ABSTRACT

This paper investigates the flow through and around a square array of cylinders. The investigations were performed numerically by RANS simulation with kω-SST turbulent model using OpenFoam. The effects of volume fraction on the drag coefficient have not been studied completely yet. The Reynolds numbers is Red = 4.1×103, volume fraction ranges from 0.13 to 0.5. The results show that the drag force distribution within the array of cylinders is influenced significantly by volume fraction. The drag coefficient increases with volume fraction, and unexpectedly the drag coefficients of some cylinders within the array are larger than that of a single cylinder, which should receive attention in real practice. At low volume fraction, the flow field is dominated by small scale vortices, however with the increase of volume fraction, the small scale vortices are attenuated and large scale vortices are dominant.

INTRODUCTION

The pile-group foundation is widely used is real practice. It is of importance to accurately estimate the current force on the piles as well as understand the flow filed around and within the piles. Flow around the piles is complicated due to the interaction among piles, and the force characteristics and flow field have not been investigated completely yet. Therefore, it is necessary and valuable to investigate the current force and flow field for the pile-group foundation.

The classical problem of flow around a circular cylinder has been broadly investigated due to its practical importance in engineering applications. For example, experiments have been carried out by Tritton and D. (1959), Roshko (1961), Sabersky and Acosta (1964), Schewe (1983), Sumer and Fredsøe (1997), Graf and Yulistiyanto (1998) and numerical studies on the subject have been conducted by Breuer (2000), Travin et al. (2000), Catalano et al. (2003), Pattenden et al. (2005), Liang and Papadakis (2007), Grigoriadis et al. (2010), Lysenko et al. (2013), Perković et al. (2013). The relationship between the drag coefficient and Reynolds number, and the flow field characteristics under different Reynolds numbers are the main foci in the above studies.

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