A discrete vortex method which is developed for the numerical analysis of unsteady separated flow past a bluff body is presented. In this method, the flow past the body is assumed to be a potential flow except in the region of free shear layers which shed downstream from separation points. Then the free shear layers are approximated by discrete vortices and the body is represented by vorticity distributions. This method can be easily applied to the bluff body of complicated shape. The method is applied to the calculations of unsteady separated flows past a square prism, a circular cylinder and two bridge sections. The unsteady fluid forces acting on these sections in a stationary state or in motion are obtained. The calculated results are compared with experiments and a good agreement is shown.

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This paper reviews some processing methods in knowledge engineering and presents a private view about the applicability of knowledge engineering to fluid mechanics. Empirical problems which are desired to be solved by using knowledge engineering are shown and relating studies are refered. Some application systems which are developed by the authors are introduced as concrete examples. Then knowledge engineering ways of thinking, which are expexted to be fruitul, are suggested and some guiding recommendations to pursue studies in this field are made.

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A review is given on (1) the fundamental properties of the quantized vortex filament in superfluid ⁴He, (2) its dynamics, based mainly on the numerical calculation by Schwarz, and (3) the recent experiments by Avenel and Varoquaux on “phase slippage”, observed in superfluid ⁴He at ultralow temperatures, which is closely related to the creation and/or motion of the quantized vortex filaments.

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A finite-difference method to calculate the fluid flow with free surfaces numerically is proposed. This method is an extension of MAC (marker and cell) method, and two-dimensional, axisymmetrical or three-dimensional complex fluid flows with the surface tension effect can be calculated effectively. Numerical calculations are carried out for the collision of liquid drops, for the collision of a liquid drop with a rigid wall and for a splashing of a liquid drop.

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A two-dimensional unsteady laminar flow is numerically simulated when a pair of rectilinear vortices translates perpendicularly to a non-slip infinite plane wall in an incompressible viscous fluid. Using the finite difference approximation of 3rd order accuracy the governing vorticity and streamfunction equations are discretized and the fiow is numerically integrated with R_e=5000 and 10000 subject to the appropriate boundary conditions from the initial state prescribed. The Reynolds number Re is the circulation of the vortex divided by the kinematic viscosity of fluid. The illustration of the calculated results simulates well the rebounding of the primary vortex and the motion of the secondary vortex which is released by the interaction of the primary one with the boundary shear layer. The stagnation pressure is also evaluated, whose magnitude is observed to be considerably influenced by the presence of the secondary one.

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