Many turbulent flows of interest to mechanical and aerospace engineers are compressible, and we need to know whether turbulence models developed in incompressible flows can be relied on in compressible flow, or whether their coefficients need to be made functions of some suitable compressiblity parameter. Now the coefficients in a turbulence model are related to, and in some cases actually equal to, the parameters used to describe turbulence structure. Therefore the real question is whether the structure parameters are affected by compressibility. In this paper our current knowledges will be reviewed, with the needs of modeling in mind.

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A new approach toward a universal numerical solver for solid, liquid and gas is proposed. By this method, dynamical evaporation process of metal can be directly calculated. The simulation of this process has been beyond the capability of conventional scheme because of the difficulties in treating 103 times density difference and large deformation of surface. The CIP method can describe a sharp interface with one grid and is able to describe incompressible and compressible flow all together in one procedure. The principle of the CIP method is illustrated and possible application area is proposed.

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Generation and propagation mechanism of tsunamis are summarized including the recent research topics : inversion method, “tsunami earthquakes”, and new techniques of numerical simulation. Multi-fractral dimension is proposed to find the critical grid size in a given geometry for tsunami simulation. Finally, the visualization of tsunamis is introduced in order to provide information as well as impression through the advanced tools in computer graphics. The venture

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Turbulence and two-dimensional channel turbulent flow in the system rotation are explained. Rossby number is the most important parameter in a rotating fluid. The effect of rotation is indicated by the ratio of the background vorticity to the shear vorticity in a rotating turbulent shear flow. Rotation such that shear becomes cyclonic is stabilizing, but anticyclonic rotation is destabilizing for low rotation rates and restabilizing for higher.
Fundamental relations induced through Navier-Stokes equations and a decaying turbulence in the presence of rotation are discussed. For a two-dimensional channel flow the laws of velocity distributions are also discussed by the dimensional consideration with experimental results.

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Since lung sounds are physiological signals which anybody can acquire safe and free without any limitations, it is quite an achievement if one can extract any useful information from them. Auscultation of the lung has been a basic diagnostic tool for a physician, and there are many auscultatory findings which we know, yet the origin of which we do not know. For instance, normal breath sounds heard over the neck are louder in expiration than in inspiration, while those heard over the lower chest are louder in inspiration than in expiration. The former is probably due to the narrowing of glottis during expiration, but the latter is more complicated. The structure of the airways and the direction of the flow could be closely related, but we do not know exactly how. Flow limitation during forced expiration has been one of the hottest issues in respiratory physiology for many years. It is generally agreed that an airway collapse is the cause of flow limitation, but what causes the airway collapse? Is it possible for the vortices or other secondary flows developed rapidly in the airway during forced expiration to cause a significant pressure drops in the airway? We do not know the answer and we would like to know it either way, hopefully in near future.

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The circumferential waviness of a vortex ring is a well-known phenomenon called Widnall instability. An experimental study of the number of waves of a vortex ring at Re=2600 is presented. By means of smoke visualization technique, the spatial and temporal development of the vortex ring was examined in detail. It was found that the number of waves decreases successively through a transition state as the ring propages downstream.

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This paper presents the experimental study on the plunging conditions of the negative surface buoyant jet discharged on the sloping bottom. As well known, various results has been reported by several researchers on the plunging conditions. The purpose of this study is to clarify the reasons for these various results. The experiments revealed to be able to classify the flow field into four flow types. Flow mechanism of each flow type was investigated, and this paper concluded that the various results of previous studies were caused by different flow types. This paper also proposed three-dimensional diagram on the plunging conditions on Bottom slope-Densimetric Froude number at outlet plane.

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The linear instability of mixed convection in a rectangular duct heated from bellow is investigated. The side walls are assumed to be perfectly conducting. The eigenvalue problem is formulated by making use of a double expansion method in Chebyshev polynomials and a collocation method. The resulting generalized eigenvalue problem is solved numerically. It is found that the traveling transverse roll is the most unstable disturbance when the Reynolds number is less than a certain critical value, while the longitudinal roll is most dangerous when the Reynolds number is larger than the critical value. The values of the critical Reynolds number are determined for the aspect ratios A=1, 2 and 4 and the Prandtl number Pr= 0.71.

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