scholarly journals ANOTHER APPROACH TO LONGSHORE CURRENT EVALUATION

1986 ◽  
Vol 1 (20) ◽  
pp. 100
Author(s):  
M.A. Losada ◽  
A. Sanchez-Archilla ◽  
C. Vidal
Keyword(s):  
Simple Model ◽  
Predictive Model ◽  
General Expression ◽  
Current Velocity ◽  
Laboratory Data ◽  
Reynolds Stresses ◽  
Longshore Current ◽  
Current Generation ◽  
Oblique Wave ◽  
Wave Incidence

A simple model to predict the longshore current velocity at the breaker line on a beach with oblique wave incidence, is presented. The model balances driving and resistance terms (gradients of radiation and turbulent Reynolds stresses and bottom friction) to get a general expression for the velocity. This equation shows explicitely the influence of Iribarren's parameter on longshore current generation. It has been tested with field and laboratory data, obtaining a reasonable fit to measured values. The resulting (predictive) model is expected to be valid for any type of breakers though the calibration has been mainly done for spilling and plunging types, due to the scarcity of results for other breakers.

scholarly journals UNIFORM LONGSHORE CURRENT MEASUREMENTS AND CALCULATIONS

1984 ◽  
Vol 1 (19) ◽  
pp. 147 ◽  
Author(s):  
P.J. Visser
Keyword(s):  
Mathematical Model ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Friction Model ◽  
Longshore Current ◽  
Current Generation ◽  
Longshore Currents ◽  
The Mathematical Model ◽  
Lateral Friction ◽  
Good Agreement

A description is given of laboratory experiments on uniform longshore currents and the comparison of the data with longshore current profiles predicted by a mathematical model. For the mathematical model it is assumed that longshore current generation takes place between the plunge line and the shoreline (instead of shoreward of the breaker line) and Battjes' (2,3) lateral friction model is applied. Good agreement between theory and laboratory data is achieved with realistic values of the bottom roughness.

scholarly journals Intergenerational Bubbles of Beliefs for Sustainability

2020 ◽  
Vol 12 (24) ◽  
pp. 10652
Author(s):  
Keiichiro Kobayashi ◽  
Asako Chiba
Keyword(s):  
Simple Model ◽  
Political Ideology ◽  
Belief System ◽  
Future Generations ◽  
Current Generation ◽  
Dynamic Economy ◽  
Religious Doctrine

We constructed a simple model of a dynamic economy in which the current generation chooses to excessively consume, thereby rendering society unsustainable. In such an economy, we assumed that a notional bubbly asset emerges, and its value grows if the current generation conserves adequate resources for future generations. Provided that the bubbly asset is considered valuable, the current generation chooses to conserve resources, rendering the economy sustainable. The condition for sustainability is that the value of this asset grows intergenerationally and indefinitely. The asset represents a belief system, such as a religious doctrine or a political ideology. Results imply that, to restore sustainability, a new intergenerational belief system must be identified, and its value grows indefinitely.

A Towing Test of a Floating Type VAMT With Cycloidal Pitch-Controlled Blades

2018 ◽  
Author(s):  
Tomoki Ikoma ◽  
Hiroaki Eto ◽  
Koichi Masuda ◽  
Atsuhiro Oguchi
Keyword(s):  
Control System ◽  
Current Velocity ◽  
Tidal Current ◽  
Vertical Axis ◽  
Floating Structure ◽  
Current Generation ◽  
Variable Pitch ◽  
Pitch Control ◽  
Tidal Current Velocity ◽  
Vertical Axis Turbine

Sea areas around the Japanese Islands which is feasible for tidal current generation are not a lot because sea sites where tidal current velocity is above 2.0 m/s are a few. We can find such sea sites at a west side of the Kyushu Island especially. However, we would earn electrical energy to be generated if it is able to generate electricity long time using around 1.0 m/s in current velocity. A vertical axis turbine should be better than horizontal axis types because VATs can take relatively higher torque. It is very useful that we can set and control a marine turbine to be higher performance in various current velocity. The present study introduce variable pitch-control system to a vertical axis turbine for tidal current generation. The pitch-control system adapts a cycloidal mechanism so that to vary pitch angle of turbine blades is conducted mechanically. The study developed a vertical axis marine turbine with cycloidal pitch-controlled three blades which was based on previous studies and experimental data. The diameter of the turbine is 1.0 m, length of a blade is 1.3 m. The turbine was set on a floating structure in order to carry out towing tests at a sea. We obtained several kinds of data from the towing tests, which were turbine torque, the number of rotation of the turbine, output power from an electrical generator and acceleration of the floating structure. As a result, the turbine made 50 W power from the generator. Although the PTO was not so large, the pitch-control was effective very much. Some issues were found at the same time. We need to consider and develop more useful gears, assemble methods to be feasible of variable pitch system.

Numerical, Experimental and Full-Scaled Investigation on the Current Generation System of the New Deepwater Offshore Basin

2010 ◽  
Author(s):  
Tiebing Shan ◽  
Haining Lu ◽  
Jianmin Yang ◽  
Runpei Li
Keyword(s):  
Numerical Simulation ◽  
Simulation Model ◽  
Model Test ◽  
Current Velocity ◽  
Model Tests ◽  
Constant Current ◽  
Generation System ◽  
Current Generation ◽  
The Real ◽  
Current Flows

The new deepwater offshore basin was completed in 2008 at Shanghai Jiao Tong University. The current generation system is considered to be one of the most important and challenging equipments in the basin. A lot of work has been conducted to investigate the characteristics of current generation system in the new deepwater offshore basin. Main particulars and equipments of the new basin are described in detail. Some ocean deepwater tests conducted in this new basin are also introduced. Numerical simulation, model test and full-scaled measurements in the real basin were conducted to investigate the hydraulic performances of deepwater current generation system in detail. It can be concluded that the current generation system has satisfactory performances by different methods. Uniform and constant current flows with different current velocities can be generated in this new basin. Several typical current velocity profiles can also be modeled in measuring area of the basin. It indicates that the hydraulic performances of the current generation system can satisfy requirement of offshore model tests in deepwater.

scholarly journals An Analytical Study on Wave-Current-Mud Interaction

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2899
Author(s):  
S. Shamsnia ◽  
Denys Dutykh
Keyword(s):  
Mass Transport ◽  
Current Velocity ◽  
Analytical Study ◽  
Laboratory Data ◽  
Second Order ◽  
Mean Velocity ◽  
First Order ◽  
Dissipation Rates ◽  
Proposed Model ◽  
Interaction Problem

This study aims at providing analytical investigations to the first and second-order on the wave–current–mud interaction problem by applying a perturbation method. Direct formulations of the wave–current–mud interaction could not be found in the literature. Explicit formulations for the particle velocity, dissipation rates, and phase shift in the first order and the mass transport in the second-order have been obtained. The findings of the current study confirmed that by an increase in the current velocity (e.g., moving from negative to positive values of current velocity), the dissipation rates and mud (instantaneous and mean) velocity decrease. The proposed assumption of a thin mud layer (boundary layer assumption) matches with the laboratory data in the mud viscosity of the orders of (0.01 N/m2) in both wave dissipation and mud mass transport leading to small ranges of discrepancies. The results from the newly proposed model were compared with the measurements and the results of an existing model in the literature. The proposed model showed better agreements in simulating the mud (instantaneous and mean) velocity compared to the existing one.

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