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Tetsuro Tamura ORI, Shimizu Corporation, 2-2-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo 100, Japan Egon Krause Aerodynarnisches Institut, RWTH Aachen, WOllnerstraBe zw, 5. u. 7, Aachen, West Germany Susumu Shirayarna and Katsuya Ishii Institute of Computational Fluid Dynamics, 1-22-3 Haramachi, Meguro-ku, Tokyo 152, Japan Kunio Kuwahara The Institute of Space and Astronautical Science, 3-I-1 Yoshinodai, Sagamihara-shi, Kanagawa 229, Japan

This paper presents numerical investigation of the interaction of multiple three dimensional gas bubbles rising in a square cylinder using the volume of fluid method (VOF) including surface tension effects. Bubble trajectories, dynamics, shapes, and wake interaction are discussed.

A vast amount of investigations has been carried out for the flow around a circular cylinder. While there are very few were concerned about flow around rectangular cylindrical structures. For flow around a rectangular cylinder, experimental results showed that flow patterns and hydrodynamical forces such as lift, drag and St are strongly dependent on both Reynolds number (Re) and the side ratio of the cylinder’s crosssection. In the range of Re between 102 and 2.0 X 103, the St of a square cylinder shows a slight and continuous change around a constant value. Whereas for flow around a rectangular cylinder with B/A = 2, St varies with Re. Re has little influence on St when it’s greater than 2000 [1,3]. Some researchers have conducted 2-D numerical simulations of flow around a rectangular cylinder in the past, 3-D simulation, however has not been developed. It has been found that a 2-D model can provide accurate results only for Re up to 300 [2,5]. Therefore 3-D simulations are necessary for flow around a rectangular cylinder at higher Re.

A square cylinder is one of the most commonly employed shape in the study of the galloping type of flow induced oscillation because most buildings have either square or rectangular cross sections and because the square cylinder is susceptible to both galloping and vortex resonance, thus making the problem complicated and challenging. Many researchers had already carried out measurement on forces and pressure acting on a transversely oscillating square cylinder. Some of the author’s own measurement had been reported in Bearman and Luo [1]. The objective of the present paper is to carry out flow visualization on a transversely oscillating square cylinder to gain more understanding of the flow and make comparison with the author’s own measurement.