Abstract
The trapezoidal beam structure is ubiquitous in giant engineering equipment, while their aerodynamic characteristics have not been clearly understood. Numerical simulation method was adopted to investigate the flow around two tandem identical trapezoidal cylinders. The study was conducted using a Reynolds number of 2.2 × 104, and with a spacing ratio varying from 0.5 to 10. The incompressible two-dimensional finite volume method was used for solving Reynolds-Averaged Navier–Stokes (RANS) equations with realizablek−εmodel. The effects of cylinder geometry and spacing between the cylinders on aerodynamic characteristics, unsteady flow patterns, time-averaged flow characteristics, and flow instability was studied. The results show that the flow around the two tandem trapezoidal cylinders is highly dependent on the spacing ratio. The flow modes can be classified into: extended-body regime (Mode I,S∗ ≤ 1), reattachment regime (Mode II, 2 ≤ S∗ ≤ 3), and binary regime (Mode III,S∗ ≥ 4). We explored their respective flow characteristics and distinctions through the force/pressure coefficients, time-average streamwise velocity, and the flow field evolution.
Highlights
Mathematical Problems in Engineering smaller trapezoid bottom width
Cheng and Liu [5] studied the influence of rear-to-front width ratio (λ) from 0 to 1 on the flow characteristics. e results show that λ = 0.5 makes the separation state of the shear layer and the wake vortex have the opposite trend. is means, when λ < 0.5, the vortex shedding frequency increases with the increase of λ, but when λ > 0.5, the frequency showed a negative correlation with the width
The numerical simulation of the flow was carried out around two identical trapezoidal cylinders in a tandem arrangement at Re 2.2 × 104. is study investigated the interference of flow past two tandem trapezoidal cylinders at different spacing ratios of S∗ 0.5–10. e aerodynamic characteristics, wake flow, and vortex shedding patterns of the two cylinders were considered. e spacing ratio had a significant effect on the flow field around two tandem identical trapezoidal cylinders
Summary
Was 10D, and the distance from the center of the downstream cylinder to the outlet was 20D. e spacing ratio S∗ was defined as S∗ S/D, where S represents the distance between the rear face of the upstream cylinder and the front face of the downstream cylinder. E calculation boundary conditions for the flow field were set as follows: Reynolds number: 2.2 × 104. In order to ensure the accuracy of the numerical simulation, the flow around a square and around a trapezoidal cylinder at Re = 2.2 × 104 was calculated first. E drag coefficient for the calculation of the flow around the square-cylinder measured in this study was consistent with the experimental results of Lyn et al [23] and Norberg [24]. It can be seen that the numerical simulation performed in this paper is accurate and reliable In both cases, grid thickness of the first layer near the cylinder surface was less than 3.6%, which was consistent with the literature value. Considering the computational cost of the calculation example, grid thickness of the first layer was determined as Δd 0.0355D in this paper for subsequent calculations
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