Theory of Flow on Road Surface

By solving the momentum equation of a thin sheet flow on road surface numerically with the condition of continuity obtained under the condition that rain falls on road uniformly, water depth and mean velocity of thin sheet flow and also frictional velocity related with soil-erosion of road surface are computed, and then the effects of camber shape and longitudinal slope of road surface on its drainage and stabilization are discussed

On the Analysis of Mechanism of River-Bed Variation by Characteristics

In this paper, a new method using the characteristic curve for analysing the mechanism of river-bed variation in a river in which the sediment is mainly transported as bed-load is presented. This method is introduced on the basis of the assumption that both of stream flow and river-bed profile vary gradually and the computation of river-bed variation is proceeded step by step. Various interesting phenomena of river-bed variation resulting from the sediment transport can be explained clearly by this characteristics method. As some examples, the deformations of mound and depression of river-bed in uniform flow of water and the deposition of sediment in reservoir are treated, and then the mechanism of their behaviours are ascertained

Representation of Water Particle Velocity of Breaking Waves on Beaches by Dean's Stream Function

Experimental values of water particle velocity of breaking waves on uniformly sloping beaches differ considerably from the theoretical values of Stokes waves of the third order and cnoidal waves of the second approximation. In this paper, Dean's stream functions are calculated by giving simultaneously measured time variations of the water level of the breaking waves. Vertical distributions of horizontal water particle velocity at the crest phase, calculated by using these stream functions, are compared with experimental distributions in order to discuss the applicability of Dean's stream function method. These theoretical distributions can explain the experimental results well, although this stream function method assumes permanent waves in uniform depth. Dean's stream function can express an asymmetric wave profile as that of breaking waves on sloping beaches, while the Stokes wave theory has a symmetric wave profile. It is suggested that the breaking wave profile dominates the water particle velocity field of breaking waves

Hydrodynamic Forces on a Circular Cylinder Placed in Wave-Current Co-existing Fields

The in-line hydrodynamic force acting on a circular cylinder in a wave-current co-existing field and its generating mechanism are discussed. This study focuses on the asymmetries of both the water particle movement and the resultant vortex property with respect to the cylinder as being the causes of an inherent generating mechanism of the hydrodynamic force in the wave-current co-existing field. First of all, the vortex property around a circular cylinder in the wave-adverse current co-existing field is examined by flow visualization tests. It is found that the vortex property depends on the flow characteristics around the trough phase when the wave-current composite velocity becomes maximum and can be represented with a newly proposed K.C. number for the co-existing field. Next, the characteristics of the in-line force are made clear by evaluating the drag coefficient and the mass coefficient in the expanded Morison's equation for the co-existing field. These coefficients can be well arranged by (K.C.)₂, which is one of the newly proposed K.C. numbers, and their characteristics coincide with the existing results in the wave-only field. The in-line hydrodynamic force in the co-existing field can be explained sufficiently by considering the vortex property in the same manner as clarified in the wave-only field

Harbor Oscillations Induced by Composite Waves in Rectangular Basins

This paper presents the results of experiments on harbor oscillations induced by composite waves in rectangular basins with a constant depth. The experiments were carried out in a two-dimensional wave tank in which a fully open harbor model was installed. In order to obtain the constant wave height the wave period was kept constant through a series of the tests but the harbor length was variable. The wave records were taken at both harbor entrance and end, and the wave amplification factor, defined as the ratio of the wave height in a certain point to that of standing waves when the entrance was closed, was derived for both regular and composite waves by the harmonic analysis. The result of comparison between the response curves for regular and composite waves, shows that the resonant characteristics by composite waves is different from that by regular waves by mutual interaction of component waves, especially at resonant modes

ESTIMATED VALUES OF BOTTOMFRICTION FACTORS OF SOME JAPANESE COASTS

In order to forecast shallow water ocean waves, the value of the bottom friction factor in shallow water has to be given for estimation of wave energy loss due to bottom friction. In this paper, from the damping of the significant wave heights and the transformation of the wave spectra observed off some Japanese coasts, the bottom friction factors are computed and the relationship between the bottom friction factor and the wave Reynolds number is presented. It should be noted that the estimated values of bottom friction factors of some Japanese coasts are much greater than 0.01, which was given by Bretschneider to be generally used in forecasting shallow water ocean waves