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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渦輪は並進運動に伴ってWidnall instabilityと呼ばれる渦核の軸方向に波状変形するが, 本報告はその波状変形の波の数に着目した実験的研究である。今回, 煙可視化方法によりレイノルズ数 (Re数) が2600の渦輪の様子を時空間的に詳細に観察したところ, 渦輪の並進運動に伴いその波の数が減少することを見出した.そして, この波の数が減少する遷移状態の様子も捉えられた.

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本論文は負の浮力を持って斜面上に表層放流される流れにおける潜り点の水理条件に関する実験的検討結果を示すものである.貯水池密度流の問題は, 環境水理学上の重要性から多くの研究者によって取り上げられてきたが, 潜り点の水理条件に関する研究結果は相互に異なるものであった.本研究はその原因を実験的に明らかにしようとするものである.潜り点近傍の流況は4種に分類しうること, また観察された各種タイプの流れのメカニズムは大きく異なるものであることが実験的に明らかになった.考察の結果, この様に異なるタイプが水理条件に応じて出現することが従来の相互に異なる研究結果の原因であるとの結論を得た.さらに放出密度フルード数-斜面勾配の平面上で, 潜り点の水理条件についての3次元の推定図表を実験結果に基づいて提案した.

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下面を加熱した水平長方形ダクト内の混合対流の3次元線形不安定性を調べる.ダクトの垂直壁の温度条件は完全熱伝導と仮定する.線形撹乱方程式の解を2重チェビシェフ多項式展開し, 選点法を用いると, 本問題は行列の一般化固有値問題に帰着する.これを数値的に解いて, 横ロールの臨界レイリー数を求めた.その結果, 横ロールの臨界レイリー数は基本流のレイノルズ数の増大とともに増大し, 臨界レイノルズ数以下の低レイノルズ数領域では, 横ロールの臨界レイリー数が, 2次元流れ場の解析で与えられる縦ロールの臨界レイリー数を下回ることが示された.また, この臨界レイノルズ数を, アスペクト.A=1, 2, 4, プラントル数Pr=0.71に対して確定した.

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