Rule-of-Thumb Formulas for Extending the Versatility of Tidal Current Tables

2000 ◽  
Vol 34 (2) ◽  
pp. 18-21
Author(s):  
Ben J. Korgen
Keyword(s):  
Tidal Current ◽  
Critical Value ◽  
Tidal Currents ◽  
Current Speed ◽  
Time Interval ◽  
Local Conditions ◽  
Near Surface ◽  
Rule Of Thumb ◽  
Safety Margins ◽  
Scientific Results

Four rule-of-thumb formulas have been derived for use in conjunction with existing tidal current tables. For near-surface tidal currents, these formulas yield 1) the percent of time current speed is above a critical value, 2) the percent of time current speed is below a critical value, 3) the time interval when current speed is above a critical value, and 4) the time interval when current speed is below a critical value. The formulas presented require as inputs the near-surface tidal current speed predictions found in standard tidal current tables. Intended for making rough approximations, these formulas may be useful in planning operations for which information on near-surface tidal currents is important. They are not scientific results or predictive models on which anyone’s life should depend. They should be used only with generous safety margins and if possible, with in situ current measurements, since local conditions may vary considerably.

Electrical Power Generation by Tidal Flow Acceleration

2007 ◽  
Author(s):  
Dominique Roddier ◽  
Christian Cermelli ◽  
Alexia Aubault
Keyword(s):  
Power Generation ◽  
Tidal Current ◽  
Electrical Power ◽  
Tidal Flow ◽  
Flow Speed ◽  
Tidal Currents ◽  
Current Speed ◽  
Flow Acceleration ◽  
Renewable Power ◽  
Accelerating Structure

Hydropower is a significant contributor to the renewable power generation sector, but the energy in tidal currents is not commonly used to generate electricity. This is due to the relatively slow speed of tidal currents which does not allow for the economic development of underwater turbines in tidal regions. This paper investigates whether it is possible to increase locally the current speed in regions where the tidal current is normally not strong enough to generate significant power. The device proposed to increase current speed is composed of an arrangement of vertical walls made of poles supporting a thin membrane with suitable profile, referred to as Tidal Current Accelerating Structure or TCAS. Current turbines are to be placed in areas of accelerated flow to convert the current energy into electricity. In this paper, results of model tests that were performed to quantify the ability to increase current speed are discussed. It was found that the increase in flow velocity was not as significant as expected, probably due to interactions between the turbines and the current accelerating devices. Recall potential theory’s flow speed around a disk yields a velocity factor increase of 2 at 90 degrees from the stagnation point.

scholarly journals ESTIMATION OF ELECTRICITY GENERATED FROM TIDAL ENERGY IN BEDONO VILLAGE OF DEMAK REGENCY

2020 ◽  
Vol 4 (9) ◽  
pp. 13-17
Author(s):  
Agus Margiantono ◽  
Titik Nurhayati ◽  
Wahib Hasbullah
Keyword(s):  
Electric Power ◽  
Current Velocity ◽  
Tidal Current ◽  
Tidal Energy ◽  
Tidal Currents ◽  
Active Power ◽  
Tidal Current Velocity ◽  
The Village

In some places in the village of Bedono Demak Regency there is a location with high tidal current velocity, the coordinates of the Location is 6 ° 55'29.0 "S 110 ° 29'11.4" E. In this study estimated the amount of electric power that can be generated from tidal currents in the village Bedono. Estimates are made by modeling the location and the Darrieus turbine using the CFD (Computating Fluid Dinamyc) Software. From the research that has been done to get the results of electric power that can be produced in the village Bedono highest at 14-16 times 3469.413W and lowest 39.002W at 22-24 hours according to the CFD is the highest active power occurred at 14-16 at 3197.064W and the lowest 35.941W at 22-24 hours.

ADCP Observation and Numerical Model Prediction of Tidal Currents Near Kozu Island

2018 ◽  
Author(s):  
Tsubasa Kodaira ◽  
Takuji Waseda
Keyword(s):  
Numerical Model ◽  
Model Prediction ◽  
Vertical Profile ◽  
General Circulation ◽  
Circulation Model ◽  
Tidal Currents ◽  
Ocean Current ◽  
Near Surface ◽  
The Kuroshio ◽  
Adcp Observation

Izu island chain south of Tokyo, Japan has been considered as a prospective area for ocean renewable energy development because of relatively strong tidal currents, and the Kuroshio current. An Acoustic Doppler Current Profiler (ADCP) measurement near one of the islands, Kozu island, was conducted to know ocean current variability. The ADCP, Signature500, was installed 700m away from the coast and the water depth is 32m there. The observation period is for a month from January 8th, 2017. Vertical profile of the currents was recorded every 1 m at 1 minute interval. Based on the observation, the peak tidal currents were often more than 1m/s, and the maximum total speed exceeded 2m/s. The maximum flow is probably related to the Kuroshio intrusion because temperature increased abruptly. Typical vertical profile of the current follows the logarithmic law except for the near surface area. To study the spatial distribution of the current around Kozu island, a numerical model is developed based on MIT General Circulation Model (MITgcm). The model prediction of tidal sea surface variation is in a good agreement with the observation. The model underestimated the tidal currents, but the phase is in a reasonable agreement with the ADCP observation result.

Correlation between near-surface electromagnetic soil parameters and early-time GPR signals: An experimental study

Geophysics ◽  
2007 ◽  
Vol 72 (2) ◽  
pp. A25-A28 ◽  
Author(s):  
Elena Pettinelli ◽  
Giuliano Vannaroni ◽  
Barbara Di Pasquo ◽  
Elisabetta Mattei ◽  
Andrea Di Matteo ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Early Time ◽  
Test Site ◽  
Time Domain Reflectometry ◽  
Soil Parameters ◽  
Time Interval ◽  
Near Surface ◽  
Novel Approach ◽  
Natural Test ◽  
Ground Penetrating

We explore a new approach to evaluate the effect of soil electromagnetic parameters on early-time ground-penetrating radar (GPR) signals. The analysis is performed in a time interval which contains the direct airwaves and ground waves, propagating between transmitting and receiving antennas. To perform the measurements we have selected a natural test site characterized by very strong lateral gradient of the soil electrical properties. To evaluate the effect of the subsoil permittivity and conductivity on the radar response we compare the envelope amplitude of the GPR signals received in the first [Formula: see text] within [Formula: see text]-wide windows, with the electrical properties ([Formula: see text] and [Formula: see text]) determined using time-domain reflectometry (TDR). The results show that the constitutive soil parameters strongly influence early-time signals, suggesting a novel approach for estimating the spatial variability of water content with GPR.

Analysis of seismic efficiency of the electromagnetic pulse source "Yenisei"

2020 ◽  
Author(s):  
Oxana Sadovskaya ◽  
Vladimir Sadovskii ◽  
Evgenii Efimov
Keyword(s):  
Granular Materials ◽  
Electromagnetic Pulse ◽  
Seismic Sources ◽  
Time Interval ◽  
Pulse Source ◽  
Surface Soils ◽  
Low Frequencies ◽  
Periodic Action ◽  
Near Surface ◽  
Seismic Efficiency

<p>We developed a computational technology for numerical modeling of wave fields generated by seismic sources in blocky-layered geological media, and applied it to the analysis of efficiency of the electromagnetic pulse source of new generation "Yenisei", created recently by international geotechnical company "Geotech Seismic Services". To describe wave processes, we worked out new mathematical models of the dynamics of elastic, viscoelastic and elastic-plastic media, of porous and granular materials taking into account the increase in stiffness of such materials as pores collapse, [1]. Algorithms of numerical implementation of governing equations were realized for the cluster-type supercomputers, based on the method of two-cyclic splitting with respect to spatial variables. The conducted computational experiments have demonstrated that the proposed technology allows reproducing the system of waves near the region of excitation of seismic oscillations in 3D setting with a high degree of details and accuracy, [2]. We analysed frequencies and amplitudes of waves generated in the near-surface soils, and showed that our computational results are in a good agreement with seismic parameters of a real electromagnetic pulse source. We studied seismic efficiency of the pulse source as the ratio of the energy passing through the reflecting surface in the depth of layered massif to the energy of pulse effect on the surface. Besides, the energy of surface waves, which is obviously useless for the excitation of reflected waves, was estimated. To compare the energy efficiency of pulse sources with seismic sources of periodic action (vibrators), the problem of cyclic loading through the platform was solved numerically by the same method and the same geometric scheme. The seismic efficiency of vibrator was calculated by the maximum value of the energy fluxes during large time interval. Judging by computations, the pulse seismic sources are not inferior to the sources of vibratory type by seismic efficiency in the range of low frequencies. However, it is necessary to take into account that they differ sharply by the level of expended energy, because the energy of a pulse source, needed for generation of incident wave of a given amplitude, is many times lower than the energy of a vibrator.</p><p>The reported study was supported by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project No. 18-41-242001: "Analysis of wavy seismic fields generated by the electromagnetic pulse source "Yenisei" in heterogeneous soil massifs during geological exploration in the conditions of northern regions of Eastern Siberia".</p><p>References</p><ol><li>Sadovskaya O., Sadovskii V. Mathematical Modeling in Mechanics of Granular Materials. Ser.: Advanced Structured Materials, vol. 21. Springer, Heidelberg – New York – Dordrecht – London, 2012. 390 p.</li> <li>Sadovskii V.M., Sadovskaya O.V., Efimov E.A. Analysis of seismic waves exited in near-surface soils by means of the electromagnetic pulse source "Yenisei". Materials Physics and Mechanics. 2019. V. 42, No. 5. P. 544–557.</li> </ol>

Non-Dimensional Parameters Governing the Onset of Wake-Induced Marine Riser Collision

2003 ◽  
Author(s):  
Shan Huang ◽  
Wusheng Wu
Keyword(s):  
Critical Current ◽  
Large Amplitude ◽  
Low Frequency ◽  
Critical Value ◽  
Current Speed ◽  
Loss Of Stability ◽  
Marine Riser ◽  
Dimensional Parameters ◽  
Stationary Bifurcation

Wake-induced riser oscillation can lead to riser clashing. Furthermore, the onset of the wake-induced riser oscillation, which is typified by its large amplitude and low frequency, is attributed to the loss of stability of the downstream riser in the wake once the current exceeds a critical value. The loss of stability is mathematically characterised by a stationary bifurcation. Based upon our previous work, further results are presented in the paper on the non-dimensional parameters which govern the critical current speed. These non-dimensional parameters, once computed, can then be used by riser designers to assess potential riser clashing and/or ascertain the minimum riser spacing and top tension required in order to avoid riser clashing.

Investigations Into Tidal Current Turbine System Faults and Fault Tolerant Control Strategies

2020 ◽  
Author(s):  
Xuhua Yan ◽  
Rosemary Norman ◽  
Mohammed A. Elgendy
Keyword(s):  
Tidal Current ◽  
Fault Tolerant ◽  
Control Strategies ◽  
Synchronous Generator ◽  
Fault Tolerant Control ◽  
Current Speed ◽  
Tidal Current Energy ◽  
Speed Sensor ◽  
Tidal Current Turbine ◽  
Current Turbine

Abstract In recent years, there has been a growing interest in tidal current energy as it is a potential source for green electricity generation and the most predictable form of ocean renewable energy. Due to the harsh marine environment, the Tidal Current Turbine (TCT) system has to be designed to be robust and to work reliably with high availability to minimize the need for intervention. Thus, fault tolerant control strategies are needed to enable the system to continue operating under some fault conditions, this will reduce the power generation cost and also increase the system robustness. This paper introduces some of the different fault conditions that may occur in TCT systems such as sensor faults, especially tidal current sensors. Potential solutions for these faults are then introduced. The paper then presents a standalone TCT generation system model with perturb and observe (P&O) control; this control aims to solve the tidal current speed sensor fault problem, ensuring that the system operates near the maximum power point (MPP) without the tidal current speed sensor. The control system is simulated using MATLAB/Simulink, for a TCT, utilizing a permanent synchronous generator (PMSG) and a boost converter.

scholarly journals On the Sensitivity of Typhoon Wave Simulations to Tidal Elevation and Current

2020 ◽  
Vol 8 (9) ◽  
pp. 731 ◽  
Author(s):  
Shih-Chun Hsiao ◽  
Han-Lun Wu ◽  
Wei-Bo Chen ◽  
Chih-Hsin Chang ◽  
Lee-Yaw Lin
Keyword(s):  
Wave Height ◽  
Tidal Current ◽  
Outer Region ◽  
Wave Model ◽  
Tidal Currents ◽  
Integrated System ◽  
Wave Direction ◽  
Wind Fields ◽  
Tidal Elevation ◽  
Typhoon Wave

The sensitivity of storm wave simulations to storm tides and tidal currents was investigated using a high-resolution, unstructured-grid, coupled circulation-wave model (Semi-implicit Cross-scale Hydroscience Integrated System Model Wind Wave Model version III (SCHISM-WWM-III)) driven by two typhoon events (Typhoons Soudelor and Megi) impacting the northeastern coast of Taiwan. Hourly wind fields were acquired from a fifth-generation global atmospheric reanalysis (ERA5) and were used as meteorological conditions for the circulation-wave model after direct modification (MERA5). The large typhoon-induced waves derived from SCHISM-WWM-III were significantly improved with the MERA5 winds, and the peak wave height was increased by 1.0–2.0 m. A series of numerical experiments were conducted with SCHISM-WWM-II and MERA5 to explore the responses of typhoon wave simulations to tidal elevation and current. The results demonstrate that the simulated significant wave height, mean wave period and wave direction for a wave buoy in the outer region of the typhoon are more sensitive to the tidal current but less sensitive to the tidal elevation than those for a wave buoy moored in the inner region of the typhoon. This study suggests that the inclusion of the tidal current and elevation could be more important for typhoon wave modeling in sea areas with larger tidal ranges and higher tidal currents. Additionally, the suitable modification of the typhoon winds from a global atmospheric reanalysis is necessary for the accurate simulation of storm waves over the entire region of a typhoon.

scholarly journals Evaluation of effect factors on water quality of Karun River in downstream and lake of the Gotvand-e-Olya Dam (SW Iran)

2019 ◽  
Vol 9 (7) ◽  
Author(s):  
M. Jahangiry Fard ◽  
H. Amanipoor ◽  
S. Battaleb-Looie ◽  
K. Ghanemi
Keyword(s):  
Water Quality ◽  
Saline Water ◽  
Principal Component ◽  
Time Interval ◽  
Time Sampling ◽  
Multivariate Statistical ◽  
Local Conditions ◽  
Ionic Ratios ◽  
Reverse Ion Exchange ◽  
Sw Iran

Abstract Outcrop of Gachsaran evaporative formation in the lake of Gotvand-e-Olya Dam in SW IRAN has posed a major challenge in terms of water quality. In the present study, multivariate statistical analysis, ionic ratios, and Piper diagram were utilized to investigate the effect of formation dissolution on water quality. Sampling was performed two times with a time interval of 6 months. The result showed that the types of downstream samples are Cl–Na and Cl–Ca, which are affected by the dissolution of Gachsaran Formation and reverse ion exchange. Due to the transmission of the saline water to the depth and layering of reservoir, the water types in the upper levels of dam’s lake are (SO4–Ca and HCO3–Ca) and (Cl–Ca and SO4–Ca) upon the first and second sampling, respectively. In both times, the clustering of the EC, TDS, Na, and Cl parameters demonstrates the effect of halite dissolution on water quality in downstream and lake of the dam. At the first sampling, the SO4 and HCO3 parameters are in one cluster that shows increasing calcareous formation dissolution. At the second time, the grouping of the Ca and SO4 parameters shows the effect of gypsum and anhydrite dissolution on water quality. In both sampling times, the stations are grouped based on distance to the dam such that upstream stations are in one cluster. Results of principal component analysis show that data of the first-time sampling are summarized into two factors that show the effect of the formation dissolution and rainfall effect on water quality, respectively. At the second-time sampling, studied parameters are summarized in one factor. Local conditions of the studied area indicate the dominant effect of formation dissolution on water quality. The results of ionic ratios confirm the effect of geological formation on water quality in the lake and downstream of the dam. Due to the water layering, in terms of salinity in the dam’s lake, the rate and discharge of water outflow of the dam also affect the water quality in downstream.

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