Hydrology as a field of modern science began in early 1930's, when Sherman (1932) proposed the unit-hydrograph method, a kind of response system theory, and Horton (1933) developed a theory on surface runoff generation based on a simplified vertical infiltration process. Since then, hydrology saw its renewals every 15 to 20 years ; i. e., dynamic hydrology started in 1950's and stochastic hydrology in mid-1960's.
Now, hydrology is experiencing a new wave of physical hydrology which is constructed based on the physics of the saturated and non-saturated two- or three-dimensional infiltration process. Examples from the recent advancements in hydrology are described. An establishment of “variable-source-area” concept is one of its great achievements.

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Theoretical studies on the motion of the red blood cell in the blood flow are surveyed, in relation to the recent advance in experiments. One of the most realistic models for the red blood cell, which contains a viscous fluid interior enclosed by a flexible membrane, has enabled detailed description for the peculiar behavior of the red blood cell in microvessels and in shear flow. For quantitative comparison between theory and experiment, there is a need for the development of theoretical analyses including asymmetric flow in microvessels and cell motion under cell-cell interactions.

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Chemical engineering embraces a broad field of diversified activities growing out of materials processing. Materials processing requires the use of a series of distinct operations. For example, if the materials are impure, they are purified first if necessary, and if they are mixtures, they are separated into fractions, some of which are useful in further processing whereas the others are discarded. Generally the process includes one or more chemical reactions and, in most cases, the materials are fluids. Most operations such as reaction and separation may require the transfers of heat and mass, so that the subject of transport phenomena ranks along with thermodynamics as one of the key engineering sciences in chemical engineering. Film theory is discussed as an example of the typical analytical approaches in the transport phenomena in chemical engineering. Although this model is physically unrealistic, it has nevertheless proven very useful as a basis for correlating heat or mass transfer coefficient in terms of a simple physical picture.

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This review consists of 5 sections. Section 1 summarizes the meaning of the pioneering work by L. F. Richardson. Section 2 discusses the basic role of the quasi-geostrophic theory. The nonlinear instability peculiar to the nonlinear system is also emphasized there. In Section 3, Arakawa's glorious work which broke through the difficult situation mentioned in Section 2 is emphasized and it is pointed out that most of the general circulation models were built by Japanese scientists. In Section 4 the present status of the numerical weather prediction is surveyed and problems in the future are discussed in Section 5.

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In the surf zone, velocity, pressure fluctuation and suspended sediment concentration are measured near the bottom. Fundamental data are obtained for the mean suspended sediment concentration, phase lag between onshore velocity and suspended sediment concentration, and the suspended sediment transport rate. Near-bottom velocity distributions under a finite amplitude wave are calculated on the basis of the turbulent boundary layer theory. Concentrations of reference level are estimated after Kalkanis' theory using the velocity value at the top of sand particle and distributions of suspended sediment concentration after turbulent diffusion theory. The phase lag computed agrees with that observed.

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A vortex ring at an interface of the density stratified flow behaves complicatedly and plays an important role in entrainment. When the vortex ring ascends through the density interface, secondary vorticity is generated on the surface of the vortex ring not only by the discontinuity in velocity between inside and outside of the vortex ring, but also by the difference between the direction of the gravity force and the density gradient. In this study, we estimated theoretically newly generated secondary vorticity constituting a vortex sheet over the surface of the vortex ring and integrated it over the surface of the vortex ring. Then the vortex sheet is divided into many circular vortex filaments and the deformation of the vortex sheet was calculated by investigating the motion of the filaments. From this analysis, it is found that negative circulation consentrates on doubly piled parts around the surface of the original vortex ring and the calculated results agree well with the experimental observation.

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In order to clarify the aerodynamic characteristics of a ski-jumper in the forward-leaning position, wind-tunnel measurements are made of the lift and drag forces acting on a scaled-model human body, and the flow around the model is observed by using tufts, at various angles of incidence. Effects of the surface roughness are also examined to find that small roughness can increase the lift as well as the drag without essentially changing the lift-to-drag ratio, and thus can improve the aerodynamic characteristics. Various interesting features of the characteristics including the roughness effect are discussed in terms of the flow structures observed.

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