones para la continuación del programa propuesto. Las primeras muestras indican que efectivamente la presencia de minerales de Cu y Mo (Zn), afectan el contenido de dichos elementos en la vegetación que crece dentro del área de influencia de los depósitos, y será posible determinar las especies indicadoras que servirán de ayuda a la prospección de yacimientos minerales en regiones selváticas.

The bedforms and equivalent roughness sizes in tidal channels of the Central Dithmarschen Bight on the basis of field measurements and numerical modeling are studied. Side scan sonar and echo sounder were employed to acquire bedform dimensions, while acoustic profilers were used to measure current velocities. The equivalent roughness size is estimated on the basis of best fit line of velocities in the bottom boundary layer. The obtained bedform dimensions and flow conditions are used to check existing equations for estimation of bedform dimensions and equivalent roughness sizes. Numerical model simulations are also carried out in conjunction with modified equations to develop maps of bedforms and equivalent roughness sizes in the study area. In general, the empirical equations are able to predict bedform dimensions and equivalent roughness sizes in shallow areas.

An analysis of transient momentum balances is carried out to elucidate circulation, dynamics, and exchange mechanisms at shallow barotropic tidal inlets. Circulation is computed using a depth-integrated, fully nonlinear, time-stepping, finite-element model with variably spaced grids having horizontal resolution down to 50 m. Velocity and elevation fields from the model are used to directly evaluate the contribution of each term in the momentum equations to the overall momentum balance. A transformation of the x-y momentum terms into an s-n coordinate system is used to simplify the interpretation of the dynamics and provide vivid illustrations of the forces and resulting accelerations in the flow. The analysis is conducted for an idealized inlet and contrasted with a highly detailed model of Beaufort Inlet, North Carolina. Results show that momentum balances in the immediate vicinity of these inlets vary significantly in time and space and oscillate between two dynamical states. Near maximum ebb or flood, the alongstream momentum balances are dominated by advective acceleration, pressure gradient, and bottom friction. Cross-stream balances are dominated by centrifugal acceleration and pressure gradients. Near slack, balances more closely follow linear wave dynamics, with local accelerations balancing pressure gradients, and (to a lesser degree) Coriolis. Comparisons between the idealized inlet and Beaufort Inlet show broad similarities in these momentum balances. However, natural inlet geometry and bottom topography, as well as the tidal transmission characteristics of the sounds behind Beaufort Inlet produce strong asymmetries. Moreover, momentum balances are highly localized, often with subkilometer length scales. The dynamics are used to explain the physical mechanisms for inlet exchange. In particular, the results indicate that the cross-stream dynamics generate a ''wall'' along the length of an inlet during the stronger phases of the tide. The wall is established by opposing cross-inlet pressure gradients and centrifugal forces, and it poses a significant barrier to cross-inlet exchange during the stronger phases of the tide but is absent near slack.

Resumen El estero Domingo Rubio está situado en la margen izquierda de la desembocadura del río Tinto (37º 12' N, 6º 54' W, Palos de la Frontera, Huelva). Tiene 6 km de longitud, una anchura máxima de 1 km y ocupa una extensión de 480 ha. Este estero es un sistema típico de marisma salobre sometido a una clara influencia mareal, con un régimen semidiario de inundación. Actualmente, debido a la colmatación, la influencia mareal sólo afecta al curso bajo del estero, habiéndose modificado sus cursos medio y alto hacia un ambiente de carácter lacustre. El estero se encuentra sometido a diversos impactos ambientales: las aguas contaminadas con elementos traza del río Tinto y las pluviales y de drenaje de los terrenos en los que se ubican diversas industrias químicas y agrícolas. En el presente estudio se ha puesto de manifiesto que la contaminación con As, Cd, Cu, Cr, Ni, Pb y Zn de los suelos está altamente relacionada con la salinidad: aumenta aguas abajo del estero, siendo muy importante en el tramo mareal. Sin embargo, en las plantas (Halimione, Astrhocnemun, Tamarix y Paspalum), sólo se encuentran algunos valores Cu y Cr ligeramente superiores a los considerados normales. Especies típicamente acumuladoras de elementos traza, como Cistus y Salix, en zonas de baja contaminación, muestran ligeras acumulaciones de Cd, Cu, Cr, Mn y Zn.

This paper presents a comparison of two conventional detiding techniques carried out for ship-mounted acoustic Doppler current profiler (ADCP) data collected in the European shelf area of the Celtic Sea during the summer of 1998. One technique consisted of extracting the vertically averaged tidal currents obtained from a barotropic three-dimensional numerical tidal model. The second technique consisted of fitting the spatiotemporal ADCP data using least squares and polynomial spatial functions. In the least squares technique, the incorporation of zero velocity normal to the coast appears to improve the estimation of the tidal currents near the coast. Quantitative comparisons of the results from both techniques with historical current meter observations are shown. However, both methods showed limitations in accurately representing the tidal currents in the study area. Consequently, an alternative detiding technique is proposed. This technique consists of blending the tidal currents d...

Intratidal variability and flux of salt, chlorophyll-a and suspended materials were evaluated in a shallow tropical tidal channel linking a coastal lagoon to the western Gulf of Mexico. Velocity, temperature and conductivity were used to calculate the fluxes. Data were recorded during three tidal velocity cycles (tvc) under extreme river discharge conditions. Chlorophyll-a and suspended materials were determined below the surface. In both seasons (dry and rainy), the flow was ebb-dominated and with longer duration than when in flood. Maximum current velocities were 0.30 m s-1 in May (dry season) and 0.60 m s-1 in September (rainy season). In the dry season the mean chlorophyll-a export was of 7.56 Kg over tvc while the import was of 3.32 Kg. In the rainy season mean export (47.3 Kg) was 6 times greater than the import (7.93 Kg over tvc). Phytoplankton was dominated by organisms of marine origin. The mean of exported, suspended materials in the rainy season (111.3 Kg) was 4.6 times g...

The eddy patterns in the harbour of Zeebrugge are studied using TELEMAC-3D and compared to available measurement data. It was found that during flood a clockwise eddy exists, generated by a strong jet near the eastern side of the harbour entrance. This eddy generates a second counter­ clockwise eddy, which persists in the harbour during the ebb phase, whereas the primary eddy disappears. A sensitivity study was performed to investigate the influence of the turbulence model, the bed roughness and the advection scheme. It appeared that the modelled eddy patterns are quite sensitive to the settings that are used for all these three parameters. I. In t r o d u c t io n The harbour of Zeebrugge is one of the most important Belgian seaports. The area surrounding Zeebrugge is characterised by strong tidal flows, with a tidal amplitude up to 5m during spring tide. In the harbour, complex eddy flow patterns are found, varying throughout the tidal cycle. Understanding these patterns is import...

Thirteen repetitions of a cross-channel transect in the Khuran Channel within the Strait of Hormuz allowed the description of the mean flow and semidiurnal tidal properties of a northsouth transect. Water velocity profiles were obtained with a 614.4 kHz TRDI Work Horse Broadband ADCP along this 3.3 km long transect on 10 October 2014, the third day of secondary spring tide. The M2, M4 and M6 frequencies were separated from the observed current using sinusoidal least squares regression analysis. The semidiurnal tidal currents along this transect exhibited typical amplitudes of 160-170cm/s, decreasing toward coastal waters. The mean flow which confirmed the occurrence of asymmetry between ebb and flood phase of tidal current in Khuran Channel were ebb dominant in the deeper part of the channel and southern slopes and flood dominant over the shallower areas, with greatest magnitudes (10 cm/s) near the surface mainly in the deeper parts of the northern side of the channel. The tidal cur...

Persistent residual eddies in a tidal channel in Wassaw Sound, Georgia, were resolved through shipboard observations. The residual eddies appear to be linked to bathymetry and coastlines. The semidiurnal tidal constituent, which explains about 90% of the variability of the data, was found to be a standing wave and the tidal wave propagation induced residual flow was minimal, so the advective nonlinearity was one of the major contributors to the residual eddies. From the vorticity point of view, if the lateral friction is neglected, three terms contribute to the generation of the relative vorticity in the depth-averaged vorticity equation. An important fact is that all these terms include the depth function: the interaction between the advection and bathymetry gradient, the interaction between advection and bathymetry, and the interaction between mean pressure gradient and the bathymetry gradient.

We present the results of a study focused on the tidal regime of a shallow channel with a large intertidal area. Data from a vessel-towed acoustic Doppler current profiler (ADCP) were used to infer tidal constituents for both tidal elevation and tidal current along an upstream portion of the Okatee River, South Carolina. The tidal elevation is estimated from the depth recorded by the moving ADCP. This tidal elevation is then used to correct the vertical coordinates of each depth bin below the ADCP for the velocity profiles. The ability to resolve both tidal elevation and velocity allows us to determine that the tide is a standing wave. A statistical analysis demonstrates that the along-channel velocity has a stronger tidal signal (larger R 2 values) than the across-channel velocity. When only the M 2 and mean components are included in the harmonic analysis, about 75% of the covered area along the ship track has a ''good fit,'' where at least 70% of the variability can be explained by the tidal and mean components. By adding the M 4 component to the harmonic analysis, an additional 2% of the covered area has ''good fit'' for the elevation, depth-averaged velocity, and mid-depth velocity, but 12% for the near-surface velocity. The observed spatial distribution of the residual flow is in reasonable agreement with that predicted by an unstructured grid, finite-volume coastal ocean model (FVCOM).

Observations of currents, water levels, winds, and bathymetry collected for a month at an unstratified, narrow (150 m), shallow (8 m), 908 tidal inlet bend are used to evaluate an analytical model for curvature-driven flow and the effects of local wind on the cross-channel circulation. Along-channel flows ranged from 21.0 to 1.4 m/s (positive is inland), and the magnitudes of cross-channel flows were roughly 0.1-0.2 m/s near the outer bank of the bend. Cross-channel observations suggest the lateral sea-surface gradients and along-channel flows are tidally asymmetric and spatially variable. The depth-averaged along-channel dynamics are consistent with a balance between the surface tilt and centrifugal acceleration. The vertical structure and magnitude of cross-channel flows during weak winds are consistent with a one-dimensional depth-varying balance between centrifugal acceleration, bottom stress, and diffusion. Low-passed (to remove tides) surface and bottom cross-channel flows are correlated (r 2 5 0.5-0.7) with cross-channel wind velocity, suggesting that winds can enhance or degrade the local-curvature-induced, two-layer flow and can drive three-layer flow. The observed flow response to the wind is larger than that expected from a one-dimensional balance, suggesting that two-dimensional and three-dimensional processes may be important.

Tidal currents of up to 50cms-1 occur in the Hauraki Gulf, NZ, the location for the 2000 and 2003 America’s Cup racing. The average speed difference between the race winner and loser is usually much less than 0.5%. Thus exploiting even weak environmental gradients in currents can provide a competitive advantage. Rules prevent receiving information, such as real-time currents, while racing which led to the development of an onboard tidal current prediction system to assist with tactical strategies during racing. The prediction system is based on a combination of measurements and numerical modelling. Vessel mounted Acoustic Doppler Current Profiler measurements over three spring tidal cycles were made in high current gradient areas of the Inner Gulf. To cover unmeasured areas results from a Inner Gulf 250m resolution 3D numerical model were used. A composite of measured data where it was available and model results in other areas with a transition region between them was used to const...

At tidal inlets large amounts of water are exchanged with the adjacent sea during the tidal cycle. The residual flows, the net effect of ebb and flood, are generally small compared to the gross flux, they vary in magnitude and sign from one tidal period to the other, and their long-term mean varies from year to year. Here we focus on the temporal variability of the residual flows in the Marsdiep tidal inlet, which is the western-most inlet of the Wadden Sea, a tidal lagoon along the coasts of the Netherlands, Germany and Denmark. We compare the transport from a high-resolution numerical model with the transport from velocity profile data collected beneath a ferry that crosses the inlet daily. The comparison works in two ways: for the areas and times covered by the measurements, the data serves to validate the model, and conversely, the model is employed to assess the consequences of spatial and temporal gaps in the data. Modeled and observed transports over the region of the flow that is covered by the ADCP are in good agreement for gross and residual quantities. Results indicate that uncertainties due to spatial gaps can be overcome with a simple extrapolation approach applied to the velocity profiles, whereas uncertainties due to temporal gaps are more problematic and leave large discrepancies in the residuals. 3 Summary of statistics of the residuals for the year 2009 based on the full series (Full), the series restricted to the times of the ferry crossing (6AM-10PM), the series with gaps as in the observations (ADCP scope), and the residuals obtained by subtracting from the full series the reconstructed series obtained with harmonic analysis. Also shown the Pearson's r between estimates with the full series (first row, assumed here to be the true residual transport) and estimates with all other approaches (the rest of the rows). All quantities in m 3 s −1 , except for the skewness and the coefficient of correlation that have no units. .

A simple but accurate interpolation procedure for obtaining the three-dimensional distribution of three-component velocity data, from moving acoustic Doppler current profiler (ADCP) observation data, is proposed. For understanding actual flow structure within a river with complex bathymetry, the three-dimensional mean velocity field provides a basic picture of the flow. For obtaining the three-dimensional distribution of three-component velocity data, in this work, anisotropic gridding was introduced in order to remove the random component of measured velocity data caused by the turbulence of the flow and measurement error. A continuity correction based on the pressure equation was used to reduce both random and systematic errors. The accuracy of the developed method was evaluated using three-dimensional flow simulation data from a detached-eddy simulation (DES). By using the procedure developed, the complex flow structure surrounding the spur-dikes section in the Uji River was successfully visualized and explored. The proposed method shows superiorities in both accuracy and consistency for the interpolated velocity field, as compared to the Kriging and Inverse-Distance Weighted (IDW) methods.

Current measurements, from shipboard and moored instruments, from the Strait of Sicily are examined to evaluate the importance of tidal and subtidal currents during summer 2000. The results show that the principal tidal components (M2, K1, S2, and O1) are particularly important in the western shelf and sill region but are significantly less important over the eastern shelf and almost negligible in the central part of the strait. There is a significant internal tide in the narrowest passage through the western sill. The residual (nontidal) currents describe the main pathways and local structures of Atlantic Water as it crosses the strait. The residual currents are compared with the geostrophic velocity calculated from simultaneous hydrographic measurements.

The evolution of a barotropic coastal current in the presence of a bottom ramp-shaped topography is studied by means of laboratory experiments and numerical simulations. The experiments are performed in a rectangular rotating tank filled with freshwater. The fluid depth is shallow at one side of the domain and deeper at the other side, and both regions are divided by a narrow slope, whose depth contours are perpendicular to the long sides of the tank. A current approaching the slope is produced along one of the vertical walls, having the boundary at its right. Two configurations are analyzed: when the current flows from shallow to deep water and when flowing in the opposite direction. In the first scenario, the current is divided in two parts, one of them following the coastline. The other part of the current pairs with a cell of negative relative vorticity generated at the slope due to squeezing effects, forming a dipolar structure moving offshore, back toward the shallow side. In ...

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...

Greater Cook Strait (GCS) lies between the North and the South Islands of New Zealand. Its location at the convergence of the Pacific and Indo-Australian tectonic plates leads to interesting bathymetry with an adjacent shallow shelf and deep ocean trench as well as numerous crossing faults and complex shoreline geometry. Our purpose in this study is to examine tides and currents in GCS and, in particular, identify the major forcing mechanisms for the residual currents. Toward this end, we use an unstructured-grid numerical model to reproduce the tides and currents, verify these results with observations and then use the model to separate the various forcing mechanisms.

The evolution of a barotropic coastal current in the presence of a bottom ramp-shaped topography is studied by means of laboratory experiments and numerical simulations. The experiments are performed in a rectangular rotating tank filled with freshwater. The fluid depth is shallow at one side of the domain and deeper at the other side, and both regions are divided by a narrow slope, whose depth contours are perpendicular to the long sides of the tank. A current approaching the slope is produced along one of the vertical walls, having the boundary at its right. Two configurations are analyzed: when the current flows from shallow to deep water and when flowing in the opposite direction. In the first scenario, the current is divided in two parts, one of them following the coastline. The other part of the current pairs with a cell of negative relative vorticity generated at the slope due to squeezing effects, forming a dipolar structure moving offshore, back toward the shallow side. In addition, a weak current moving inshore along the slope is clearly formed. In the second configuration, when the flow goes from deep to shallow water, a part of or even the whole current might be forced to move along the contours of the topography, away from the coast. In this case there is no dipole formation. The experiments are well reproduced by means of quasigeostrophic numerical simulations, which allow a more detailed systematic study of the influence of flow parameters such as the topography height and the width of the slope.

We present two new methods for approximating elevation data from contours to a grid. The first repeatedly interpolates new contour lines between the original ones. The second starts with any interpolated or approximated surface, determines its gradient lines, and does a Catmull-Rom spline interpolation along them to improve the elevations. We compare the new methods to a more classical thin-plate approximation on various data sets. The new methods appear visually smoother, with the undesirable terracing effect much reduced.

Cross-sectional gradients in water levels and velocities play a determining role in the circulation dynamics of tidal rivers and estuaries. Documenting and analyzing their variability throughout a tidal cycle require observations with high spatial and temporal resolution. A survey strategy and a data analysis procedure have been designed to obtain continuous and synoptic water level and velocity fields over a tidal cycle, along 13 cross-sections of the St. Lawrence fluvial estuary dominated by large tidal ranges. The method combines both RTK GPS and ADCP technologies for the simultaneous measurement of water levels and velocities along repeated boat transects, allowing fast data acquisition over wide river sections and under rapidly changing conditions. The reconstruction of continuous and synoptic fields is made by interpolation. Simplifying assumptions about data stationarity and/or homogeneity are avoided by adapting the interpolation procedures to the shape and distribution of t...

We investigate the performance of a meshless method for the numerical simulation of depth-averaged turbulence flows. The governing equations are shallow water equations obtained by depth averaging of the full Reynolds equations including bed frictions, eddy viscosity, wind shear stresses, and Coriolis forces. As a double-phase closure turbulence model, we consider the depth-averaged kmodel. A truly meshless numerical method based on radial basis functions is employed to obtain an accurate approximation to the solution of the model. We validate the algorithm on a linear shallow water problem where analytical solutions are available. Numerical results are also compared with experimental data for a backward-facing flow problem. Furthermore, we test the method on a practical problem by simulating tidal flows in the Strait of Gibraltar. The main focus is to examine the performance of the meshless method for complex geometries with irregular bathymetry. The obtained results demonstrate its ability to capture the main flow features. Y. ALHURI ET AL. than water waves. For instance, the shallow water equations have applications in environmental and hydraulic engineering such as tidal flows in an estuary or coastal regions, rivers, reservoir, and open channel flows. Such practical flow problems are not trivial to simulate because the geometry can be complex, and the topography tends to be irregular. In addition, most of water free-surface flows encountered in engineering practice are turbulent characterized by: (i) highly unsteady features such that time series of the flow field at any point in the computational domain would appear random to an observer unfamiliar with these flows; (ii) appearance of a great deal of vorticity in which vortex stretching is one of the principal mechanisms by which the intensity of turbulence is increased; (iii) reduction of the velocity gradients due to the action of viscosity, which reduces the kinetic energy of the flow, that is, mixing is a dissipative process, and the lost energy is irreversibly converted into internal energy of the water; (iv) existence of repeatable coherent structures and essentially deterministic events that are responsible for a large part of the mixing; and (v) turbulent flows fluctuate on a broad range of length and time scales. This property makes direct numerical simulation of turbulent flows very difficult. It should also be stressed that turbulent flows contain variations on a much wider range of length and time scales than laminar flows. However, the random component of turbulent flows causes these events to differ from each other in size, strength, and time interval between occurrences, making their analysis very difficult. Despite that they are similar to the laminar flow, the equations describing turbulent flows are usually much more difficult and computationally demanding to solve. Considering the usual length scales in engineering practice, and the small kinematic viscosity of water, in most cases, the Reynolds number is large enough in order to consider the flow as fully turbulent. Even in the simplest situations of river flow, we can observe small eddies that appear and disappear with an apparently chaotic movement, showing the complexity of turbulent motion. In coastal regions, large eddies often occur because of the separation of the flow past a headland, a breakwater, or an island. These eddies are very important in environmental engineering, and they may influence the solute and sediment trapping.

We investigate the performance of a meshless method for the numerical simulation of depth-averaged turbulence flows. The governing equations are shallow water equations obtained by depth averaging of the full Reynolds equations including bed frictions, eddy viscosity, wind shear stresses, and Coriolis forces. As a double-phase closure turbulence model, we consider the depth-averaged kmodel. A truly meshless numerical method based on radial basis functions is employed to obtain an accurate approximation to the solution of the model. We validate the algorithm on a linear shallow water problem where analytical solutions are available. Numerical results are also compared with experimental data for a backward-facing flow problem. Furthermore, we test the method on a practical problem by simulating tidal flows in the Strait of Gibraltar. The main focus is to examine the performance of the meshless method for complex geometries with irregular bathymetry. The obtained results demonstrate its ability to capture the main flow features. Y. ALHURI ET AL. than water waves. For instance, the shallow water equations have applications in environmental and hydraulic engineering such as tidal flows in an estuary or coastal regions, rivers, reservoir, and open channel flows. Such practical flow problems are not trivial to simulate because the geometry can be complex, and the topography tends to be irregular. In addition, most of water free-surface flows encountered in engineering practice are turbulent characterized by: (i) highly unsteady features such that time series of the flow field at any point in the computational domain would appear random to an observer unfamiliar with these flows; (ii) appearance of a great deal of vorticity in which vortex stretching is one of the principal mechanisms by which the intensity of turbulence is increased; (iii) reduction of the velocity gradients due to the action of viscosity, which reduces the kinetic energy of the flow, that is, mixing is a dissipative process, and the lost energy is irreversibly converted into internal energy of the water; (iv) existence of repeatable coherent structures and essentially deterministic events that are responsible for a large part of the mixing; and (v) turbulent flows fluctuate on a broad range of length and time scales. This property makes direct numerical simulation of turbulent flows very difficult. It should also be stressed that turbulent flows contain variations on a much wider range of length and time scales than laminar flows. However, the random component of turbulent flows causes these events to differ from each other in size, strength, and time interval between occurrences, making their analysis very difficult. Despite that they are similar to the laminar flow, the equations describing turbulent flows are usually much more difficult and computationally demanding to solve. Considering the usual length scales in engineering practice, and the small kinematic viscosity of water, in most cases, the Reynolds number is large enough in order to consider the flow as fully turbulent. Even in the simplest situations of river flow, we can observe small eddies that appear and disappear with an apparently chaotic movement, showing the complexity of turbulent motion. In coastal regions, large eddies often occur because of the separation of the flow past a headland, a breakwater, or an island. These eddies are very important in environmental engineering, and they may influence the solute and sediment trapping.

The mechanics of the oblique impingement of an axisymmetric jet have been investigated. The kinematic constraint of no penetration requires the jet to spread and/or to deflect vertically in order to provide a sufficient cross sectional area for the mass flux. The selection between these two effects is established by the dynamical effects represented in the three-dimensional momentum equation. The velocity field, as expressed by the convective acceleration of the mean flow is primarily balanced by the three-dimensional pressure distribution above the plate and tailored by the Reynolds stress distribution. It is shown that an alternative description of the pertinent phenomena may be constructed by considering the vorticity transport equation. The gradients of the (easily measured) two-dimensional surface pressure field are source terms for the lateral and longitudinal vorticity components and the azimuthal vorticity structure in the approaching jet is reoriented to create a deformation in the isotach pattern which is characteristic of secondary flows.

Duxbury Beach is a retrograding barrier system located along the South Shore of Massachusetts Bay. The barrier fronts a large embayment consisting of a broad supratidal marsh in the northern sector grading to intertidal flats and open water to the south. Radiocarbon dates indicate that the barrier began forming sometime prior to 3,700 14 C years BP. The paucity of sediment combined with rising sea level have produced a relatively low barrier ranging in width from 95 to 285 m. The foredune is discontinuous and storm washovers are common. Historical maps and coastal charts indicate the presence of several former tidal inlets along the length of the barrier, although none exist today. Ground-Penetrating Radar (GPR) surveys suggest a minimum of 18 paleo-inlets along the barrier as indicated by large-scale channel cutand-fill structures. Former inlet channels range from 60 to 285 m in width and are typically 3 to 6 m deep. The ephemeral character of the inlets and their diminutive size are a product of their inability to capture a significant portion of the bay tidal prism. Seven channel fill patterns were documented in the GPR records; the three major types include prograded, conformable, and complex. The patterns of subsurface reflectors reveal that former inlet channels infilled by a variety of processes including simple spit extension from one or both sides and channel aggradation through landward sediment transport.

Cross-sectional gradients in water levels and velocities play a determining role in the circulation dynamics of tidal rivers and estuaries. Documenting and analyzing their variability throughout a tidal cycle require observations with high spatial and temporal resolution. A survey strategy and a data analysis procedure have been designed to obtain continuous and synoptic water level and velocity fields over a tidal cycle, along 13 cross-sections of the St. Lawrence fluvial estuary dominated by large tidal ranges. The method combines both RTK GPS and ADCP technologies for the simultaneous measurement of water levels and velocities along repeated boat transects, allowing fast data acquisition over wide river sections and under rapidly changing conditions. The reconstruction of continuous and synoptic fields is made by interpolation. Simplifying assumptions about data stationarity and/or homogeneity are avoided by adapting the interpolation procedures to the shape and distribution of t...

The interaction of a stratified flow with an isolated topographic feature can introduce numerous disturbances into the flow, including turbulent wakes, internal waves, and eddies. Measurements made near a "bump" east of Race Rocks, Vancouver Island, reveal a wide range of phenomena associated with the variable flow speeds and directions introduced by the local tides. Upstream and downstream flows were observed by placing two acoustic Doppler current profilers (ADCPs) on one flank of the bump. Simultaneous shipboard ADCP surveys corroborated some of the more striking features. Froude number conditions varied from subcritical to supercritical as the tidal velocities varied from 0.2 to 1.5 m s Ϫ1 . During the strong ebb, when the moored ADCPs were located on the lee side, a persistent full-water-depth lee wave was detected in one of the moored ADCPs and the shipboard ADCP. However, the placement of the moorings would suggest that, by the time it appears in the moored ADCP beams, the lee wave has been swept downstream or has separated from the bump. Raw ADCP beam velocities suggest enhanced turbulence during various phases of the tide. Many of the three-dimensional flow characteristics are in good agreement with laboratory studies, and some characteristics, such as shear in the bottom boundary layer, are not.

Applying a two-dimensional (2D) divergence-free (DF) interpolation to a one-person deployable unmanned underwater vehicle's (UUV) noisy moving-vessel acoustic Doppler current profiler (MV-ADCP) measurements improves the results and increases the utility of the UUV in tidal environments. For a 3.5-h MV-ACDP simulation that spatially and temporally varies with the M 2 tide, the 2D DF-estimated velocity magnitude and orientation improves by approximately 85%. Next the 2D DF method was applied to velocity data obtained from two UUVs that repeatedly performed seven 1-h survey tracks in Bear Cut Inlet, Miami, Florida. The DF method provides a more realistic and consistent representation of the ADCP measured flow field, improving magnitude and orientation estimates by approximately 25%. The improvement increases for lower flow velocities, when the ADCP measurements have low environmental signal-to-noise ratio. However, near slack tide when flow reversal occurs, the DF estimates are invalid because the flows are not steady state within the survey circuit.

A 2D divergence free interpolator is presented which is demonstrated to give more realistic values between sparse velocity data than interpolating velocity components independently. The interpolator enforces physical dependence between the velocity components by ensuring mass is conserved. Tests using data for a synthetic eddy show that independent interpolation of components can give unrealistic velocities between widely spaced data. However divergence free interpolation can reproduce the eddy almost as well with sparse data as with dense data. In the synthetic tests the divergence free Radial Basis Function (RBF) interpolator performed as well as, or better than, Optimal Interpolation. A significant advantage of the "Greedy Fit" RBF interpolator implemented here is the small number of coefficients required to describe the interpolating surface. For large data sets this gives the interpolator a significant computational advantage over techniques, like Optimal Interpolation, which require one coefficient per data point. The RBF's economy of parameters and imposing physics with the divergence free constraint makes RBF interpolation of sparse data much more resistant to following the noise. The 2D divergence free interpolator can be used to interpolate geostrophic velocities or the horizontal transport of high frequency flows such as tidal currents. Tests with data from the Local Dynamics Experiment moorings and from moving vessel ADCP measurements of tidal flow show the divergence free interpolator is better able to reproduce data left out of the interpolation than interpolating velocity components independently.

Acoustic Doppler Current Profiler measurements from moving vessels have recently been used to obtain detailed observations of the spatial patterns of tidal flows, as well as patterns of vorticity and dynamical terms. Developments in Radial Basis Function interpolation theory are demonstrated to significantly improve the quality of the tidal velocity field extracted from the measurements using thin plate splines. These include placing centers at data locations, enforcing "side conditions" on the solution and using higher order splines. For tidal flows with a scale less than a few kilometers, the differentiability of RBFs can be exploited to fit the streamfunction directly to the measurements. This ensures the observed tidal velocity field satisfies mass continuity. Enforcing mass continuity is demonstrated to significantly improve the ability of the splines to interpolate across wide gaps between vessel tracks. Extraordinarily detailed ADCP measurements of the tidal streamfunction within Bluff Harbour, NZ, reveal the stagnation streamline which separates a 200m wide flood tidal jet from an associated 400m diameter eddy. The stagnation streamline clearly shows that the eddy gains its fluid and vorticity from inshore of the jet's vorticity maximum. The eddy forms at 04:45 hours before high tide, grows in spiral fashion, and becomes isolated from the jet 02:30 hours before high tide, after which its vorticity rapidly decays.

Landmark placement is crucial in manual demarcation and registration of anatomical structures, registration of different image modalities (i.e. MRI/CT), labeling training data for lip and face principal component models, training for neural networks, and signal interpolation to name some applications. Although landmark placement at curvature and coordinate extrema (e.g. corners of the mouth, lowest point on the lower lip) is fairly unambiguous, the placement of point land- marks along a linear contour is subjective. Unfortunately the user’s choice of landmark placement determines the quality of the resulting registration. In this paper, we present an algorithm to remove these undesired degrees of freedom by re- placing landmarks along the contour. Ambiguous landmarks are moved so as to minimize a thin plate spline energy while constraining the landmarks to the originally specified contour. The resulting landmark placement results in a smoother reg- istration while still interpolating the contours and fixed landmarks. The results show that the ambiguity of manual landmark placement along contours does affect the smoothness of the interpolated registration, and that significantly smoother inter- polations can be achieved using our approach. This procedure may also benefit other applications employing landmarks by eliminating unintended curvature (variation) from the landmark data.

Landmark placement is crucial in manual demarcation and registration of anatomical structures, registration of different image modalities (ie MRI/CT), labeling training data for lip and face principal component models, training for neural networks, and signal interpolation to name some applications. Although landmark placement at curvature and coordinate extrema (eg corners of the mouth, lowest point on the lower lip) is fairly unambiguous, the placement of point landmarks along a linear contour is subjective. ...

1] A three-dimensional ocean circulation model is used to study the barotropic tidal circulation and nonlinear tidal dynamics in Lunenburg Bay, Nova Scotia. The model performance is first assessed using the observed bottom pressures and currents made in Septembers of 1991 and 2003. The model results reproduce reasonably well the observed tidal circulation in the study region. The simulated tidal circulation is dominated by the semidiurnal (M 2 ) tide and an intense jet-like flow through a narrow channel connecting Lunenburg Bay and two shallow coves. To demonstrate the importance of nonlinear tidal dynamics in the region, the first two harmonics of M 2 (i.e., M 4 and M 6 ) are computed from the model results forced by the M 2 tide at the model open boundaries. Both M 4 and M 6 are relatively large in western Lunenburg Bay and vicinity, indicating the importance of the nonlinear tidal dynamics over these areas. To quantify the role of various nonlinear terms in generating the intense jet and associated residual flows in the region of the jet, both transient and tidally averaged (time mean) momentum equations are examined. The transient and time mean momentum balances demonstrate that the nonlinear interaction of the tidal currents with local bathymetry is balanced primarily by the horizontal pressure gradients, momentum advection, and dissipation. The Coriolis effect plays a minor role in the study region.

We investigate the performance of a meshless method for the numerical simulation of depth-averaged turbulence flows. The governing equations are shallow water equations obtained by depth averaging of the full Reynolds equations including bed frictions, eddy viscosity, wind shear stresses, and Coriolis forces. As a double-phase closure turbulence model, we consider the depth-averaged kmodel. A truly meshless numerical method based on radial basis functions is employed to obtain an accurate approximation to the solution of the model. We validate the algorithm on a linear shallow water problem where analytical solutions are available. Numerical results are also compared with experimental data for a backward-facing flow problem. Furthermore, we test the method on a practical problem by simulating tidal flows in the Strait of Gibraltar. The main focus is to examine the performance of the meshless method for complex geometries with irregular bathymetry. The obtained results demonstrate its ability to capture the main flow features. Y. ALHURI ET AL. than water waves. For instance, the shallow water equations have applications in environmental and hydraulic engineering such as tidal flows in an estuary or coastal regions, rivers, reservoir, and open channel flows. Such practical flow problems are not trivial to simulate because the geometry can be complex, and the topography tends to be irregular. In addition, most of water free-surface flows encountered in engineering practice are turbulent characterized by: (i) highly unsteady features such that time series of the flow field at any point in the computational domain would appear random to an observer unfamiliar with these flows; (ii) appearance of a great deal of vorticity in which vortex stretching is one of the principal mechanisms by which the intensity of turbulence is increased; (iii) reduction of the velocity gradients due to the action of viscosity, which reduces the kinetic energy of the flow, that is, mixing is a dissipative process, and the lost energy is irreversibly converted into internal energy of the water; (iv) existence of repeatable coherent structures and essentially deterministic events that are responsible for a large part of the mixing; and (v) turbulent flows fluctuate on a broad range of length and time scales. This property makes direct numerical simulation of turbulent flows very difficult. It should also be stressed that turbulent flows contain variations on a much wider range of length and time scales than laminar flows. However, the random component of turbulent flows causes these events to differ from each other in size, strength, and time interval between occurrences, making their analysis very difficult. Despite that they are similar to the laminar flow, the equations describing turbulent flows are usually much more difficult and computationally demanding to solve. Considering the usual length scales in engineering practice, and the small kinematic viscosity of water, in most cases, the Reynolds number is large enough in order to consider the flow as fully turbulent. Even in the simplest situations of river flow, we can observe small eddies that appear and disappear with an apparently chaotic movement, showing the complexity of turbulent motion. In coastal regions, large eddies often occur because of the separation of the flow past a headland, a breakwater, or an island. These eddies are very important in environmental engineering, and they may influence the solute and sediment trapping.