Wave Height Sensor Research Articles

Sensitivity characteristics of a wave height sensor based on a MEMS piezoresistive cantilever and waterproof film

Abstract This paper presents the frequency characteristics of a barometric pressure-sensing wave height sensor employing a microelectromechanical system (MEMS) piezoresistive cantilever and a micromesh waterproof film. The proposed sensor exhibited mechanical bandpass filter characteristics owing to air leakage around the cantilever and film. Consequently, high robustness can be achieved if the frequency is designed to match the wave range. We theoretically and experimentally verified that the frequency response is influenced by the film's chamber volume and permeability constant. We demonstrated that the proposed frequency-response model helps design a waterproof wave height sensor using a cantilever-type differential pressure sensor.

Uncertainty Analysis Study on Seakeeping Tests of Benchmark Model

Experimental uncertainty and measurement, particularly in engineering, have been increasingly emphasized over the last 20 years. Uncertainty analysis of ship model testing in seakeeping experiments based on International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), report with recommendations published by ITTC (2008). In this paper, the uncertainties for free-running tests were performed for a model scale 1:62 as a benchmark model test at the Indonesian Hydrodynamic Laboratory (IHL). The benchmark model is representative of a full scale of 186 meters. The model has full appendages as well as a rudder and propellers to allow for free-running tests, natural roll period, free roll decay, and swing tests. Factors of basic uncertainty (type A and type B) are estimated using model tests. The standard deviation of the mean value of a repeated measurement is uncertainty type A. However, Type B uncertainty is estimated from manufacturing specifications. The uncertainty components resulting from both types are quantified by standard deviations. The uncertainty value of Type B is approximated by a corresponding variance. This study helps to understand the underlying uncertainty associated with this research, which resulted in a total geometry uncertainty value (Lpp, B, T, H, , and kyy) of 0.17598% and the total uncertainty value of the instrument calibration results (wave height sensor and qualysis motion tracking) is 0.01161%. The results of this study are expected to minimize the impact of sources of uncertainty and allow the potential for underlying uncertainty to be corrected for the next seaworthiness test.

Prediction of Air Pressure Change Inside the Chamber of an Oscillating Water Column–Wave Energy Converter Using Machine-Learning in Big Data Platform

Wave power is an eco-friendly power generation method. Owing to the highly volatile nature of wave energy, the application of prediction techniques for power generation, failure diagnosis, and operational efficiency plays a key role in the successful operation of wave power plants (WPPs). To this end, we propose the following approaches: (i) deriving the correlation between highly volatile data such as wave height data and sensor data in an oscillating water column (OWC) chamber; (ii) development of an optimal training model capable of accurate prediction of the state of the wave energy converter (WEC) based on the collected sensor data. In this study, we developed a big data analysis system that can utilize the machine learning framework in KNIME (an open analysis platform), and to enable smart operation, we designed a training model using a digital twin of an OWC–WEC that is currently in operation. Using various machine learning models, the pressure of the OWC chamber was predicted, and the results obtained were tested and evaluated to confirm its validity. Furthermore, the prediction performance was comparatively analyzed, demonstrating the excellent performance of the proposed CNN-LSTM-based prediction model.

Design and test of large-range wave height sensor based on water resistance measurement and fuzzy system

Aiming at the easily damaged capacitive wave height sensor and the requirement for large-range wave height measurement in large-scale wave-making experiment, a large-range wave height sensor based on measuring water resistance is proposed. The mechanical structure, detection circuit, and the selection of main components of the sensor are described in detail. The parallelism of the two measuring electrodes is guaranteed by tensioning and rotating mechanism. In order to overcome the polarization phenomenon of water in the state of electrification, AC power supply is used as signal source. Compensation electrodes are installed to compensate for the effects of water quality and temperature changes. In addition, this paper uses the T-S fuzzy system theory to realize the fault diagnosis of the wave height sensor. Through linearity test, water quality change test, and contrast test with visual wave height measurement system, it can be seen that the sensor has high linearity and is not affected by water quality change, and the measurement results are accurate and reliable.

Observation of Surface Water Temperature and Wave Height along the Coast of Pohang using Wave Gliders

ABSTRACT Ko, S. H.; Hyeon, J. W.; Lee, S. J, and Lee, J. H., 2018. Observation of Surface Water Temperature and Wave Height at the Coast of Pohang using Wave Glider.. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1211–1215. Coconut Creek (Florida), ISSN 0749-0208. Wave Gliders were launched to observe the surface water temperature and wave height at Hwajin-ri and Josa-ri on the coast of Pohang for the 11 days from March 24th to April 3rd. Wave Gliders SV2 and SV3 were operated within a radius of 100 m at two sites at depths of about 30~40 m. Both vehicles were equipped with a weather sensor, wave height sensor, and camera. Additionally, a conductivity sensor was installed in the SV2. During the observation period, the average surface water temperature and significant wave height were 13.0°C and 0.7 m, respectively. The differences in the surface water temper...

해상기상탑 설계에 관한 연구

A meteorological(met) tower is the first structure installed during the planning stages of offshore wind farm. The purpose of this paper is to design the met tower with tripod bucket type support structure and to install the sensors. The support structure consist of a central steel shaft connected to three cylindrical steel suction buckets which is more cheaper than monopile or jacket type. And the remote wind condition sensors and marine monitoring equipment, including adcp, pressure type tide gauge, wave height sensors, and scour sensors, remote power supply are installed. The manufactured met tower constructed on sea area which is in front of Gasa island. All of functions of met tower showed normal operation conditions and the wind data got by remote data collection system successfully.

The Design of Wave Data Acquisition and Time-Domain Analysis Program

In this paper, a specific method is presented for designing program of wave data acquisition and time-domain analysis, which includes brief description of wave height sensor, the basic concepts related to wave data time-domain analysis and specific idea and method of program design. Firstly, computer receives wave data through the serial port. While MSComm control is used for serial prot programming for the most part.Secondly, the methods of the average of some big waves and cumulative rate of value are both used in time-domain analysis of wave data. According to the practical test, the program is stable, expeditious and accurate highly.

J051065 加振水槽における液面挙動解析へのEFD/CFDの活用([J05106]流体機械の研究開発におけるEFD/CFD(6))

Various fluid phenomena appear in AT(Automatic Transmission) depend on the parts and conditions. Acceleration by starting and braking a vehicle, affect the free-surface phenomena in oil pan of AT. Visualized apparatus for accelerated water vessel was established for analysis of the phenomena. EFD techniques, using high-speed camera, laser sheet visualization and wave-height sensor array, evaluate the precision criteria of CFD for free-surface phenomena. As a result, wave-height accuracy was within 10% and the time delay was within 40 msec.

単独測位方式によるＧＰＳ波浪観測システムの実証実験

Ocean wave information is indispensable for a coastal activity and service of ship to be carried out safely and economically. A low-cost wave height and direction sensor was developed by Japan Aerospace Exploration Agency and Japan Weather Association. The purpose of this study is to examine observation accuracy of wave height, period, and direction on the light buoy of Japan Coast Guard. Then, we installed a low-cost wave height and direction sensor on the light buoy and observed ocean wave in the sea. And, we compared data observed by light buoy with data observed by NOWPHAS (Nationwide Ocean Wave information network for Port and HArbourS). Our results show that observation accuracy on the light buoy is high.

Experimental investigation of slosh dynamics of liquid-filled containers

This paper is concerned with the experimental studies on the sloshing response of liquid-filled containers. A three-dimensional finite element analysis is carried out for the numerical simulation of this problem. The effects of sloshing are computed in the time domain using Newmark's time integration scheme. A simple experimental setup is designed and fabricated in-house to conduct experiments for measuring some of the basic parameters of sloshing. A sensor device is especially developed to record the free-surface wave heights. Each wave height sensor is a capacitance probe that detects the change in level of liquid (water) precisely with no time lag. The sensors are used in conjunction with a signal-processing unit in which the capacitance values are transduced to a voltage signal between 0 V and 10 V. These wave height sensors simultaneously record the slosh wave height near the periphery of the container wall from 16 predetermined locations to give the free-surface profiles of liquid at desired time steps. The experimental results are compared with those obtained from the present theoretical analysis, and good agreements are observed.

Ship-Borne Wave Height Measurements

An extensive full scale performance evaluation of the USNS 17CTORIOUS T-AGOS 19 was undertaken by the ship design community to validate the hydrodynamic performance capabilities of this Small Waterplane Area Twin Hull (SWATH) ship To assess the performance characteristics of the hull form, sensors, signal conditioning instrumentation, and data acquisition computer systems were installed on hoard. Real-time characterization of the seaway during trial operations represented a key element in the overall evaluation of the rough water performance of this SWATH ship, as would also he the ease for many other surface ships. During this full scale trial program the seaway was quantified through wave height measurements made at the how of the ship using a commercially available ship-borne wave height sensor. The major advantages of using a ship-horne wave height sensor include: measurement of seaway parameters in seas too severe to launch a buoy, reduced trial dawn-time associated with buoy launch and recovery, and an increase in collection time of seaway data available at zero speed as well as underway. A wave height buoy was also employed on several occasions primarily for comparison with the ship-horne wave height measurements. The comparisons of ship-home wave height measurements with wave buoy measurements show reasonable agreement and provide confidence in the overall accuracy of the wave height measurements. For comparison, wave spectra measured during the trials are also presented along with a theoretical Bretschneider spectrum at approximately the same significant wave height and modal period. The results indicate good agreement between the wave spectra derived from data measured using the ship-home sensor and what is expected in a theoretical spectral formulation of a well developed seaway

Imaging surface-wave analyzer for liquid surfaces

We have developed a wave-height sensor that can be used to measure surface height directly and simultaneously over a two-dimensional imaged area of an air-liquid interface, thus permitting real-time two-dimensional wave-height spectra to be obtained directly by fast Fourier transform. The absolute interface height (or surface-wave amplitude) is obtained directly from the measured volume attenuation of the transmitted light through the medium rather than by tedious reconstruction from surface slope data obtained by light refraction or reflection methods. A surface-height resolution of tens of micrometers has been achieved. For this demonstration, two-dimensional gray-scale wave-height images of cylindrical surface waves are presented with corresponding two-dimensional fast Fourier transforms. Line scans across the images indicate the ready utility of the instrument to obtain surface-height information at any location on the imaged area. Applications of this diagnostic and design issues of a two-dimensional wave-height spectrum analyzer are presented.

Bayesian Estimation of Directional Wave Spectra Based on Ship Motions

In this paper, the authors carried out model tests to estimate directional wave spectra from only a set of simultaneous records of ship motions. Based on the assumption of linearity between the waves and the ship motions, many studies which estimate the wave power spectra by using only data of ship motions have been done. However, there are few results for estimation of directional wave spectra based on only information of ship motions. The estimating calculation in this paper consists of three steps. The first step is a calculation of cross spectra of ship motions by a stochastic approach using a multidimensional auto regressive model. The second one is a theoretical calculation of frequency response functions of the ship from the waves by New Strip Method. And, the last one is an estimation of directional wave spectra by using Bayesian Model. In order to discuss the quantitative accuracy of this method, some results were compared with the ones estimated from the observing data in an array of wave height sensors. Successful agreement between measured and estimated directional wave spectra was obtained. And the power spectra which were obtained by integration of the estimated directional wave spectra also agreed quantitatively with the measured ones.

船体運動データからの方向波スペクトルの推定について-II : 水槽実験による推定精度の検討

This paper deals with the quantitative accuracy of directional wave spectra which are estimated from a set of simultaneous records of ship motions. The Extended Maximum Likelihood Method with a stochastic approach is used using a multidimensional auto regressive model. A method for correction with the use of cross spectra of ship motion is also proposed. Some results of model tests which were carried out in a wave tank with an array of wave height sensors are given. In order to examine the estimating accuracy, directional wave spectra estimated from ship motions are compared with those based on the array of wave height sensors. The direction in which a directional wave spectrum takes the maximum value can be estimated by this method. See also abstract no. 92071622.

A field study of wave reflections from an exposed dissipative beach

This paper describes a field study of wave reflections from an exposed dissipative beach, using only water-surface elevation data from five wave height sensors. Many insights were gained into beach reflections and their detection. A technique normally reserved for laboratory use was successfully applied to surf zone data to separate incident and reflected infragravity wave-energy spectra. The reflected wave energy was found to be significant for all wave periods greater than 20 seconds, and often total for wave periods greater than 30 seconds. The evidence was heavily weighted towards the observed reflected wave activity being essentially two dimensional with the influence of three-dimensional edge waves being minimal. Other findings relate to the value of wave energy spectra computed from a single surf-zone sensor, the relevance of single slope approximations of beach profiles and the relationship between incident infragravity wave-activity and the longer-period swash excursions on a beach face.

Wind stress over water waves: Field experiments on lake of Geneva

A fixed platform (Fig.3), installed 100 m from the shoreline in 3 m water depth, was instrumented with velocity, temperature and wave-height sensors. 132 data (10 minutes averages) were analysed to calculate the wind stress; from these, 99 data were used to investigate the vertical distribution of the wind stress; all data are presented with Table 1.

Aerodynamic drag: Measured at a nearshore platform on lake of Geneva

A fixed platform was constructed 100 m from the shoreline in 3 m water depth in the Lake of Geneva; it was instrumented with velocity, temperature and wave height sensors. The 145 data (10 minutes averages) were analysed to obtain the drag coefficient for wind speeds of 7 < u to < 17 m/s and for weak stratifications. The (1)Theoretical Considerations, needed for the data interpretation are presented first.

High‐frequency acoustic sea surface scatter correlated with wind and wave measurements

Backscatter and forward‐scatter measurements were made at frequencies ranging from 20 to 50 kHz (principally 21 and 40 kHz) in Lake Washington. Simultaneous measurements were made of the wind speed, stress, and direction, and of the large and small scale wave height up to frequencies of 30 Hz. The wave height sensors penetrated the water surface at the approximate center of the area of ensonification, allowing a spatially as well as temporally simultaneous comparison of scattering levels with wave height. Preliminary results show the backscatter level to be about 10 dB less than in the open ocean for a given wind speed. This result may be due to differences in near‐surface bubble size density distributions between salt and fresh water [Scott, Deep‐Sea Res. 22, 653–657 (1975)].

Wind Stress and Heat Flux over the Ocean in Gale Force Winds

Abstract An offshore stable platform has been instrumented with wind turbulence, temperature and wave height sensors. Data from this platform have been analyzed by the eddy correlation method to obtain wind stress and heat flux at wind speeds from 6 to 22 m s−1 in a deep-water wave regime, significantly extending the range of available measurements. The sea surface drag coefficient increases gradually with increasing wind speed. Sensible heat fluxes have been observed over a much wider range than previously available. Heat flux coefficients are higher in unstable than stable conditions, but are not seen to increase with increasing wind speed.

A Solid-State Digital Tide Gauge

A new type of marine water-height sensing device has been designed and built for use as a tide gauge. Primary prerequisites for the instrument were inexpensive construction, avoidance of moving parts, reliability of operation in a marine environment, and direct computer interface for automated data acquisition. The resultant instrument employs carbon electrodes fixed to a polyvinyl chloride pipe, and remote electronics to sense water level in the pipe. The electronics were designed so as to minimize current through the electrodes. The design is adaptable to different tidal ranges and resolutions, and could also be used as a wave-height sensor.