Cerebrovascular disorders such as cerebral aneurysms or atherosclerosis are reported to be caused by thedegeneration of arterial walls such that mechanical stresses induced by blood flow affects mass transport of theendothelial cells and then leads to hardening of arterial walls. In order to obtain a better understanding of thedegeneration of arterial walls, the authors have been developing a multi-scale and physics numerical simulation system “M-SPhyR (Multi-Scale and Physics SimulatoR) Circulation”. The paper presents the main features ofM-SphyR, which consists of three programs and the modules to connect three programs. The analyses are carried outfor three different cases: 1) multi-scale analysis for the cerebral arterial circle of Wills, 2) analysis of bloodflow-arterial wall interaction for a cerebral aneurysm, and 3) multi-physics analysis of atherosclerosis in the carotidartery. The results are compared to those by the conventional methods and are discussed for the further improvementof the simulation system.

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A review is presented on attempts to understand turbulence by using high-performance computing. An emphasis is puton the study of turbulence by the direct numerical simulation (DNS) of incompressible turbulence in a periodic boxwith the number of grid points up to 4096³. The DNS data shed some light on the basic questions on the statisticsof turbulence at high Reynolds number Re. The statistics include (i) the normalized mean rate of kinetic energydissipation in the limit Re→→, (ii) the energy spectrum in the universal equilibrium range, (iii) intermittency of thenergy dissipation rate, and (iv) energy transfer from large to small scales.

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Effective external disturbance levels of free-stream turbulence and acoustic noise are proposed to evaluate their influence on laminar-to-turbulent transition in 2-D boundary layers. These effective external disturbance level are defined as the product of experimentally measured external disturbance and a weight function, which has two parameters such as the center frequency and the band width. Those two parameters are optimized in boundary layers on an NACA0012 airfoil. In results, they are found out to be related to the growth rate of the primary instability predicted by e^N method based on linear stability theory.

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In the previous paper, the orientation of a long square bar in still water was investigated.The inclination angle of the bar was analyzed based on Archimedes' principle and the conditions of the existence of a solution. The correlations between the inclination angle φ and the specific gravity σ of the bar were obtained.The results were verified experimentally. In this paper, the sameanalysis is carried out for a long rectangular bar.The inclination angle of the bar φ is given by the width/height ratio of a section of α and the specific gravity σ of the bar.The orientation of the rectangular bar is classified on the map of α-α The orientation of a long rectangular bar is illustrated.

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[in Japanese]

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