This paper details a method to compute absolute water velocity profiles from glider-based acoustic Doppler current profiler (ADCP) measurements based on the "shear method" developed for lowered ADCPs. The instrument is a 614-kHz Teledyne RDI ADCP integrated into the body of a Teledyne Webb Research Slocum Glider. Shear is calculated from velocity measurements and averaged over depth intervals to create a dive-averaged shear profile. Absolute velocities are computed by vertically integrating shear profiles yielding relative velocity profiles and then referencing them to dive-average velocity measurements calculated from glider dead-reckoning and GPS. Bottom-track referenced velocities also provide absolute velocities when bottom-tracking is available, and can be applied to relative velocities, producing absolute velocity profiles through linear fitting. Data quality control is based on ADCP percent good measurements. Compass heading bias corrections are applied to the raw ADCP measurements before averaging shear profiles. Comparison between simultaneous, full-water column velocities referenced to dive-average currents and those referenced to bottom-track profiles, resulted in RMS error values of 0.05 m s⁻¹ for both north and east components. During open ocean deployments, the glider ADCP recorded velocities concurrent and proximate to vessel ADCP measurements in waters of similar thermal characteristics. The combined comparison analysis resulted in RMS error values ranging 0.08-0.31 m s⁻¹ and 0.06-0.21 m s⁻¹ for north and east components, respectively. / Graduation date: 2013

A study was made to evaluate how current measurementscould help to determine how particles from fish farms are dispersed. During sixweeks of the summer 2012, two different current measurements were conducted.One of them consisted of measurements each fifth minute at 5 m and 15 m atthree locations for 14-16 days each. The other consisted of profilemeasurements at each location at four times during the period of six weeks. Forthe current measurements two instruments (model RCM 9) were used. A two weekmeasurement can give enough data to make an evaluation of how the currents at alocation will transport litter from a fish farm. A longer probing time wouldhowever be desirable since the currents along the northern east coast of Swedenare mainly driven by factors that are changing during the year such as airpressure, temperature, precipitation etc. Water current measurements can be ofgreat help both when determining how particles from a fish farm is dispersedand also for governing authorities in the processes of both allowing new fishfarms and also when supervision of fish farms is needed.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Webster, Don; Committee Member: Sturm, Terry; Committee Member: Weissburg, Marc. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This study seeks to identify naturally occurring differences in the turbulent environment at a variety of field sites near the Skidaway Institute of Oceanography, in Wassaw Sound and surrounding bodies of water. The sites have previously been used to study predator-prey interactions. Velocity time records were recorded using acoustic Doppler velocimetry (ADV) probes at six sites on four days, with a total of 14 data sets. Differential estimate phase filtering was employed to identify erroneous velocity measurements. Less than 3% of the total samples were identified for any given data set with the exception of three sets that contained nonphysical banded bursts. Set mean velocity statistics were largely unaffected by phase filtration, while turbulent kinetic energy (TKE) was reduced in magnitude. Because the sites were exposed to waves, wave contributions to TKE and Reynolds shear stress were computed. Power spectral densities (PSDs) were computed for each velocity burst, and the contributions from wave-related and turbulent fluctuations were isolated. Wave components of TKE and Reynolds shear stress were computed. Wave contributions to turbulent characteristics for most sets were between 10-20% of the total value. Wave contributions to TKE were consistent but wave contributions to Reynolds shear stresses were irregular. Burst-average velocity statistics, TKE, Reynolds shear stress, and turbulence intensity (TI) were computed for each set. Large variability in turbulent characteristics was observed both temporally and spatially. Tidal influences were apparent as turbulent characteristics often reached absolute maximum values during the incoming or outgoing tides. No consistent trends were observed in relationships between the sites. The findings of the study emphasize the importance of applying data filtration to raw ADV data, suggest an order of magnitude of wave contributions in a particular tidal ecosystem, and demonstrate the inherent variability of turbulent characteristics. The study also illustrates the importance of considering multiple turbulence parameters for a give site, due to the lack of observed relationships between TKE, TI, and Reynolds shear stress. Further work is needed to determine if other parameters that are relevant from a flow characterization standpoint are also important ecologically.

Thesis (Ocean E)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1979. / Supervised by Ole Secher Madsen and William D. Grant. Includes bibliographical references (leaves 142-144).

Cette thèse s'inscrit dans le cadre des énergies renouvelables au sein du programme HARVEST du laboratoire LEGI, qui consiste à développer un concept d'hydrolienne de type Darrieus. L'hydrolienne peut être équipée d'un dispositif appelé carénage afin de transformer une portion plus grande de l'énergie cinétique contenue dans le courant d'eau en électricité. Les travaux présentés se sont focalisés sur ces systèmes de carénage, autour de trois axes : l'explication du principe de fonctionnement hydrodynamique du carénage, la quantification des performances de l'hydrolienne carénée et la mise en évidence des grandeurs géométriques clés du carénage permettant d'améliorer ou d'optimiser la performance du système. Toutes les études ont été réalisées à l'aide des calculs RANS 2D et des données expérimentales mises à disposition et, comparées aux résultats obtenus pour une hydrolienne non-carénée. / The general context of the present thesis is renewable energies within the HARVEST program initialized at LEGI laboratory, which consists in developing a Darrieus-type water current turbine (WCT). The WTC can be equipped with a channelling device which allows transforming a bigger amount of the kinetic energy contained in the flowstream into electricity. The present work is focused on the channelling devices. Studies concern three main topics: the explanation of the channelling device hydrodynamic functioning, the evaluation of the performance of the shrouded WCT and the revealing of the system geometrical parameters which allow its improvement or optimisation. All studies have been carried out by 2D RANS calculations and available experimental data, and have been compared to bare WTC results.