scholarly journals HORIZONTAL DIFFUSION IN A TIDAL MODEL

1974 ◽  
Vol 1 (14) ◽  
pp. 139
Author(s):  
Haruo Higuchi ◽  
Tetsuo Yanagi
Keyword(s):  
Dimensional Analysis ◽  
Tidal Current ◽  
Hydraulic Model ◽  
Residual Flow ◽  
Tidal Model ◽  
Horizontal Diffusion ◽  
Vertical Scale ◽  
Tide And Tidal Current ◽  
Sea Area ◽  
Shallow Bay

The effect of the tidal residual flow on the horizontal diffusion in a shallow tidal bay is investigated through a hydraulic model experiment, for which Mikawa Bay in central Japan was used as a prototype. A hydraulic model of about 20 x 30 m including Mikawa Bay and neighboring sea area, with a horizontal and vertical scale of 1/2000 and 1/160 respectively, was used, and a semi-diurnal tide was provided for it. Experiments nave shown that tide and tidal current are well reproduced in the model. The tidal locus does not close, that means the existence of the residual flow. The distribution of the concentration of the dye, which is discharged from the bay bottom, corresponds to the pattern of the residual flow. The diffusion coefficient in the bay obtained through one dimensional analysis is the order of 10' cm2/sec and that through two dimensional analysis is less by one order and the dispersion coefficient becomes 105 cm2/sec. It is concluded that the dispersion due to the residual flow plays more important role on the distribution of the material in the shallow bay, as Mikawa Bay, than the diffusion due to the tidal current itself.

scholarly journals TIDE AND TIDAL CURRENT IN THE BALI STRAIT, INDONESIA

2015 ◽  
Vol 36 (2) ◽  
pp. 25-36 ◽  
Author(s):  
Dessy Berlianty ◽  
Tetsuo Yanagi
Keyword(s):  
Tidal Current ◽  
Ecological Model ◽  
Current Model ◽  
Spring Tide ◽  
Residual Flow ◽  
Tidal Front ◽  
Shelf Seas ◽  
Shallow Area ◽  
Tidal Constituents ◽  
Tide And Tidal Current

Tide and tidal current model of the Bali Strait in Indonesia is produced by using a Coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas (COHERENS). With its resolutions in the horizontal (500meters) and the vertical (4layers), the model well reproduces the four major tidal constituents, namely M2, S2, K1, and O1 tides, and their currents. Furthermore the model is used to investigate the tide-induced residual flow and tidal front in the Bali Strait. As a results, the tide-induced residual flow in the Bali Strait during the spring tide on May 16th in 2010 can be attributed to the variation of the strength of two eddies. The first one is the clockwise circulation in the shallow area at the wide part of the strait, while the second one is the small clockwise circulation in the south of the narrow strait. On the other hand, as suggestion from Simpson and Hunter (1974), the tidal front is determined by the value of log(H/U3) (where is the water depth in meters and the amplitude oftidal current amplitude in ms-1). The front detected by the image of sea surface temperature distribution from the satellite corresponds with the contour log(H/U3) of 6.5.

scholarly journals ELBE TIDAL MODEL WITH MOVABLE BED

1972 ◽  
Vol 1 (13) ◽  
pp. 137 ◽  
Author(s):  
Hans Vollmers ◽  
Egon Giese
Keyword(s):  
Morphological Changes ◽  
Fixed Bed ◽  
Solid Material ◽  
Test Results ◽  
Tidal Model ◽  
Vertical Scale ◽  
Tidal Estuaries ◽  
The Elbe River ◽  
Sea Area ◽  
Movable Bed

The Bundesanstalt filr Wasserbau (BAW) was charged to investigate an estuary tidal model of the Elbe-river (North Sea). The model, fitted with a movable bed, serves for special research with regard to suitable actions for the enlargement and maintenance of the main navigable channel in the sea area. Because in tidal estuaries the interaction of fluid and solid material is extremely unknown, the investigation was undertaken to find out the arising morphological changes, only caused by tidal currents, considering structure or dredging works present or planned in prototype. The procedure seems advantageous and a better way as speculative interpretations of sediment movements, derived from flow velocities in a fixed bed model. The horizontal scale of the model is 1:800, the vertical scale 1:100. After basic considerations as similarity, hydrology, morphology, respectively, specifications of the modelling technique are given and finally some test results are discussed.

scholarly journals ADAPTABILITY OF PREDICTION METHOD OF HYDRAULIC MODEL EXPERIMENT FOR THERMAL DIFFUSION

1976 ◽  
Vol 1 (15) ◽  
pp. 175 ◽  
Author(s):  
Masanobu Kato ◽  
Akira Wang
Keyword(s):  
Heat Exchange ◽  
Nuclear Power ◽  
Water Discharge ◽  
Cooling Water ◽  
Prediction Method ◽  
Hydraulic Model ◽  
Surface Heat ◽  
Horizontal Scale ◽  
Vertical Scale ◽  
Surface Heat Exchange

In formation processes of the region of water temperature rise caused by the cooling water discharge from thermal and nuclear power stations located on the site facing the ocean, flow of discharged cooling water itself, current and turbulence existing in the sea region play an important role. Their motions are predominant in the horizontal direction in the sea region. The horizontal scale of thermal extent is, therefore, extremely larger than the vertical scale of thermal extent. Therefore, whenever the diffusion experiments of discharged warm water in the far field are conducted by hydraulic model method, the model which has a difference in the geometrical reduced rate between the horizontal and vertical directions, what is called, the distorted model must be used, so that the effects of the viscosity and the surface tension on the experimental model can be avoided. In such a model, the horizontal scale is determined by the relation between the size of the experimental water basin and the surface area of the sea region to be reproduced. But, there is no clear method of choosing the vertical scale, though there are some suggestions about it. For example, the similarity of the 4/3 power law of the diffusion coefficient gives a relation between the vertical scale and the horizontal scale of the hydraulic model. On the other hand, the similarity of the surface heat exchange coefficient gives another relation between the vertical scale and the horizontal scale of hydraulic model if the surface heat exchange coefficients of hydraulic model and prototype are not same. Therefore, it is better to give some allowance in the determination of the vertical scale of the hydraulic model within the range where the reproducibility of the diffusion phenomena can be conserved.

scholarly journals Decrease in Tide and Tidal Current in Ariake Bay

2004 ◽  
Vol 13 (4) ◽  
pp. 403-411 ◽  
Author(s):  
Takamichi Fujiwara ◽  
Yusaku Kyozuka ◽  
Takaharu Hamada
Keyword(s):  
Tidal Current ◽  
Ariake Bay ◽  
Tide And Tidal Current

scholarly journals Research on Performance Evaluation of Tidal Energy Turbine under Variable Velocity

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6313
Author(s):  
Chuhua Jiang ◽  
Xuedao Shu ◽  
Junhua Chen ◽  
Lingjie Bao ◽  
Hao Li
Keyword(s):  
Performance Evaluation ◽  
Flow Velocity ◽  
Flow Rate ◽  
Tidal Current ◽  
Evaluation System ◽  
Average Power ◽  
Tidal Energy ◽  
Time Varying ◽  
Practical Applications ◽  
Sea Area

Aiming at the performance evaluation problem of tidal energy turbines in the application of periodic time-varying flow velocity, with the goal of maximizing the efficiency of energy harvesting in practical applications, an evaluation system combining the characteristics of flow velocity changes in practical applications is proposed. After long-term monitoring of tidal current flow velocity in the applied sea area, the actual measured tidal current periodic flow velocity is divided into several flow velocity segments by using statistical segmentation, and the evaluation flow velocity of each flow velocity segment and its time proportion in the tidal current cycle are obtained. A test device with constant torque regulation is built, and capture power tests of different torque loads are carried out under each evaluation flow rate. After comparison, the maximum captured power at each evaluation flow rate is determined. We calculate the weight based on the time proportion of each evaluation flow velocity and obtain the turbine average power of the tidal cycle, thereby evaluating the overall energy capture performance of the turbine under the periodic time-varying flow velocity. Finally, the application test of the turbine in the actual sea area shows that the thin-walled airfoil turbine is more suitable for the sea area, which is the same as the pool evaluation result. The result shows that the evaluation system is reliable and effective and has significance for guiding practical engineering.

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