Developing compressible viscous fluid flow in a curved duct, especially mechanism of the voritical flow field due to the curvature, is studied numerically by means of DNS. The Dean number of Dn=271 and the Mach number of M=0.7 are chosen to investigate the curvature effects on the compressible viscous flow. The secondary flow is defined as the helicity density structure, which leads to a clear relationship between the secondary flow pattern and the three-dimensional structure downstream. Higher Mach number flow yields more complicated secondary flows, a pair or two pairs of Dean vortices are generated downstream at the same Dean number. DNS results show a developing helicity density flow of the herical structure. Convection terms in the Navier-Stokes equations are visualized as vector plots, as well as the pressure gradient. This visualization leads a clear understanding of the role of viscous terms near the outer wall. Numerical unsteady motions responding to random disturbances show temporal periodic oscillation of the spanwise velocity component near the outer wall of z=0.

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The issue of whether propulsion in swimming is due primarily to lift or drag appeared to have been settled in the early 1970s. Prior to that time it was believed that the best way to propel the body forward was to pull the hand directly backwards to use drag forces. In addition, the actual motion of a hand in swimming is obviously unsteady and the time-dependent fluid forces called the “dynamic lift” have to be taken into account. In this study, unsteady fluid forces acting on a disc simulating a human hand and the vortical flow field were investigated in the (sinusoidal) pitching motion. The wind tunnel test using the three-dimensional model is effective for understanding the relationship between the dynamic lift and the fundamental structure of the vortex system. It is confirmed that the pitching motion is available for keeping lift higher after the separation occurs. The delay of stall is observed and also a much larger lift force than the quasi-steady-state value is obtained in the pitching motion. The dynamic lift acting on a pitching disk is strongly influenced by vortices shed from the outer edge of the disk. The lift force becomes larger as the vortices develop and the dynamic stall occurs at the instance of collapse in shape of the vortices.

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A method for inferring the spatial distribution of sea-salt emission flux in surf zone from the volume-size concentrations of sea-salt particles observed near at sea shore is discussed. This method applies the boundary integration method (the collocation method) on the transport and diffusion equation for sea-salt particles. Two approximate influence functions are introduced, of which main difference is concerned with whether including the horizontal eddy diffusion effect. The estimation of the spatial distributions of sea-salt flux from the observed volume-size concentrations is generally an ill- posed inverse problem, so that the following disposals are necessary; (1) reducing the sensitivity of an estimation to data error by use of the multi reference data at the multi levels of height lower than 15m from surface, (2) assimilating the reference data to those computed by the model equations within an allowable limitation. The locations of effective flux sources and a tendency of time variation of flux strength inferred from the reference volume-size concentrations approximately coincide with those estimated by the wave simulation (SWAN).

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Ring-like ripples with wavelength about 1 cm appear on the surface of icicles during ice growth from a thin film of flowing supercooled water. This phenomenon is treated as the problem of morphological instability of solid-liquid interface during crystal growth from a thin shear flowing liquid with one side being a free surface. The length scale of the ripples is determined by a linear stability analysis of the interface, and a new mechanism of ripples formation is proposed.

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Chapt.2 describes LISBON LDA Symposium and basic optical techniques citing the ideas of instrumentation.

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