New numerical solutions of the capillary-gravity wave problem are reported with a special emphasis on the bifurcation diagrams and their complicated structure. We restrict ourselves to the study of stationary, periodic, and two-dimensional waves. None the less for this simplification, we will show that the full understanding of the bifurcation structure is very far from being complete.

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Tsunamis generated by sea bottom movement due to earthquakes are described from several viewpoints of phenomena and analysis. The initial profile is not always uniquely estimated, because fault parameters of an earthquake are not uniquely determined, and because there is a possibility of sea bottom movement which is not directly related to fault parameters. Basic equations in numerical simulation are switched from the linear theory in deep sea to higher order theories in shallow sea and on land. Several criteria other than the CFL condition are necessary to keep stability and accuracy of numerical simulation. Although runup heights numerically obtained are considered accurate enough for practical application, other properties such as wave profile, current velocity, wave pressure and so on are not yet satisfactorily solved. The 1983 Nihonkai-Chubu earthquake tsunami revealed many different faces, to edge waves for which there is no theory applicable.

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Systematic studies on ocean surface waves (wind waves) have been started in the 1940's, which is roughly one century later than the start of the studies on water waves. Since then rapid progress has been done in the studies of ocean surface waves; Now we can predict ocean waves in a global scale with practically sufficient accuracy. However, there still remains many fundamental problems in the dynamical process of ocean surface waves. Recent studies on the dynamics of ocean surface waves are reviewed. The major topics discussed in the present paper are initial generation of wind waves, energy transfer from the wind to wind waves, nonlinear energy transfer among spectral components of wind waves and energy dissipation due to wave breaking. These are fundamental components in the spectral energy-balance equation which is used for practical prediction of ocean surface waves.

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Velocity fluctuations in the near region of initially turbulent axisymmetric jets have been examined mostly through frequency spectrum analysis. Frequency-centered activity was observed even in the jet issuing from a fully-developed turbulent pipe flow. The dominant frequency monotonously decreased with increasing the axial distance from the jet exit plane; there was no preferred periodicity scaled with pipe diameter. The frequency of the artificially introduced disturbance which reached the maximum amplitude at a certain axial location, agreed favorably with the natural dominant frequency at that location. For the jet which had a thick turbulent boundary layer at the jet exit plane, the dominant frequency approximately scaled with local momentum thickness. These results are basically consistent with the notion of Petersen & Samet [J. Fluid Mech. 194 (1988)], that the basic mechanism responsible for the jet preferred mode is a shear-layer type of instability of velocity profile.

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Boundary-layer over a swept wing is fully turbulent near the leading edge region owning to the crossflow instability. Swept cylinder model provides us a similar flow field where we could do some fundamental study on three-dimensional boundary-layer transition.
In the present paper, three-demensional (3-D) transition mechanism in swept cylinder boundary-layer is studied experimentally using an effective smoke visualization technique and a hot wire measurement. Transition Reynolds number for the crossflow instability is found to be comparable to the previous value. Smoke visualization showed detailed crossflow structure and high frequency secondary instability riding over crossflow vortices. Hot wire measurement by 3-D traverse system made possible to measure U (y) profile which is strongly modified into sinusoidal variation. Traveling disturbance (1KHz) is also detected in the transition region. It was detected that rapid growth in turbulence intensity begins not at the critical point for the stationary instability (primary instability), but at the critical point for unsteady instability. As a result, by drawing an schematic picture for the complicated transition process, some guidelines for future Laminar Flow Control study on an Airbus wing are provided.

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In order to create the transition criteria, or to control 3-D boundary layer flow, it is essential to know the detailed transition mechanism in advance. The main purpose of the present investigation is to make it clear the turbulent transition process in a swept cylinder boundary layer, which gives important fundamental information not only in the field of airbus drag reduction, but also in the field of space plane aerodynamic heat control.
Liquid crystal film is utilized to measure the transition region and streamwise streaks which corresponds to the crossflow vortics are visualized in color variation. These visualized color streaks enable us to find out the relation between velocity field and heat transfer rate which gives important fundamental information for aerodynamic heat effect on a swept wing or a delta wing surface. Detailed 3-D velocity measurement has been also performed using three-dimensional traversing equipment and rotatable hot wire.

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