Numerical simulation of the flow past six-circular cylinders in rectangular configurations

Abstract

Two-dimensional numerical simulations of the flow past six cylinders in the 2 × 3 matrix configuration and 3 × 2 matrix configuration are performed at a low Reynolds number (Re = 100) to provide a comprehensive understanding of the complicated physics for flow past multiple cylinder arrays. The spacing ratio L/D is varied from 1.25 to 7.0 (where L is the distance between the adjacent cylinder centers and D is the diameter of the cylinder). The effects of spacing ratio on the flow pattern, force coefficient, pressure distribution, and Strouhal number are investigated. The underlying flow physics for flow past six-cylinder arrays are interpreted from the view of shear layer development and force characteristics. Depending on the spacing ratio, four wake flow regimes are identified: a single bluff body flow regime (L/D = 1.25), shielding flow regime (1.5 ≤ L/D ≤ 2.5), reattachment flow regime (3.0 ≤ L/D ≤ 4.0), and co-shedding flow regime (L/D ≥ 4.5). For both configurations, regardless of L/D, the mean force coefficients on the downstream cylinders are always smaller than those of upstream cylinders, and an abrupt change of the standard deviation of the force coefficients is observed during the transition of different flow regimes. The Strouhal numbers of the six cylinders generally increase with L/D, and approach to that of a single cylinder in the co-shedding flow regime, a broadband FFT spectrum with multiple peaks is observed in the shielding and reattachment flow regimes.