Hideaki Noda

A STUDY ON MASS TRANSPORT IN BOUNDARY LAYERS IN STANDING WAVES

The distribution of bed-load sand transport normal to the beach has been measured m a series of field experiments conducted in the surf zone at Fernandma Beach, Florida. Simultaneous measurements were made of the waves and water particle motion at various locations in the surf zone. The energy flux of the waves was resolved Into Its longshore component from the measured directional and energy spectra. It Is found that the bed-load transport is related to the depth of water and longshore energy flux. Insight into the mechanics of sediment transport is obtained by comparing the wave and water particle motion energy spectra, which give a direct measure of the kinetic and potential energy, at various locations in the surf zone. INTRODUCTION A meaningful field investigation of the sand transport processes m the surf zone requires the synoptic measurement of a number of hydrodynamic and sediment variables. Fairly complete and extensive data are required to evaluate the validity of various proposed sand transport relationships and the formulations of new relationships where necessary. This paper describes field experiments conducted m the surf zone at Fernandma Beach, located on the northeastern coast of Florida. The emphasis of this study was to obtain information concerning the distribution of bedload transport perpendicular to shore and the physical processes causing such movement. Sediment transport m the surf zone can be considered as being caused by a combination of shear stresses due to wave and current action. An attempt to correlate sediment transport with physical parameters then must include good wave and current measurements. The experiments were conducted from October, 1966 to May, 1967, a period that encompasses the more intense wave activity along this coast. The beach and nearshore bottom profile is typically a one or two bar system with a gentle slope of two to three per cent. The sand has a mean grain size of approximately 0.2 millimeters. The mean tidal range is 1.7 meters.A summary is given of the results of training sixteen rivers in an endeavour to increase bar depths for navigation. The bars are of simple crescent formation fed by littoral drift. Whilst the training works have improved conditions for navigation they have not resulted in any appreciable increase in bar depths. Despite the complex mechanisms involved in bar formation a consistent simple correlation is found to exist between channel and bar depths. This correlation seems to apply to all rivers and inlets with simple bar systems and extends over a range from a bar depth of two feet to 60 feet. The correlation holds for rivers elsewhere and-- with varying climates of exposure.

MODEL STUDY ON THE FILLING-UP OF A FISHERY HARBOR BX DRIFTING SAND

INTRODUCTION For the design of a coastal structure, the height of its crown must be determined rationally and economically, taking into consideration the water level of the sea and its occurence probability. The water level in the sea is mainly referred to the astronomical tide, the meteorological effect and the short period wave. If component height according to these elements are given as; 3c, ; the tidal level, xr ; the level rise caused by meteorological origin, and x, ; the half height of wave, the level of the wave crest X at a certain tidal condition is shown by following equation under several assumption: I a i + X, + X, (1)

Developments of Technology using Ruble Mound Breakwaters for Eelgrass (Zostera marina) Bed

Nakaumi lake is shallow with extensive intertidal sand and mud flats. The eelgrass (Zoesta marina) zone in the lake may function as an important refugee for many resident and transient species, especially where other structural habitats are poor. In this paper, a new method for eelgrass bed creation is introduced and discussed Field observations have been carried out and suitability conditions of eelgrass are evaluated by field data.

Numerical Model of Dynamic Response of Flexible Floating Pier for Marina due to ocean waves

This study is concerned with the development of numerical model for the dynamic response of flexible floating pier due to ocean waves. The numerical model was induced by improving a numerical method for rigid floating structure. The motions and the tension forces of mooring lines of the pier were calculated from the method. The results of numerical simulation were compared with those of laboratory tests. It was found that the flexibility of the joints is a dominating parameter for the vertical movements the floating pier.

Study on Behavior of Fish School Around Aggregation Devices

The behavior of the fish school around the aggregation devices is evaluated numerically and experimentally. Numerical model of the fish behavior is based on the Sannomiyas model and is applied to the behavior of the Goldfish. In the tank tests the movement of the fish near of the artificial aggregation devices was analyzed by video system. Results of numerical simulation are compared with experimental results. Finally the attraction and repulsion parameters of the devices found to be a very important in estimating the the fish behavior.

Experimental study on a flexible floating pier consisted of small pontoon units for marina

This study is concerned with the development of a new floating pier for marina. This flexible floating piers consists of many small pontoon units and is moored by chains. The dynamic behavior of the floating piers due to waves is investigated through laboratory tests. The motions and the tension forces of mooring lines of the piers were compared with those of a rigid type floating piers under various wave conditions. The results show that the flexibility of the joints is a dominating parameter for the movement the floating piers for the marina

Wave Forces on the Submerged Structures for the Fish Farm

This paper deals with the determination of hydrodynamic coefficients of submerged structures which are installed in the sea to aggregate and proliferate the aquatic resources. The concept of the evaluation is to measure the non-steady oscillation of a submerged circular cylinder which is hung by a coupling rod such as a rigid body pendulum. The coefficients are determined by analysing the damping oscillation of the cylinder in still water, and the results are compared with those obtained from wave tank and oscillatory flume tests. Several methods presented herein are found easier and preciser rather than conventional methods and may be effectively employed in providing appropriate informations on the non-steady motion of the submerged and moored structures.