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Aiming at the estimation of Doppler shift factor in underwater acoustic communication, a new method based on current velocity measurement is proposed. By analyzing the relationship between current velocity and the Doppler shift factor, the calculation process of underwater acoustic communication system is simplified, the measurement method and ability of electromagnetic current meter is studied, and some on-site error sources are analyzed. The results indicate that the piecewise linear method can effectively characterize the measurement of electromagnetic current meter. Zero offset drift has to be modified frequently. The displacement effect is the main factor affecting the measurement results of the current meter, and the maximum indication error can be up to 10%.

This paper presents the design of the current meter showing results through a smartphone application, to measure the current for PEA pole-mouth distribution transformer on the low-voltage side. This tool can reduce the danger that may occur to the staff in high locations, as well as reduce working time. Base on the principle of the current transmitter measured the current of the overhead line, convert to the current signal from 4-20 mA. The current signals transmitter to the analog signal, this signal detected by ESP8266 mini-WiFi. Then processed into actual values compare with the standard clamp meter. The device can indicate the current value via WiFi communication on a smartphone, the current value that is measured has an error no more than 2.74% compared to the standard clamp meter.

The measurements of tidal currents in the ocean can be done by instruments deployed in the ocean, or by a moving research vessel carrying a current meter. The latter has the advantage of resolution of spatial structures of the flow field both in the vertical and in the horizontal. In an archipelago region where the bathymetry and geomorphology in general are complicated and tidal currents swift between islands, the measurements with either method can be challenging. Aimed at the resolution of eddies and the complicated flow structures, two ship-based surveys were conducted in the Zhoushan Archipelago region in summer of 2017 and summer of 2018. A 300 KHz acoustic Doppler current profiler (ADCP) was used in measuring the current velocity profile time series along a planned route around a selected island. We observed eddies and velocity field around small islands in the area with strong tides, narrow channels, dramatic change in depth, and strong velocity shears. Our preliminary analysis has provided interesting results. This report briefly summarizes the ongoing work done thus far. Basically, a few eddies were apparent on the leeward side of the island. These eddies were changing with tidal phase. Harmonic analysis allowed us to resolve both the tidal elevation from the depth data and tidal current from the velocity profile time series. The data are expected to be used in subsequent model validation for comprehensive numerical experiments on hydrodynamics including transport, dispersion, storm surge, and other related dynamical processes.

The paper aims at developing a simpler but more precise methodology for in situ determination of turbine discharge at small hydro power plants using the velocity-area method known as the current meter method. Simplifying the methodology for determining the turbine discharge rate in hydro-units in small hydro power plants will reduce the time required to perform in situ determinations but also reduce the costs required to carry out the in situ determination of the turbine discharge, the main parameter in determining the efficiency hydro-units which equips micro-hydro power plants MHPP and small hydro power plants SHPP.

China's Hainan network system 500kV AC submarine cable has the world's largest length and the second largest capacity in the world, with very important political and economic significance. The surface temperature of the power cable is estimated to calculate the internal conductor temperature and the current rating capacity. Firstly, the principle of testing is introduced, which is the principle of temperature testing of the optical cable bundled on the power cable surface using the Brillouin optical time domain reflectometer tester. Secondly, the power cable current rating experiment was designed. The power cable is bundled on the surface of the 10 meter optical cable. The BOTDA distributed temperature tester is attached to both ends of the power cable to monitor the power cable surface, record the surface temperature of the power cable, and route the power cable through cable heater. Use the power cable heat cycling test system to heat the power cable, the temperature of cable conductor is monitored by a thermocouple, and clamp current meter monitors the current rating capacity of the conductor, changes the regulation value of the through transformer, recording the temperature and load of the power cable conductor. Finally, this method of bundling the optical cable on the power cable surface was verified, which provided an experimental basis for submarine cable temperature monitoring.

The McLane Moored Profiler (MMP), developed from prototype vehicles conceived and constructed at the Woods Hole Oceanographic Institution, has been in operational use for nearly 20 years. The full-depth-capable MMP utilizes a traction drive system to propel itself vertically along a standard mooring cable and transport a single sensor suite through the water column (negating possible errors due to multiple sensor intercalibration). MMPs are commonly configured with a single-point current meter and a CTD (a variety of other sensors have also been interfaced); processed data yield repeated realizations of the ocean temperature, salinity and horizontal velocity profiles at order 1 m vertical resolution on deployments lasting sometimes 2 years or longer. Standard MMP battery capacity results in a profiling endurance typically around 800 km of total travel, with profiles distributed in time as the user specifies. Motivated by the twin goals of increasing profiling endurance and improving sensor data quality, a joint development project for the Articulating Profiler was undertaken by WHOI and MRL that reconfigures MMP components into a streamlined body able to orient into the relative three-dimensional incident flow. A series of dock tests below the WHOI pier refined the mechanical design of the AP, followed by a 10-month ocean deployment on the continental slope north of Cape Hatteras, N.C. in conjunction with the PEACH (Processes Driving Exchange Between the Shelf and Deep Ocean at Cape Hatteras) program. Results from these test deployments are presented and plans for further development discussed.

The purpose of this study is to estimate the discharge of Lesser Zab River in Taqtaq area, Iraq. Area - velocity method was used for measuring the discharge of the river, the cross section of the river was divided in to 38 elemental strips of equal width (b). Midsection method was used for determining the discharge in each elemental strip. In this study GPR (Ground Penetrating Radar) technique was used for measuring the depth of the river in Taqtaq area, current meter device was used for measuring the water velocity in different depths, 0.6d for shallow depths and 0.2d & 0.8d for deep waters. The results indicated that width of the river is 41 meter. The highest depth of the river is 3.4 meter, width of each sub-section is 2 meter, and on both sides of the river 1.5 meter is not considered for measurements. The average velocity in subsections ranges between 0.15 – 1.832 m/s., the minimum discharge is in sub section number 1 which is equal to 0.12m3/s and the maximum discharge is in sub section number 13 which is equal to 12.787 m3/s. The total discharge of the river is 99.29 m3/s.

This study investigates the capability of camera technology and Large Scale Particle Imaging Velocimetry (LSPIV) measurement techniques to access the sea surface velocity conditions in spatiotemporal dimensions in a tidal inlet, located in the southern North Sea. LSPIV shows reliable results for various applications in riverine and hydrographic studies, nonetheless LSPIV is up to date less prominent in offshore maritime studies. Characterized by high dynamic velocity ranges, changing water levels, waves and directions of flow within tidal cycles, the maritime domain implies varying boundary conditions compared to inland study areas. We present application possibilities, procedures as well as computer vision and data fusion approaches based on remote sensing in the oceanographic environment. Video data of the sea surface, observed from high-resolution visual camera, are analyzed for natural tracers within tidal cycles. Quality assessments were applied for prevailing environment conditions as well as concurrent observations with an Acoustic Doppler Current Profiler (ADCP) and current meter in the water column for hydrographic conditions. The LSPIV method showed reliable results for the fluctuation of water flow direction. Velocity mean magnitudes permitted to access surface flow for a dynamic range of 0.15–1.5 m/s. Comparing LSPIV and in situ measurements, we achieved deviations in the range of ± 0.5 m/s within a tidal cycle and with a good correlation (R2 = 0.82) given appropriate light conditions. The optical method applied here within offers a complementary alternative for modern environmental monitoring enabling space- and time-resolved hydrographic information for the oceanographic research domain.

This paper presents results on the development of a simplified low frequency magnetic field/harmonic current meter that is easy to construct. The device measures the intensity of the most significant harmonics fields and, indirectly, the harmonic currents. This device can be used as, and is conceived as, an educational tool, assisting students while learning signal processing, power quality and electromagnetic compatibility.

Purpose. A current meter based on the principle of electromagnetic induction is designed to register the current flowing in the lightning rod. The aim of the article is to describe the way of increasing the sensitivity. Methodology. The meter is used for measuring the current pulses with a rise time of 5 ns to 50 ns. If compared with other methods, meters based on the principle of electromagnetic induction have several advantages, such as simplicity of construction, reliability, low cost, no need in a power source, high sensitivity and absence of electrical contact. Also the meter responds to a narrow bandwidth and noise cannot penetrate into the electrical circuit, which is connected to the meter. Originality. Series connection of converters has the property of a long line when influenced by the pulses of the nanosecond range. The level of the transient response of the meter is calculated. The influence of parasitic parameters on the type of meter transient response is examined. The shown construction was not previously described. Practical value. The results of meter implementation are given. The design peculiarities of such measuring instruments are shown. Applying such a structure is only possible when measuring the nanosecond signals or less. Otherwise the property of a long line disappears.

This paper is a cautionary tale about replacement of a controller in a successful current meter when the previous controller became unavailable. The hardware changes required dealing with a new footprint and new voltages and these were done in 2014 and tested in 2015 but the revisions of the C code begun in 2015 have taken all of 2016 to reach the critical testing stage in July 2016 with reports of some final tests deferred until presentation of the paper in September.

We report on new calibration methods for picoammeters and low-current sources. The "Ultrastable Low-noise Current Amplifier" (ULCA) was used for the exemplary calibration of commercial state-of-the-art ammeter and current source instruments in the current range between 1 femtoampere and 1 microampere. The uncertainties achieved are compared with results obtained from two other calibration methods for small direct currents. It is shown that using the ULCA as calibrator allows achieving lower uncertainties together with the benefit of easier handling compared to alternative techniques. Also, the ULCA allows performing current meter and source calibrations between 1 femtoampere and 1 microampere with a single method., 2 pages, 1 figure

Considerable interests in recent years have been directed towards the study of various mechanical devices to draw up deep ocean water (DOW), particularly the air-lift artificial upwelling devices. However, one of the obstacles which limit their application in open ocean mariculture is the difficulty in estimating the flow rate in the upwelling pipe. Conventionally, the water flow rate in the upwelling pipe is measured by a electromagnetic flowmeter (EMF). However, the EMF can not withstand the pressure under the sea. In this study, a current meter based on accelerometer is designed. It aims to obtain relatively precise data of flow rate in pipe, which enables artificial upwelling devices to perform better in mariculture.

Ocean velocity in the Arctic is estimated using a three-axis acoustic travel-time current meter onboard an Ice-Tethered Profiler (ITP). The ITP is moored on an ice floe, with the current meter measuring velocity past the sensor as it profiles vertically through the water column along an inclined wire and translates horizontally with the motion of the overlying sea ice. Accurate estimates of ocean velocity rely on simultaneous estimates of instrument pitch, roll, and heading, the velocity at which the sensor crawls along the wire, and the velocity of the overlying sea ice. An inertial measurement unit is used to derive instrument pitch, roll, and heading from a three-axis flux-gate compass, accelerometer, and angle rate gyro. Instrument speed along the wire is derived from pressure as measured by the CTD. Hourly GPS fixes of the surface package are used to estimate ice velocity. Pre-deployment calibrations are preformed to determine magnetometer, accelerometer, pitch, roll, and heading biases. Post-deployment calibration parameters are determined to account for remaining biases. Post-deployment parameters are chosen so that there is no obvious bias related to wire angle, velocity estimates when the profiler is stationary versus moving, or upward versus downward profiles. These procedures are described as implemented for the second-generation velocity sensor deployed in the Arctic Ocean on five Ice-Tethered Profilers during 2013–2015.

After 2011 Tohoku-Pacific Ocean earthquake, Chubu Electric Power Co., Inc. has been voluntary addressing to build the tsunami observation network at Hamaoka nuclear power station mainly utilizing an ocean radar, the GPS-mounted Buoy, the submarine cabled real-time seafloor observatory system and a highly sensitive camera. The purpose of this study is to evaluate the basic usability of the VHF ocean radar through field observation in front of Hamaoka nuclear P/S, and to investigate short time variability of coastal currents under the natural condition for construction of tsunami warning system. High acquisition area of valid current data of the ocean radar varied from 13 to 17 km off the observation site in the radial direction, which suggests the maximum detection range of tsunami by the ocean radar in this sea area. The comparison of the current data by the ocean radar with the current meter resulted in the correlation coefficient of about 0.8 in radial direction, and the correlation improved after reducing the wind-driven effect by the multiple regression analysis with the wind data. As the temporal variability of coastal currents to 1-hour interval was almost about 5 to 10 cm/s, the current anomaly excited by tsunami greater than 10 cm/s seems to be detectable by the ocean radar in this area.

Underwater sensors of water flow share issues addressed independently by manufacturers. Power has become the most demanding concern since availability of cheap memory has removed data storage as the limit for self-contained current meters. Neither power nor memory is a limit with cabled observatory instruments but for autonomous installations, improvement in batteries is valuable but not sufficient. Power saving is more effective for extending deployment duration than improved batteries [1]. Fouling, by marine organisms or by corrosion, limits both cabled and autonomous instruments, degrading measurements for some modalities more than others. While there are active anti-fouling systems, most protections are passive with material selection and coatings the first line of defense. Upper ocean deployments, in the photic zone, are sometimes limited in duration by fouling with macro algae. Extending such deployment duration may require a second line of defense such as active scrapers or cutters. Traditional care for shallowly deployed current sensors involves divers to scrub transducers with abrasive pads. Below the photic zone bio fouling is less aggressive. Slippery coatings are now employed in some deployments where previously toxic coatings endeavored to prevent growth of animals and plants [2]. Plastic and titanium housings have made corrosion almost a problem of the past, although there are cost and other consequences that need to be considered [3].

The newly designed Instrument MTMI (Moored Turbulence Measuring Instrument) developed by OUC (Ocean University of China) had been deployed in the South China Sea from October 19, 2013 to February 10, 2014 at 21° 09.900′ N 117°42.031′ E and succeed to collect time series for about 115 days in 250-m-deep water. According to the requirements of turbulence measurement, the mechanical design was developed for turbulence observation platform to achieve stability and good flow tracking. By analyzing the pitch varying with flow speed, the results suggested that the platform satisfies the requirements of stability. Then, the heading of instrument compared with the flow direction measured by RCM (Recording Current Meter), and the two groups of data matched well which showed that our platform has a good ability to track the vibration of the flow direction. Finally, the power spectrum curves of shear signals and the theoretical Nasmyth spectrum also matched well and the rate of turbulence dissipation are 10−7W kg−1 approximately. In general, instrument mechanics were rationally designed and MTMI provided a good observation platform for the long-term turbulence measurements.

The currents measured by a SonTek Acoustic Doppler Current Profiler (ADCP) mounted on an Iver2 Autonomous Underwater Vehicle (AUV) are compared to those measured by a bottom-mounted Acoustic Wave and Current Meter (AWAC), taken as a reference, in an attempt to evaluate the AUV's performance as a current meter instrument. In October 2013, the AUV performed 3 short missions navigating over the AWAC at ∼1.5 m depth and ∼1.5 ms−1 velocity while profiling currents down to about 22 m depth, where the AWAC was mounted. The AUV spent about a 16% of mission time on the wavy surface, where its ADCP continued profiling. A 3D AUV currents data processing approach is used to compensate for AUV attitude and is validated by averaging entire mission data, showing absolute errors lower than 0.05 ms−1 for a large part of the depth range. An AUV data averaging time of 600 s yields horizontal velocity errors of about 0.07 ms−1 while the 90 s averaging time is found to be a good compromise between error (slightly larger than the one obtained with a 600 s time window) and temporal resolution. Results are promising but more testing in different environmental and operational conditions is needed to validate the AUV as a current meter.

This paper presents an evaluation of engineering and economic feasibility of micro-hydropower plant project. The studied site is located at Thanthong village, Mea-On district, Chiang Mai province. The engineering feasibility studies in this project are using 4 different methods of rate of water flow, which are the average runoff from streamflow gauging station, flow rate from floats method, flow rate from current meter and Manning equation. The experimental and calculation results at 100% flow rate for hydropower generation installed capacities for hydropower plant of each method are 86, 44, 54 and 181 kW, respectively. In addition, this hydropower plant can generate power at 349, 175, 218, and 786 MWh per year, respectively. In term of economy feasibility, Manning equation method has the highest Internal Rate of Return (IRR) at 58.74%, which is comparted with streamflow gauging station method has IRR only at 25.23%. Consideration results of IRR and electric energy, it can be concluded that the accuracy of flow rate is a significant factor for evaluation of hydropower project. The accuracy of data could be collected data for long period of time as using in streamflow gauging station, not just only one year period as using in Manning equation. Therefore, the streamflow gauging station method is an appropriated tool for using in feasibility study of micro-hydropower plant project.

Historically, current sensors have been calibrated and intercompared to determine their accuracy and to develop trust in the quality of their data collected. In a more mature technology, standards are established to quantify quality, trustworthiness, and accuracy of measurement. For current meters we do not have standards beyond physical standards of length and time upon which we can claim current meter quality and have relied instead on best practice and intercomparison to judge suitability and trustworthiness for various applications. The measurement of current is more difficult than measurement of scalars such as pressure or temperature, since, to begin with, velocity of fluid is a vector but also it has variability over small scales in space and time. Inherently, flow may be divided into mean (current), oscillatory (wave), and chaotic flow (turbulence). Thus, attributes of a current sensor for measurement of global transport of heat and momentum may be different from those of one to measure surface wave spectra, which may differ again from one to measure boundary layer stress.

The relatively high cost of acoustic current meters has placed practical limits on the use of these meters in marine research projects. One approach to reducing the cost of current measurements has been the re-invention of the Tilt Current Meter (TCM). Recent developments in accelerometers, magnetometers and low-power non-volatile memory have made it possible to make small, accurate and inexpensive TCMs. Here we describe the design and calibration of the Lowell Instruments TCM and validate its performance in Vineyard Sound, Massachusetts. The performance of four TCMs was compared to an acoustic Doppler current profiler reference meter. The TCMs exhibited an R squared correlation of 0.97-0.98 as well as low slope and offset errors. Based on this demonstrated accuracy we believe the TCM would be useful for a variety of research projects especially where there is a risk of instrument loss or where increased spatial density of measurements is desired.

Fifty years ago, an incredibly creative period of work by William S. Richardson ushered in the modern era of ocean instrumentation for measuring currents. Although an ADCP uses sonar-based technology, quite different from Richardson's devices, the functional capabilities of an ADCP can be traced to his pioneering work. ADCPs measure time series of vertical profiles of water currents. This approach merged two instrumentation streams -- current metering and vertical profiling-- both of which were founded in Richardson's work. In this paper, we review connecting threads from ADCPs to Richardson's pioneering inventions. For the most part, time variability of currents has been studied by using self-recording current meters deployed on a mooring line for an extended period. Typically their data sets described the history of concurrent motions at a few depths. Conversely, the vertical structure of currents has been studied by using free-falling velocity profilers that provided, for a time limited by cruise duration, well resolved snapshots of ocean currents throughout the water column yet separated by hours. While at Woods Hole Oceanographic Institution, Bill Richardson developed a self-recording current meter and methods for deploying several of them on a deep-sea mooring line. Later, at the University of Miami, he developed a free-falling device -- dropsonde -- for measuring water volume transport. Though distinct developments, both were motivated by the same goal: measuring the Gulf Stream.

An automated Quality Assurance and Quality Control (QA/QC) procedure implemented by Woods Hole Group, Inc. (WHG) to improve the quality of ADCP data collected on a deep Real-Time Metocean Mooring (RTMM) is described. The RTMM is equipped with three TRDI ADCPs and one Nortek single-point current meter (SPCM). A full water column current profile is collected every 20 minutes and the data are sent by satellite to a shore-based computer and web server, which creates graphical displays in near-real-time and serves them over the Internet to user’s web browsers. WHG’s automated QA/QC procedure was developed based on analysis of a first batch of ADCP data collected by the RTMM and is system-specific. The analysis of the data and of data quality indicators revealed major causes that lead to the occurrence of spurious and/or noisy current data. It also suggested approaches to improving the quality of the data provided to the client in near-real-time. The analysis revealed certain limitations of the QA/QC algorithm implemented by NDBC and recommended by QARTOD. From our experience with the RTMM data, the QA/QC of ADCP data should not be limited to automated review of quality parameters measured by the ADCP on individual ensemble-averaged profiles. A better result is achieved by adjusting ADCP setup and customizing data screening thresholds for a specific deployment. The thresholds should be customized based on the analysis of the system-specific data.

Summarization: An image-based framework for river flow monitoring based on a statistical estimation technique for fluid flow estimation is presented. This approach uses subsequent gray-scale video frames along with a statistical estimation method to extract the optical flow. An average velocity estimate is computed using the velocity vectors of the main motion trend, which is extracted using classification methods. The corresponding real-world surface velocity is computed using velocity-area transformations. The use of only two subsequent video frames and the lack of tracers in the flow are the key features of this technique in order to extract an accurate estimate of the real surface velocity. We compare our real-world surface velocity estimate with traditional current meter measurements, made on the site of Pinios river, Thessaly, Greece using the Q-liner 2 Doppler device. Παρουσιάστηκε στο: International Conference on Imaging Systems and Techniques (IST)

Current measurements, the recording of which was once powered by the current itself, is now electronic nearly everywhere. Batteries provide the energy for the electronic systems when the instrument is autonomous and the power required limits the deployment duration more seriously than the data capacity of the logger. There are several strategies that can be used to extend deployment of autonomous current meters starting with low power processors, and concluding with sophisticated sampling schemes.

A hierarchy of medium (2 km) and high (0.5 km) resolution operational models cast in the Adriatic sea (NE Mediterranean Sea), relying on an updated core w.r.t. previously existing one, characterized by having a wide variety of applications ranging from civil protection to scientific ones, is presented and described. The computing core of the system sits at Hydro-Meteo-Clima Service (SIMC, Bologna), and the scientific supervision is provided by DISVA Polytechnic University of Marche and CNR-ISMAR Venice. The core of the operational system is based on the Regional Ocean Modeling System, version 3.4. The hydrodynamic variables (e.g. sea surface elevation, currents, temperature, salinity, storm surge height), and wave parameters are predicted every day for the next 72 hours. The surface forcing for the hydrodynamic (AdriaROMS 4.0) and wave (SWAN) operational models is derived from the predicted results of the operational meteorological model COSMO-I7 (7 km resolution) which forecasts atmospheric fields over the whole Italian seas. Hydrodynamic results are verified against oceanographic and wave buoys, tide gauges, bottom mounted acoustic current meter profilers, available in the coastal waters of the Adriatic Sea and oceanographic surveys. More specifically, CNR-ISMAR in the northern Adriatic Sea manages a meteo-oceanographic buoy network and the fixed ocean observatory tower “Acqua Alta”, SIMC manages a wave buoy. Aiming to obtain forecast improvements in coastal areas of northern Adriatic Sea, a newly implemented, more resolved (0.5 km) ROMS version two-way coupled with SWAN is nested in the operational AdriaROMS 4.0 covering the Adriatic Sea at 2 km horizontal resolution. Outputs of operational models drive dedicated submodels for oil-spill transport and dispersion, coastal morphodymanic, sediment transport, saline wedge, water quality.

Reduction of vortex-induced velocity-sampling noise was demonstrated in an acoustic travel-time current meter, MAVS, by oversampling and averaging bursts of 20Hz measurements every 0.5s sampling interval during tows in the Woods Hole Oceanographic Institution flume. A characteristic vortex size of 7.37cm (from frequency and tow speed) translated into narrow band spectral peaks of velocity fluctuation with frequency proportional to tow speed. A selection of burst-sampling intervals during which 20Hz measurements were averaged was tuned to the profiling speed of the moored profiler upon which the MAVS was to be mounted. Burst-sampling improved the signal to noise ratio by almost a factor of 3 with a 4-point burst every 0.5s at 30cm/s tow (profiling) speed. This closely matched the dominant 4.3Hz vortex at 30cm/s tow speed.

The fundamental characteristics of the high-resolution ocean radar system with the VHF band under severe winter conditions in the open sea area were evaluated through the field observations in Wakasa Bay. As the results, over 60 percentage of the detection ratio of the horizontal currents by the radar was confirmed in the extent of 15km as to the maximum observation range of 25km. The comparison between the current data of the radar and that of the current meter in one-month observation at the close point to Monjyu Power Station showed good correlation with a correlation coefficient over 0.7 and the standard error of 5 to 10cm/s. It was also indicated that the currents from surface to 2.5m below the surface were mainly driven by the wind fluctuation component of the 25.3 hours with the phase of 30 minutes. The ocean surface radar could detect the horizontal current patterns in the irregular current field under the sever weather and oceanic condition, which might largely contribute to comprehend unknown ocean characteristics in an open sea.

The time evolution data of the biogeochemical and physical properties of the water column in coastal area (East/Japan Sea) located off the east coast of Korea is obtained by the coastal monitoring buoy station (ESROB, East Sea Realtime Ocean Buoy), equipped with chlorophyll a fluorometer (WQM), current meter (ADCP), PAR sensors, and Dissolved Oxygen and temperature. In April 2011, the optically-derived fluorescence sensor was installed into the buoy station within upper layer (about 1 m water depth) with highly resolved time resolution (10 min.) to examine the variability of various timespan spectrum, which has periods from diurnal to monthly variation, on the chlorophyll a fluorescence. The fluorescence time-series data showed distinct low-frequency (spring and fall blooms which is a typical characteristic in East/Japan Sea) fluctuations ranging from 0.2 μg/l to 3.8 μg/l, including abnormal summer surface bloom event in the coastal region. The high chlorophyll concentration within upper layer in summer may be attributed to surface thin low salinity water with the relatively rich nutrients flowing along the east coast of Korea through Korea Strait. Surface chlorophyll a fluorescence estimated from WQM sensor well correspond to the chlorophyll concentration derived from in situ water samples, showing a relatively high correlation coefficient (r=0.78).

Coatings to inhibit attachment of marine organisms to sensors were applied to acoustic velocity sensors and tested for seven months in near-surface waters in Woods Hole, Massachusetts and found to effectively prevent attachment of fouling organisms to substrates of ABS plastic, epoxy, urethane, and to a lesser degree to stainless steel. This treatment was effective longer than biocides generally have been in these conditions. The material in the coatings, silicone in some form, prevents the organisms from getting a tight grip and they either do not manage to settle or are washed off by natural low-velocity currents and waves in the mooring field in Eel Pond harbor.

Sensing current and logging it as an earth coordinate vector in 3-D is complex. By comparison, logging a scalar property like temperature or pressure should be simple. But that is not always so and there are issues of warm-up time, frequency response when warmed up, power consumption, voltage requirements, output format and voltage, and testing and calibrating that almost rival the complexity of making the current measurement.

Electromagnetic flow meters are widely used in multiphase flow measurements in recent years. In this paper, a simulation model is established to study the Effects of virtual current distribution in an Electromagnetic Flow Meter which exist a spherical non-conductive body in the Fluid by using ANSYS. Furthermore, the characteristics of virtual current distribution and the flow meter errors by changes the size of bubble are discussed. For application, the results provide a possible way to estimate errors of the flow meter caused by multiphase flow.

The periodicity of an under water geyser in the Taketomi submarine hot spring in Yaeyama archipelago, Japan, has been investigated. We concluded the time cycle of the geyser responds to the tide, after conducting the time series analysis of the upward velocity taken by an acoustic Doppler current meter. The time cycles in high and low tide were 66 s and 41 s, respectively. In accordance with the Bunsen's vertical tube theory, and assuming underground depth of heated domain was just 10 m below the sea bottom, that was backed up by the averaged integration of upward flux per each eruption, we also denoted the condition that temperature of heat source (Θ) of over 200 oC and the recharge water temperature (θ 0 ) of 130.57 oC could sustain the observed time cycles in high and low tide. These estimations of Θ were consistent with the previous estimations of the “deep underground water temperature” at the Taketomi Submarine Hot Spring, which ranged from 160 to 200 °C as reported by geochemists. Additionally, time variability of the relative bubble density and the relative bubble flux from the undersea geyser was investigated, utilizing the ultrasonic echo intensity and the upward velocity. A relational expression between the relative bubble density and the ultrasonic echo intensity were derived, after assuming that the (a)bubbles could be replaced by simple rigid spheres with a constant radius, (b)the bubble's radius was enough larger than the wavelength of the incident ultrasonic wave, and (c)the sound absorption by the seawater was constant. We demonstrated that at high tide, at erupting state the relative bubble density had large value, while at halting state it had quite small value. At low tide, however, the relative bubble density had almost always positive value, thus the bubbles were always present in the seawater. And the similarity between the relative bubble density and the upward velocity confirmed that the bubbles in the sea water were transported by the fluid discharged from the underwater geyser.

Personal knowledge of the author stretches from the Geodyne 850 current meter, predecessor of the VACM in 1969 to his own development of MAVS and its recent innovations. Housings, recording media, velocity sensors, and compasses have changed most noticeably. Applications of current measurements are next most striking about the developments in our field over the last 40 years. Where and how current meters are deployed have migrated from ship lowered or fixed moorings to bottom tripods, profilers on a mooring, and even to shore-based HF Radar antennas. Present developments address power to operate autonomous instrumentation, data communication in real time, and novel adaptations of current measurement techniques to non-traditional current measurement problems like horizontal profiles, turbulent mixing, and wave monitoring. New applications will be presented at this workshop, with perhaps greater emphasis than new developments in sensing.

Near-bottom (∼2 m) current velocities in the Puerto Rico Trench (∼8350 m depth) were measured at 1 Hz for 75 min by a Nortek Deep Water Aquadopp acoustic-Doppler current meter at 19.75° N, 66.40° W, via untethered free descent/ascent vehicle. The April 2008 deployment also recorded 3-axis velocity, temperature, pressure, and instrument heading, pitch, roll, and signal-strength during the 153 min free descent, and while on bottom. Signal strength was above the noise floor for the entire data set, and SNR and velocity standard deviation were within known acceptable bounds above 7000 m. Instrument heading showed a continuous anticlockwise rotation during descent. Doppler vertical velocity during descent is compared to the pressure time derivative. Integration of horizontal velocity during descent suggests a lateral displacement of less than 30 m over the 8.35 km free-fall. Measurements made at impact indicate full functionality of the instrument at depth. Maximum horizontal velocities while on-bottom varied between 1 cm/s and 5 cm/s and were directed roughly along trench axis westward.

In development of the Modular Acoustic Velocity Sensor [1, 2], MAVS, from a research instrumentation project under an NSF grant to a commercial product, I have been taught lessons by clients and colleagues that have led to changes in the product and improved the instrument made and marketed by Nobska Development, Inc. The lessons and their resulting improvements can be grouped by application and by clients who have been willing to share their successes and their difficulties. These applications range from hydrothermal vents to a coral reef, from breaking wave measurements to a very quiet lake, from near-surface wave measurements under a pier to cable connected observatory measurements, and from moored measurements to a profiler tethered to a drifting buoy.

Current measurements under ice face some challenges not present when measuring current in open water and water free of ice. There is the problem of getting the current meter through a hole in the ice, which limits the horizontal dimensions of the instrument package such as fins that might provide directional stability in open water. Then there is the issue of damage to the sensor from contact with ice in the hole, a problem that is generally less threatening in open water, so for ice deployments protection against this may be required. The small chunks of ice in the hole may interfere with the measurement, certainly a major concern with mechanical sensors, but also an issue with acoustic sensors. Finally, a mooring anchored to the moving ice surface must be tracked for recovery if data are to be only recorded internally. If the data are to be telemetered ashore there must be a data connection to the surface through the mooring line.

Measurements of velocity structure in the water column under Arctic ice from an Ice-Tethered Profiler (ITP) employed an acoustic point-measurement current meter, MAVS (Modular Acoustic Velocity Sensor) [1]. With the velocity sensor it becomes the Ice-Tethered Profiler with Velocity (ITPV). The profiler, containing a Seabird CTD, MAVS, batteries, an inductive modem, and a wire crawling engine, integrated by McLane Labs, was constrained to be deployed through a 24″ diameter hole drilled in the ice. The anchor to the ice via a buoy with a satellite transmitter fixed the top of the mooring to a drifting but GPS tracked location while the profiler descending to a depth of 800m measured velocity relative to the moving mooring and the climbing profiler. A large current-orienting alignment fin was not possible on the ITP due to the limit of the ice hole diameter yet it was known that vortex shedding by the profiler body in the current would cause the instrument to swing and the current sensor to measure horizontal velocities due to the rotation of the profiler around the center of gyration of the package. To remove this platform motion from the current measurement, an inertial sensor, Analog Devices ADIS 16355 [2], was added to the MAVS current meter and three axes of angular velocity and three axes of linear acceleration were added to each data record of time, velocity, temperature, three-axis magnetic vector components and two axes of tilt. From the rate gyro value of angular velocity around the vertical axis, the platform rotation is determined and using the distance that the velocity sensor is displaced from the axis of rotation the horizontal current sensor velocity can be subtracted from the horizontal velocity measured by the sensor. This ITP was deployed in October, 2009 and data from the first profile indicates expected and unexpected performance.

The Texas Automated Buoy System (TABS) began in 1994 when the Texas General Land Office (GLO) funded the Geochemical and Environmental Research Group (GERG) at Texas A&M University to design and purchase five telemetering current meter buoys. Instrumented buoys continuously measure current velocity about six feet below the surface and transmit the data to shore on a regular schedule via satellite telephone. The system has eight buoys funded by the TGLO operating along the Texas Coast — one near Sabine Pass, two off Galveston, one midway between Freeport and Corpus Christi, one off Corpus Christi, and two off Brownsville. The eighth buoy, a three meter discus buoy, was installed off Port Aransas in the summer of 2005 and removed in 2008. Two additional buoys located near the Flower Garden Banks National Marine Sanctuary are funded separately by an oil industry consortium but are operated as part of the TABS program. Four different types of TABS buoys are currently used by the program. All the buoys can accommodate single point current sensors. The 2.25 and 3m and TABS Π buoys can accommodate acoustic current profiling instruments and meteorological packages which include air temperature and humidity, barometric pressure, as well as wind speed and direction. The larger two buoys have both mechanical and acoustic anemometers as well as accelerometers for measuring waves. The TABS I buoys can be deployed in 10–20m water depth. The TABS II buoys are suitable for deployment in 15m to 45m water depth. The two larger buoys have been deployed in up to 110m water depth. Computers at Texas A&M University automatically collect data from the buoys every two hours via the satellite data modems and make the observations available to GLO and the general public via the Internet. TABS data are made available to NOAA NDBC via ftp to permit the data to be used by the National Weather Service. TABS sites B, J, K N and V have been given NDBC designators 42043, 42044, 42045, 42046 and 42047 respectively. In 1998 a modeling component was added to the TABS program with the development and implementation of POM adapted to perform simulations on the Texas shelf. In 2002 the modeling was extended with the implementation of ROMS. Both models are run on a regular basis and output to a web page. Wind data from National Center for Environmental Prediction (NCEP) Eta-12 wind fields are used to drive the model in nowcast and forecast modes. Hurricanes have affected the buoy system resulting in the loss of several buoys at the deeper offshore locations. The TABS 2.25m buoy was developed in an effort to deploy a buoy that could survive hurricanes. In September, 2008, the eye of Hurricane Ike passed directly over Buoy V located near the Flower Garden Banks. The mechanical anemometer was damaged but the acoustic wind sensor gave a complete record of the storms passage. Wave and atmospheric pressure data were also recorded. Perhaps most interesting is the decrease of measured waves in the eye of the storm.

Usability of the temperature output, primarily meant for temperature-compensation of the pressure output of Honeywell silicon piezoresistive precision pressure transducer (PPTR) for sea-level measurements, is presented. Laboratory calibration in the range 2-50degC against a platinum resistance thermometer showed linear response (typical example: y = 1.02X - 0.40 with R = 1). It was found that beyond 15degC, linearity and accuracy are better than 2% and plusmn1.5% respectively of the sensor's temperature output. However, the sensor's performance degrades below 15degC. Field inter-comparison measurements from an offshore platform over a period of 36 days (3456 samples) between the temperature outputs of the PPTR and those of Aanderraa current meter's Fenwall GB 32JM19 thermistor probe and NIO water level recorder's YSI thermistor probes were encouraging. However, while the Fenwall GB 32JM19 thermistor probe and the YSI thermistor probes detects changes in temperature with fine resolution, the PPTR's observed temperature resolution is O.1degC only. As precautionary measures are undertaken as a technical requirement to prevent corrosion and bio-fouling effects at the water inlet of the sensor, the PPTR could be a useful tool for acquisition of long-term temperature measurements with a resolution of O.1degC, for limited applications at least, from tropical regions where the temperature is in a range in which the sensor has a linear response.

An exhaustive current meter study was conducted last fall (2007) in the St. Lawrence Estuary in the vicinity of Gros-Cacouna, near Ile Rouge and Ile aux Lievres. Five Acoustic Doppler Current Profilers (ADCP) were deployed to monitor current speed (Cs), current direction (Cd), and wave parameters (significant wave height (Hs) and direction of propagation) over a period of twenty (20) days. Four 600 kHz Sentinel Workhorse were deployed in depths ranging from 25 to 45 m, while one 1200 kHz was deployed in the coastal area in a 15 m depth. The survey period was conducted during both neap and spring tide events. The data was analyzed for near bed, mid-depth, and surface currents at each survey sites according to direction of propagation. In general, the current direction pattern observed at all measurements sites showed that currents were mainly oriented towards North North-East and South South-West. These correspond to the tidal current directions known for this part of the estuary which are parallel to the shoreline. Important differences were observed between ebb and flood tides current speeds. The results show that currents velocity may be described using the following vertical distribution with (1) near surface currents (less than 10 m) with current speeds Cs 20 m where Cs les 1.0 m/s. Significant wave heights measured during the survey period vary between 0.1 and 1.5 m. The highest waves measured (> 1 m) originate from the western direction. The comparison between current measurements and multibeam sounding surveys collected - registered in the same area earlier in fall shows that important hydraulic dunes can be generated, suggesting suspended bed load as a significant sediment transport pattern in some parts of the Estuary.

A solution to measuring near-surface currents via a single-cell acoustic Doppler current meter with horizontally oriented acoustic beams positioned very close to the sea surface is presented. The current meter was deployed on a surface buoy on the 25 m isobath of the west Florida continental shelf. Near-surface velocity observations from the current meter (1.1 m depth) are compared to estimates from a surface mounted acoustic Doppler velocimeter (0.8 m depth) and the first several cells of a downward looking acoustic Doppler current profiler (4.0 m to 13.0 m depth). Rotary auto spectra and cross spectra analyses are used to examine the velocity gain and veering angle at different frequencies as a function of water depth. Results indicate that velocity measurements at 1.1 m were 7% higher in the M2 tidal band and 18% higher in the synoptic band than measurements at 7.0 m. There was negligible near-surface velocity rotation in both the tidal band and the synoptic band compared with measurements at 7.0 m.

We introduce an enterprise software suite to automate the processing of large-scale, large-volume current meter data for dissemination to the nation's maritime community. Currents measurement interface for the study of tides (C-MIST) is a web-based end-to-end state-of-the-art data management system to ingest, quality control, analyze, and disseminate water velocity and related data from coastal and estuarine collections. Using real-world case studies from Southeast Alaska and Galveston Bay we demonstrate how the various modules of the system allow oceanographers to apply their expertise in analyzing complex data to research natural phenomena.

NOAA's National Ocean Service's Center for Operational Oceanographic Products and Services (CO-OPS) is responsible for ensuring safe maritime navigation and supporting efficient water-borne commerce. CO-OPS oceanographic and environmental data sets also benefit the National Weather Service, coastal zone managers, and the engineering and surveying communities. In 2006, a new pilot project was introduced and implemented in the Great Lakes to measure currents in real time, horizontally across the Cuyahoga River in Cleveland, and the Maumee River in Toledo, Ohio. This project provides CO-OPS with a variety of new opportunities to expand the National Current Observation Program (NCOP) to the freshwater environment; to enhance partnerships with the Great Lakes shipping community, City of Cleveland, private industry, and federal agencies; and to test a new platform design for a horizontal acoustic Doppler current profiler developed by the U.S. Army Corps of Engineers, Detroit District. The pilots of the Lake Carriers and Lakes Pilots Associations requested assistance with navigating the Cuyahoga and Maumee Rivers where winds affect their transit through narrow bridge spans and around sharp bends. The real-time current data provides the pilots with advanced knowledge of the conditions to be expected while in transit, and thus affording them the opportunity to load the vessel accordingly before committing to the river. The pilots identified the narrowest channel of the Cuyahoga River at the Center Street swing bridge in Cleveland, Ohio as a place where real time current measurements would provide them with a worst-case scenario of current speed prior to entering the river. Another area identified by the pilots occurs as vessels inbound from Lake Erie must transit through a narrow span of a railroad swing bridge on the Maumee River as they approach the Archer Daniels Midland (ADM) pier to offload their grain. Access to the latest six minute record of current speed and direction at ADM represents conditions just beyond the bridge spans and this allows the pilot to plan an approach through this area. The real time data (every 6 minutes) can be accessed by the public through the web on the Great Lakes Online web page (http://glakesonline.nos.noaa.gov/moncurrent.html). The data are also available via NOAA's Interactive Voice Response System at 301-713-9596. Data collection of current speed and direction started in July 2006 and continues to the present at both sites. A persistent pattern has been noted at the Cuyahoga River site where a seiche oscillates approximately every 1.5 hours unless sustained winds compromise the current flow. Flow is either inbound or outbound (towards the lake) at approximately 0.8 knots. There isn't a real-time water level station upstream of the Center Street swing bridge on the Cuyahoga River so an examination of the variation in volume flow from the downstream NOS water level station located in Lake Erie cannot be simultaneously compared to the current data. A significant feature of the acoustic signal attenuation was noted at the ADM pier last winter when water temperatures approached 32 degrees Fahrenheit. Normal maximum profiling ranges diminished as the temperature dropped and approached freezing. In addition, side lobe interference also increased with the drop in temperature. Other seasonal changes in speed, temperature, and spikes in the data due to wind events are observed as well. This pilot project may include a third horizontal current meter site at the head of the St. Clair River in the vicinity of the Blue Water Bridge in Port Huron, Michigan in late 2007. Since this project is termed a pilot project, the addition of other current meter sites is dependent on follow-on funding from the US Congress or other sources.

Monitoring suspended material plumes during dredging projects or undersea construction operations is often a fundamental requirement of state and federal Section 401/404 Water Quality Certificate regulations to protect water quality and minimize potential environmental impacts. Traditional monitoring techniques typically employ in-situ turbidity monitoring and collection of water quality samples at pre-defined locations (some distance down current of the activity) and at specified times. However, sediment plumes can have complex spatial and temporal structures, specifically small length scales (order ~10's of meters) and temporal scales (order -minutes). Applying traditional sampling techniques under these conditions can result in the underestimation of suspended sediment concentrations and the collection of water quality samples that are not representative of project related impacts. Recent environmental monitoring surveys used an acoustic Doppler current profiler (ADCP) to overcome the uncertainties associated with open-water plume tracking. As a current meter, the ADCP provides real-time current data to aid in predicting the path and arrival time of a plume at a given permit compliance distance downstream. Acoustic backscatter, or the signal strength received by the transducer, provides an indicator of suspended material concentrations in the water column, allowing the ADCP to provide continuous full water depth profiles of relative suspended sediment concentrations beneath the survey vessel. This backscatter display is an essential tool to provide a high-resolution visualization of the spatial and temporal variability of the suspended material plume. As a result, the ADCP allows for improved, or "targeted", sampling and in-situ data collection from a location and depth that accurately represents water quality conditions during a given project activity.

Darvel Bay, located on the east coast of Sabah and facing the Sulawesi Sea, is the largest semi-enclosed bay in the east coast of North Borneo. In Sulawesi Sea, strong surface winds and corresponding ocean response occur during the southwest and northeast monsoon periods. The area consists of many islands and complex bathymetry contributing to its unique marine environment, which is considered as one of the most biologically diverse marine environment in the world. Water circulation and mixing play an important role on distribution of marine ecosystem components and the survival rate of marine organisms. This paper covers a study on water current velocities and water circulation patterns in Darvel Bay, under different tidal conditions and monsoonal variations, through field investigations and model calculations. Field measurements were conducted using two holey sock drogues tracking and Aquadrop Profiler current meter at the tip of Sakar Island. Hydrodynamic model calculations were conducted using MIKE 21 HD Model. The computational results were calibrated and verified using field measurement data. Based on the hydrodynamic simulations data, time series of current velocity at three location points were randomly selected around the bay to compare changes in current velocity during ebb and flood tides. Findings of this study can be used for different aquaculture activities, coastal developments and integrated coastal zone management planning in the study area.

The AquaPodTM system, developed by Ocean Farm Technologies Inc., is a submersible, spherical net pen. This cage was deployed at the University of New Hampshire's (UNH) Open Ocean Aquaculture (OOA) site for seven months for testing purposes. The cage was towed from Portsmouth Harbor to the UNH OOA site, located 15 km offshore in the Gulf of Maine, in September 2005. Water velocity and tow line tension measurements were recorded with the cage fully submerged. These values were used to determine the flow blockage caused by the cage framework and net at various speeds. Results of this tow test are being used to enhance the numerical modeling capabilities of aquaculture cage systems. The test set-up consisted of Marsh-McBirney EM and Nortek Aquadopp current meters and a Sensing Systems 53 kN load cell. The Marsh-McBirney was secured to the side of the tow vessel to measure the relative water velocity of the cage. The load cell, used to measure the towline tension, was also placed on the tow vessel. These instruments were used to record and view the water velocity and drag loads in real-time for towing purposes. The cage's interior water velocity was recorded by an Aquadopp current meter placed in the center of the cage to determine the current reduction. The cage system was brought to 5 velocity levels (constant vessel engine RPM) over 15 minutes. Each velocity level was held for approximately 2-3 minutes. The load cell measured loads from approximately 6.1 kN (1370 Ibf) at 1.08 knots to 32.2 kN (7250 Ibf) at 2.04 knots. A significant current reduction within the cage was also measured.

An extensive field study was conducted to investigate the current velocities and mooring system tensions in a 20-unit net pen fish farm located in Eastport Maine, USA, near the Bay of Fundy where extreme tides create strong currents loading fish farm components. To understand the flow characteristics at the site, currents meters were deployed at external and internal farm locations during three distinct operational conditions: (1) clean nets for smolts, (2) clean nets for standard grow out and (3) nets for standard grow out at the end of the stocking schedule, when the gear is fouled with biological material. Also, several load cells were deployed at the same time on important anchor leg and net pen attachment components to measure system loads. The current meter data sets provided evidence of velocity flow reduction through the farm by examining the current meter statistics and tidal harmonic constituents. Tidal analysis also showed substantial tidal harmonics or shallow water tides. The load cells measured maximum loads of 104 kN for anchor leg and 11 kN for net pen lines. The results are significant because few extensive fish farm engineering data sets exist, especially for different combinations of nets and levels of biological fouling. These results are being used in complementary studies to quantify flow reduction, to validate Morison equation type numerical models and as a baseline for specifying offshore fish farm gear.