Dissertations / Theses on the topic 'Acoustic Doppler Current Profiler (ACDP)'

A rating curve provides a functional relationship between water height (i.e. stage) and discharge at a specified cross-section in a river. Used in combination with a time series of stage, rating curves become one of the central components for generating continuous records of streamflow. Since developing and maintaining rating curves can be time consuming, hydraulic models have shown potential to reduce the effort required for developing rating curves. A central challenge with modeling procedures, however, is the acquisition of accurate stream channel and floodplain topography. From this perspective, this thesis focuses on the real-world application of close-range remote sensing techniques such as laser-based ranging technologies (i.e. Light detection and ranging or LiDAR) or acoustic based ranging technologies (i.e. acoustic Doppler current profiler or ADCP) to capture topographic information for hydraulic modeling applications across various spatial scales. First, a review of the current LiDAR literature was carried out to identify potential ways to take full advantage of these novel data and technologies in the future. This was followed by four interconnected studies whereby: (i) a low-cost custom laser scanning system was designed to capture grain size distributions for a small stream; (ii) synthetically thinned airborne laser scanning (ALS) data was applied in a physically-based hydraulic modelling framework to develop rating curves; (iii) low-resolution national-scale ALS was coupled with ADCP bathymetry to be used in conjunction with a hydraulic model to develop rating curves; and (iv) the impact of measurement uncertainties on generating rating curves with a hydraulic model were investigated. This thesis highlights the potential of close-range remote sensing techniques for capturing accurate stream channel topography and derive from these data, the necessary parameters required for hydraulic modeling applications.<br>En avbördningskurva tillhandahåller ett funktionellt förhållande mellan vattendjup (dvs. vattenstånd) och flöde vid ett specifikt tvärsnitt i ett vattendrag. Avbördningskurvan blir en central komponent för generering av kontinuerliga tidsserier av vattenföring från tidsserier av vattenstånd. Eftersom det är tidskrävande att utveckla och underhålla avbördningskurvor erbjuder hydrauliska modeller attraktiva möjligheter att minska den insats som krävs för att utveckla avbördningskurvorna. En central utmaning för sådana modelleringsförfaranden är emellertid tillgången till noggrann topografidata av strömfåran och de omgivande stränderna. Den här avhandlingen fokuserar på tillämpningen av fjärranalystekniker för avståndsmätning på nära håll, såsom laserbaserade teknik (dvs. Light detection and ranging eller LiDAR) och akustisk baserat teknik (dvs. acoustic Doppler current profiler eller ADCP), för att fånga topografisk information för hydraulisk modellering av vattendrag i olika rumsliga skalor. Först presenteras en litteraturstudie av den nuvarande LiDAR-litteratur för att identifiera potentiella sätt att dra full nytta av dessa nya data och tekniker i framtiden. Detta följs av fyra sammanlänkade studier: (i) tillämpning av ett lågkostnads-laseravsökningssystem för att fånga kornstorleksfördelningar i ett litet vattendrag, (ii) syntetiskt förtunnad flygburen laserskanningsdata (ALS) applicerad i en fysiskt baserad hydraulisk modell för att utveckla avbördningskurvor, (iii) lågupplösta ALS från Svensk nationell höjdmodell kopplade med ADCP-batymetri för att ta fram en avbördningskurva med en hydraulisk modell, och (iv) undersökning av effekterna av osäkerheter på mätdata för att generera avbördningskurvor med en hydraulisk modell. Denna avhandling belyser potentialen för fjärranalystekniker för avståndsmätning på nära håll, för att fånga strömfårans exakta topografi och ifrån dessa data härleda de parametrar som krävs för hydrauliska modelleringstillämpningar.<br><p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.</p>

Approved for public release; distribution is unlimited.<br>Ship-mounted acoustic Doppler current profiler (ADCP) data are used to study regional ocean patterns around the biologically rich regions of the Archipielago de Colon (Galapagos Islands) and the Gulf of the Farallones to test our assumptions about the circulation derived primarily from hydrographic samples. West of the Galapagos, an equatorial undercurrent transporting 7 Sv was present in November 1993, which decelerated within 30 km of the archipelago, shoaled, and diverged with a strong deflection to the southwest. A method of removing tidal velocities from ADCP measurements by creating an empirical model of the tides and using it to predict and subtract the tides is described. It is shown that in the Gulf of the Farallones, a large number of observations, typically more than acquired on one cruise, are necessary to reduce tidal model error. Detided ADCP data are used to describe the circulation in the Gulf under various wind conditions. Over the continental slope, Surface-to-depth poleward flow is present throughout the year. During wind relaxations, poleward flow strengthens and warmer, fresher water is transported onshore

In the Spring of 2012, hydraulic data was collected to calibrate three types of discharge models: stage-discharge, single-regression and multi-regression index velocity models. Unsteady flow conditions were observed at the site (â H/â t = 0.75 cm/min), but the data did not indicate hysteresis nor variable backwater effects on the stage-discharge relation. Furthermore, when corrected with a datum offset (α) value of -0.455, the stage-discharge relation r2 was equal to 0.98. While the multiple regression index velocity models also showed high correlation (r2 = 0.98) values, high noise levels of the parameter index velocity (Vi) complicated their use for the determination of discharge. Because of its reliability, low variance and accessibility to students, the stage-discharge model [Q = 5.459(H-0.455)^2.487] was selected as the model to determine discharge in real-time for LEWAS. Caution should be used, however, when applying the equation to stages above 1.0m. The selected discharge model was applied to ADCP stage (H) data collected during three runoff events in July 2012. Other LEWAS models showed similar discharge values (coefficient of variation = 0.14) while the on-site weir also produced similar discharge values. Precipitation estimates for July 19 and 24 rain events over the Webb Branch watershed were derived from IDW interpolated rain data and rainfall-runoff analyses from this data yielded an average ratio of 0.23, low for the urbanized watershed. However, since the three LEWAS models were very similar, and the on-site weir showed a lower value to LEWAS, it was concluded that any error in the ratio would be attributed to the precipitation estimate, and not the discharge models developed in this study.<br>Master of Science

A seasonal and long-term analysis of the vertical structure of currents in the nearshore is conducted to determine the role of the wind in driving currents and consequently affecting littoral transport processes. Approximately ten years (January, 2002 – October, 2011) of nearshore current profiles are examined using the data collected with an Acoustic Doppler Current Profiler (ADCP) installed off of Spessard Holland North Beach Park located in Melbourne Beach, Florida. Additionally, wind data collected with a directional anemometer from September, 2002, until October, 2008, are used to further characterize the long-term hydrodynamic forcing. With the shoreline oriented nominally 17o west of magnetic north, both the current profiles and the wind vectors have been rendered into longshore and cross-shore components. The water level record from a NOAA tide station located at the Trident Pier at nearby Port Canaveral is utilized in establishing the water depth and conditioning the data for statistical analysis. Monthly mean vertical profiles reveal that during the winter months the surface currents are usually toward the south, and toward the north in the summer. In spring and fall, they are mixed, demonstrating a clear seasonality in both direction and intensity of the longshore current. Subjecting the longshore and cross-shore current data to Empirical Orthogonal Function Analysis reveals that the first spatial Eigenfunction accounts for more than 98% of the variability in the vertical profile of the longshore current, and more than 86% of the variability in the profile of the cross-shore current. However, there is a rotation of the current to the right (clockwise) with the rotation angle increasing and the variance decreasing with depth below the surface. The spiral structure of the water column follows a surface Ekman veering, but for very shallow water. The upper layer of the current is almost aligned with the direction of the wind. Monthly correlations between 2-hour average time series of longshore current and 2-hour average time series of wind speed reveal the seasonal patterns of the wind and longshore current in which the upper layer of the water column is highly correlated with the longshore component of the wind speed for most of the year and slightly less correlated for the lower layer of the water column. Most importantly, on average, wave height (Hmo) is larger when the longshore current is heading to the south (Hmo=0.95 m) than when the current is going to the north (Hmo=0.73 m). Additionally, there is a stronger correlation between southerly directed currents and incident wave energy flux than northerly directed currents and wave energy flux. These results indicate that the net long-term north-to-south sediment transport known to characterize the region is heavily influenced by wind-driven currents.

碩士<br>國立臺灣大學<br>工程科學及海洋工程學研究所<br>105<br>Although Taiwan has abundant rainfall, there are lots of typhoons. And the relationship of the terrain is not ideal. It is important for sustainable development the water resources, so the flow measurement plays an important role. To know the flow before, we must know the flow rate. There are lots of research institutions to use foreign instruments in Taiwan. It called Acoustic Doppler Current Profiler (ADCP). It not only can measure the terrain of bottom, but the velocity of the flow. The hope of this paper is developing the system of the instrument initially. Acoustic Doppler Current Profiler is widely used in the marine and inland rivers. Ultrasound is non-invasive, non-destroyed, high security, and attenuated lower than optical methods, so it is frequently applied to underwater measurement. The experiment of this paper is using the narrow band method to calculate Doppler frequency shift, and to use the towing sink which is in the Department of Engineering Science and Ocean Engineering, NTU to verify the flow rate and error. The trailer of the towing tank moving will cause relative velocity to the water. It can analyze and verify flow rate. In terms of hardware, twenty-five millimeters and fifty millimeters of ultrasonic transducer and dock which is fitting the experiment are made in the laboratory. Protect the instrument from damage, and isolate received and emissive signal, this paper also used the limit isolation circuit board which is made in the laboratory. Digital oscilloscopes, function generator, power amplifier, and ultrasonic pulser/receiver are employed in the experiments. After bandpass filtering, quadrature demodulation, and low pass filtering, the Doppler frequency shift is calculated with power spectral density. Finally, using Doppler principle to get the flow velocities. Verify the results between experimental and actual values.

碩士<br>國立中興大學<br>土木工程學系<br>84<br>Abstract In general, rivers are steep and rapid in Taiwan. It is hard to measure the flow discharges during the medium and high flow stages.These data, however , are very important for the regulation of rivers and the water resources planning. To overcome the problem, this research used an acoustic doppler profiler ( ADP ) and Chiu's discharge theorem to more efficiently measure the medium and high flows. Both ADP and ADCP ( accoustic doppler current profiler) were calibrated in a tow tank based on the concept of relative motion. In addition, ADP were installed in a 300-pound lead fish and used to measured the flow discharges inthree rivers in the central region of Taiwan. The results of the tests indicated that the new equipment were fairly accurate except the regions near the channel bottom and the water surface due to the " side-lobe " effect and the limitation of " blanking distance ", respectively. In order to check the applicability of Chiu's discharge theorem, a set of alluvial channel data collected at Colorado State University were analyzed. It was found that the ratio of the cross-sectional average velocity to maximum velocity were relatively stable for wholly turbulent flow with rough bed, and it decreased slightly with an increase of the channel roughness. For the Chien-Fong and Nan-Pei Tong hydrological stations, both the ratio of and Y-axis ( the vertical passing through the maximum velocity of the cross section ) were reasonably stable. With application of both the Chiu's discharge theorem and the ADP, these two stations can be considered as an automatic hydrologic stations for discharge measurement in the future. As regareds Tong-Tou hydrological station, both the ratio of and the Y-axis varied with flow stage during the low flow, and additional data for medium and high flow need to be collected for further anysis in the future.

In this study, a PortMap Ocean Surface Current Radar operating in the VHF band was used in conjunction with a seabed mounted Acoustic Doppler Current Profiler to obtain measurements of current velocity through the Lido channel to the Venice Lagoon. Current flow data were obtained over a six week period from both instruments. These data, together with additional data obtained from tide gauges and wind speed data from weather stations have been used to develop techniques for producing the measurements required to obtain the mass transport of water through the inlet. The combination of data from these two different instruments was used to overcome the limitations of each technology in obtaining a complete estimation of mass transport through the inlet. Seabed mounted ADCPs only provide current measurements for a single geographical point, and are unable to measure the surface current due to side-lobe ringing within a few metres of the surface. It is for this reason that a second technology, the surface current radar was used to measure the current across the surface of the channel. For the PortMap Ocean Surface Current Radar operating in the VHF Band (152.2 MHz) this represents a depth weighted average measurement in the upper 15.7 cm of the water column. The PortMap radar systems used in Venice produced data that were generally of a very poor signal-to-noise ratio. This was determined to be caused by a hardware fault present in the PortMap radar affecting the range resolution. Although this resulted in insufficient radar coverage of the channel required to produce an evaluation of mass transport, techniques were developed to produce the secondary data required for this purpose. The analysis software was modified to reflect the change in range resolution, enabling high resolution, short-range current vector maps to be produced for the regions surrounding each radar station. During the deployment, a turbid water plume was observed entering on the Sabbioni side of the inlet while the tide continued to ebb on the Lido side of the inlet. The high resolution vector current maps produced were sufficient to observe this interesting current dynamic. These measurements show that during an outgoing tide with a strong ebb tidal stream on the Lido side of the channel, water begins to flow into the channel on the Sabbioni side of the channel. This current dynamic has obvious implications for the transport of sediment from the neighbouring Cavallino beach into the inlet, and into the Venice Lagoon.

The measurement of total suspended solids (TSS) concentrations through water quality monitoring programs is laborious, costly, and time-intensive. Winter conditions further hinder water quality monitoring programs. The use of Acoustic Doppler Current Profilers (ADCPs) is currently being explored as a surrogate for estimating total suspended solids concentrations. TSS concentration and ADCP measurements were collected during the winter at the Lower Nelson River and the Red River such that ADCP backscatter data could be calibrated to TSS concentrations. Different calibration schemes were pursued, some involving flow parameters determined from ADCP data, in order to accurately model the data. Due to limited ranges in the data, further TSS concentration and ADCP measurements were taken during the open water period. Calibrations were achieved with varying degrees of accuracy, however the they failed to perform well beyond the ranges for which they were developed.

We examine currents and relative zooplankton scattering strengths measured with a vessel-mounted RD Instruments 150 kHz acoustic Doppler current profiler (ADCP) over the southwest Vancouver Island continental margin. Raw ADCP signal strengths are converted into relative zooplankton backscatter intensities using a method of residuals computed from average linear fits to depth profiles, which removes most system-dependent effects. An absolute calibration is not feasible without coincident net tows and a record of system characteristics. The problem of side-lobe contamination of near-bottom zooplankton backscatter estimates is given considerable attention and an objective method is developed to eliminate erroneous backscatter values. Ship-referenced water velocities are converted to absolute (earth-referenced) currents using bottom-tracking measurements of ship velocities. Methods of calculating absolute currents using ship velocities estimated from the change in (GPS) ship position are also examined. It is shown that the GPS positional errors of « ± 300 m lead to velocity errors that are comparable to the currents. Only when bottom-tracking is available are absolute currents reliable. The methods developed to process the data are applied to ADCP data collected in June 1993 over the southwest Vancouver Island continental margin. The currents and relative zooplankton scattering strengths are examined over a 20 hour period along a 14 km survey line which spans the shelf break. Zooplankton concentrations occupied the upper 50 m over the shelf and slope both day and night. Aggregations of scatterers were present over the shelf break at depths of 150-200.m during the day, and migrated to the surface waters at sunset. Mean upwards swimming speeds were 1-1.5 cm/s. Offshore flow and vertical shears of the order of 10⁻³ s⁻¹ on the shelf were correlated with horizontal movements of zooplankton, indicating that the distribution of zooplankton over the shelf and slope was influenced significantly by advection. A strong scattering layer with backscatter intensities 100 times higher than normal surface intensities was advected into the survey area over the shelf a few hours before sunrise on June 30th 1993, and underwent downwards migration just prior to sunrise. Mean downwards swimming speeds were 3-4 cm/s. A southwestward flowing shelf-break current was observed in the upper 50 m with speeds of 15-20 cm/s. The contribution of tidal flows to the net current is determined and is found to be consistent with the predictions of Foreman's (1990) finite-element barotropic tidal model. The ADCP data taken in June, 1993 are examined along eight 100 km long survey lines perpendicular to the coast of Vancouver Island. The eight survey lines span the region from the mouth of Juan de Fuca Strait to the mouth of Barkley Sound. Zooplankton concentrations occupied the upper 50 m over the shelf and slope both day and night. Aggregations of scatterers were present over the shelf break at depths of 150-200 m during the day. A southwestward flowing shelf-break current was observed in the upper 50 m with speeds of 15-20 cm/s. An estuarine type flow was observed at the mouth of Juan de Fuca Strait, with strong (>30 cm/s) outflow in the upper 80 m and weaker landward flow below 80 m. These currents are consistent with previous measurements in the region. The ADCP data taken in June, 1993 are spatially averaged in order to characterize the summer mean zooplankton distribution and current pattern. Surface zooplankton concentrations were observed both day and night over the shelf and slope from Estevan Point to Juan de Fuca Canyon. High concentrations were found near the bottom along the shelf break from Estevan Point to Juan de Fuca Canyon. A southwestward flowing shelf break current with speeds of 15-20 cm/s was persistent along the shelf break from Estevan Point to Juan de Fuca Canyon. Surface outflow from Juan de Fuca Strait was observed to persist up to about 50 km seaward over the shelf. A counterclockwise flowing eddy with a radius of about 30 km was observed over Juan de Fuca Canyon. Current speeds associated with the eddy were strongest near the surface and diminished gradually with depth. Based on the limited data analyzed, it would appear that coastal ocean processes are too affected by high-frequency (tidal period) variability for ADCP surveys to provide synoptic views of the circulation and zooplankton biomass. However, this study demonstrates that the vessel-mounted ADCP is useful for observations of current velocity and zooplankton biomass distribution in confined spatial regions on diurnal time scales.

Dissertação de mestrado em Engenharia Eletrónica Industrial e Computadores<br>O objetivo deste trabalho é desenvolver um sensor acústico capaz de medir correntes marítimas. Este projeto surge da necessidade de recolher alguns dados de interesse marítimo com o objetivo de criar modelos de funcionamento dos ecossistemas. Neste projeto pretende-se colocar vários sensores georreferenciados, a diferentes profundidades, a fazer medições e a armazenar os dados respetivos. Este sensor será responsável por medir a velocidade da água que flui num determinado nó do sistema. Este deverá ser capaz de medir a intensidade da corrente e a direção independentemente da sua posição no espaço, necessitando por isso de um magnetómetro (bússola digital) para utilizar o norte geográfico como referência. O sensor de corrente marítima que é apresentado utiliza transdutores piezoelétricos ultrassónicos pretendendo com isso tornar o sistema mais fiável e com maior robustez devido à ausência de partes móveis. A propriedade dos ultrassons explorada neste trabalho para obtenção da velocidade da corrente é o tempo de voo. O tempo de voo é o tempo que um determinado sinal demora a propagar-se num determinado meio entre dois pontos. No desenvolvimento do sensor será estudado o formato da estrutura, a posição e a orientação dos transdutores, de forma a melhorar a qualidade das medições em diferentes condições. Tal deverá ter em conta a robustez, dimensões razoáveis e evitar fenómenos de turbulência no volume de água a ser medido. O processamento dos sinais enviados e recebidos pelos transdutores será executado por um circuito integrado capaz de executar rotinas de medição de tempo de voo e de temperatura. Esse circuito integrado irá comunicar com um microcontrolador que irá interpretar os tempos de voo e converter na velocidade do fluido. Para além da comunicação com este circuito integrado, o microcontrolador, terá que comunicar com um relógio de tempo real, para obtenção de uma referência temporal, com um cartão de memória, para armazenamento de dados num ficheiro e com um magnetómetro, para obter uma referência de orientação ao norte geográfico já que o sensor não estará fixo. Com vários sensores destes é possível entender fenómenos de transporte à escala costeira, graças aos dados que é possível obter com um instrumento de medição desta escala.<br>The objective of this work is to develop an acoustic sensor capable of measuring sea currents. This project arises from the need to collect some data of maritime interest with the aim of creating models for the functioning of ecosystems. In this project, we intend to place several georeferenced sensors at different depths to make measurements and store the respective data. This sensor will be responsible for measuring the velocity of the water flowing in a particular node of the system. It should be able to measure the intensity of the current and direction independently of its position in space, thus necessitating a magnetometer (digital compass) to establish geographic north as a reference. The marine current sensor which is shown utilizes ultrasonic piezoelectric transducers in order to make the system more reliable and more robust due to the absence of moving parts. The property of the ultrasound explored in this work to obtain the velocity of the current is the flight time. Flight time is the time that a given signal takes to propagate in a certain medium between two points. In the development of the sensor will be studied the structure format, the position and the orientation of the transducers, in order to improve the quality of the measurements under different conditions. This should take into account the robustness, reasonable dimensions and avoid phenomena of turbulence in the volume of water to be measured. The processing of the signals sent and received by the transducers will be performed by an integrated circuit capable of performing flight time and temperature measurement routines. This integrated circuit will communicate with a microcontroller that will interpret flight times and convert to fluid velocity. In addition to communicating with this integrated circuit, the microcontroller must communicate with a real-time clock, to obtain a time reference, with a memory card, to store data in a file and with a magnetometer, to obtain a reference geographic north since the sensor will not be static. With several sensors of these it is possible to understand transport phenomena to the scale of the coast, thanks to the data that can be obtained with a measurement instrument of this scale.