Numerical Simulation of Two-Phase Transient Flow Around Two Side-By-Side Circular Cylinders and Select Appropriate Turbulence Model Based on Vortex Shedding Frequency

Subject Areas : Article frome a thesis

Abolfazl Aslani Kordkandi ¹ , Meysam Bayati ² , Freydon Vafai ³ , Aref Farhangmehr ⁴

1 - Department of Engineering, Payame Noor University (PNU), P.O. Box 19395‑4697, Tehran, Iran.
2 - Former M.Sc. Student of Marine Structures, K.N. Toosi University of Technology, Tehran, ‎Iran.
3 - Associate Prof. of Marine Structures, Department of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran.
4 - Former M.Sc. Student of Marine Structures, K.N. Toosi University of Technology, Tehran, ‎Iran.

Received: 2019-12-04 Accepted : 2023-02-19 Published : 2023-01-21

Keywords: Numerical Simulation of two, phase transient flow around two side, by, side circular cylinders,

Abstract :

Abstract
Introduction: Nowadays, scouring is one of the important issues in river engineering as well as coastal ‎engineering. Based on the results of the investigations, the destruction of most of the bridges ‎built in the rivers is due to scouring around piers. For this reason, it has been the subject of ‎many researches conducted in recent years‏.‏ ‎ Investigation of the flow pattern around the piers ‎gives a more accurate understanding and vision for scouring prediction.‎
Methods: The flow pattern around two side-by-side circular cylinder with various gaps are investigated numerically in current study. The numerical calculations are carried out on quadrilateral mesh which is finer close to the cylinders vicinity in order to provide better description of boundary layer and gradually become coarser further places. In term of simulation of the free surface effect, the volume of fluid (VOF) method used. In this simulation based on the frequency of vortex shedding and Strouhal number. After selecting appropriate turbulence model (RNG k - ε) the value of velocity, turbulence and bed shear stress reported.
Findings: The results show that by reducing the gap between two cylinders, the velocity in middle of cylinders increases and the maximum velocity observed in G/D=1.5 while for smaller gaps (G/D<1.5) the velocity decreases due to blockage. In case of two side-by-side cylinders turbulence intensity in the middle of channel is higher than in bed which represent the significant impact of vortices. However, in case of single cylinder turbulence intensity in the bed of channel is higher than those of in middle which represent the significant impact of bed on turbulence intensity.

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