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The applicability of a k-e turbulence model for low-Reynolds numbers to oscillatory boundary layers is examined. Through several numerical computations, characteristics of the mean velocity and tur...

Two-dimensional laboratory experiments were performed to investigate the sediment transport due to waves on a smooth fixed sloping beach. Polystyrene particles and glass balls were used as tracers ...

In order to clarify the water particle velocity field of breaking waves on beaches, experiments were carried out for three kinds of beach slopes (1/10, 1/20 and 1/30). Neutrally buoyant particles were used as tracers to measure the velocities with a 16 mm high speed cinecamera. Since photographs of the wave profile near breaking were also taken in the same films, the change of the wave profile near breaking was also examined. It was found that vertical distributions of horizontal water particle velocities at the crest and trough phases of breaking waves on beaches cannot be explained by the finite amplitude wave theories for uniform depth. Then, they were discussed in comparison with the breaker types. As a result, it was shown that the dimensionless vertical distribution of horizontal water particle velocity at the crest phase of breaking waves is determined by the combination of the beach slope and the deep-water wave steepness.

Numerical analysis of turbulent bottom boundary layers has been performed by applying the finite element method.At first, in order to check the validity of the numerical procedure, calculations for...

In this paper, a theory of the roll-wave trains in laminar water flow on a steep slope surface is developed by Dressler's method as the further research of the thin sheet flow.The analysis proves that if the discharge, the bed slope and the kinematic viscosity of water are given, then the solution is obtained uniquely and both wave and flow characteristics of the roll-wave trains can be determined.The experimental results obtained by the wave profile recorder are compared with above described theoretical ones, and the validity of this theory is recognized in good agreement.

In this paper, as the Ist. report of the studies on the thin sheet flow, the experimental results obtained by the wooden experimental flume, rectangular section of 40cm width and 19cm depth, with smooth surface are described.By this detailed experiment, the process of change of velocity distribution in transition from laminar flow to turbulent flow and the relation between Chezy constant, coefficient of frictional resistance and Reynolds' number are made clear, and the transition region is also determined. Moreover, the mean velocity formula in case of gentle slope is obtained.

As a breaking limit of progressive waves, many conditions have been proposed. One of them is that the water particle velocity at the wave crest is equal to the wave celerity.To examine this condition experimentally, the wave profile and the horizontal water particle velocity at the water surface near the crest of breaking waves were measured. These waves progress and break on a very gentle slope beach (1/200), which may be regarded as horizontal bottom.Experimental results of the wave profile and the horizontal water particle velocity at the water surface near the crest of breaking waves are presented and compared with theoretical values, and the breaking condition of progressive waves is examined experimentally.

Flow separation of a laminar boundary layer on the surface of a circular cylinder developed by monochromatic waves has been investigated both theoretically and experimentally, and next, characteristics of vortex formation and shedding have been discussed with Keulegan-Carpenter's number and Reynolds number, and finally, local depressions of the wave pressure around the cylinder induced by wake vortices have been examined in the experiment .

In the numerical method of prediction of wind waves in deep water, Hasselmann's nonlinear interaction theory is applied. This method assumes the energy balance of individual component waves. However, the total energy balance must exist in the transformation of irregular waves in shoaling water. In this investigation, experiments were carried out on the transformations in shoaling water of composite waves having two components and random waves having one or two main peaks. It was found that the elementary component wave height of the composite waves and the elementary peak power of the random waves decrease with decrease in the water depth. This reason can be explained qualitatively by the theory of the elementary component wave height change of finite amplitude waves in shoaling water. The secondary component wave height of the composite waves and the secondary peak power of the random waves increase with decrease in the water depth. This can be explained qualitatively by Hamada's theory of nonlinear interaction in uniform depth.

A solution of water particle velocities in the boundary layer developed by monochromatic waves on the surface of a circular cylinder is obtained by applying the boundary layer approximations and perturbation method to the Navier-Stokes and continuity equations represented in the cylindrical coordinates. Since, in this process, it is necessary to give the velocity outside the boundary layer, the water particle velocities of diffracted waves around the cylinder are derived from MacCamy-Fuchs' velocity potential. Moreover, the occurrence of laminar flow separation is explained by using this solution. On the other hand, using a hydrogen bubble tracer some experiments have been performed about the water particle velocities of diffracted waves, velocity profiles in the boundary layer and occurrence of wake vortices. These results are compared with theoretical ones.

This paper firstly describes two methods to measure vertical distribution and time variation of horizontal water particle velocity induced "by surface waves in a wave tank These two methods consist of tracing hydrogen bubbles and using hot film anemometers, respectively Secondly, the experimental results by the two methods are presented with the theoretical curves derived from the small amplitude wave theory, Stokes wave theory of 3rd order, and the hyperbolic wave theory as an approximate expression of the cnoidal wave theory Finally, based on the comparison of the experimental data with the theoretical curves, the applicability of the finite amplitude wave theories, which has been studied for the wave profile, wave velocity, wave length and wave crest height, is discussed from view point of the water particle velocity.

容器内で圓板が囘轉する場合の摩擦抵杭についての理論研究は,容器および囘轉圓板が滑かな場合についてSchultz-Grunowによつて行われた.本論文においては第I部において滑かな表面の容器内で粗面圓板が囘轉する場合を上記の論文の計算法と同樣の方法で取扱い,第II部において圓板と容器の間隙が非常に狹い場合の摩擦低抗のモーメントを求めた.第I部は第二の著者のすゝめにより第一の著者が計算した結果であり,第II部は第二の著者の考えで計算は第一の著者により行われた.