Empirical Investigation of Flow Interferences and Aerodynamic Behaviors of Three Squared-section Cylinders in an Equilateral-triangular Arrangement Subjected to Cross-Flow and Various Distance Ratios

This research is an attempt to investigate wind tunnel tests to measure the minimum values of force coefficients in three cylinders of identical squared sections in an equilateral-triangular arrangement when subjected to a cross-flow. These tests were conducted for seven spacing ratios varying from 3.1 to 1.1 at subcritical Reynolds number of 1..7*3.4. The pressure is measured by an electronic pressure transducer on each cylinder surface. Some applications of multi-cylindrical structures include sky scrapers, chimneys, cooling systems for nuclear reactors, coastal structures, heat exchanger pipes etc., where the only way to model the flow through the structure is to apply multi-cylinder arrays subjected to a cross-flow. Studies on triple cylinder systems may contribute to recognition of more complex flows within arrays with more extended cylinders. For the current arrangement, when the cylinders dimensions are in such a way that l/d=1.1, it is observed that contributions of flow interference among the cylinders are attenuated and pressure coefficient distribution over upstream cylinder is almost similar to that of a single cylinder which is in a good agreement with the reported results by Otsuki et al. measured for a single cylinder at Re=6*3.4. Generally speaking, in an equilateral-triangular arrangement, the average lift coefficient of upstream cylinder is higher than those in downstream cylinders. Furthermore, for l/d>2, an increase in lift coefficient is evident for all cylinders. Variations of l/d ratio strongly affect flow patterns around the cylinders as well as aerodynamic coefficients. In addition, the effect of flow interferences among the cylinders is fairly decreased when l/d ratio increases.

Keywords:

multi-cylinder arrays , equilateral-triangular arrangement , aerodynamic flow , pressure distribution , spacing ratio