Raheela Manzoor

Numerical investigation of fluid-solid interaction for flow around three square cylinders

In this work, fluid-solid interactions are numerically investigated for flow around three equally/unequally spaced square cylinders using the lattice Boltzmann method. Two major trends of shear layers observed for equal gap spacings between cylinders: (i) without roll up (W), and (ii) with roll up (R). While for unequal gap spacings, four major trends of shear layers observed: (i) without roll up in both gaps (WW), (ii) without rollup in first gap and with roll up in second gap (WR), (iii) with roll up in first gap and without roll up in second gap (RW), and (iv) with roll up in both gaps (RR). g = 3 is found to be the critical equal spacing value. Also g = 1.5 is found to be suitable equal spacing in terms of minimum drag force. While the suitable unequal gap spacing combinations found in this study are (g1, g2) = (1.5, 0.5), (g1, g2) = (3, 0.5) and (g1, g2) = (5, 0.5). Results show that flow induced forces can be suppressed by suitable unequal gap spacing combinations.

Transitions in the flow patterns and aerodynamic characteristics of the flow around staggered rows of cylinders

A two-dimensional numerical study of flow across rows of identical square cylinders arranged in staggered fashion is carried out. This study will unreveal complex flow physics depending upon the Reynolds number (Re) and gap spacing (g) between the cylinders. The combined effect of Reynolds number and gap spacing on the flow physics around staggered rows of cylinders are numerically studied for 20 ≤ Re ≤ 140 and 1 ≤ g ≤ 6. We use the lattice Boltzmann method for numerical computations. It is found that with increase in gap spacing between the cylinders the critical Reynolds number for the onset of vortex shedding also increases. We observed a strong effect of Reynolds number at g = 2 and 4. Secondary cylinder interaction frequency disappears for large Reynolds number at g = 6 and 5 and the flow around cylinders are fully dominated by the primary vortex shedding frequency. This ensures that at large gap spacing with an increase in the Reynolds number the wakes interaction between and behind the cylinders is weaken. Furthermore, it also ensures that the wake interaction behind the cylinders is strongly influenced by the jets in the gap spacing between the cylinders. We also found that g = 2 is the critical gap spacing for flow across rows of staggered square cylinders for the considered range of Reynolds number. Depending on the Reynolds number we observed; synchronous, quasi-periodic-I, quasi-periodic-II, and chaotic flow patterns. In synchronous flow pattern, an in-phase and anti-phase characteristics of consecutive cylinders has been observed. The important physical parameters are also analyzed and discussed in detail.

A computational study of drag reduction and vortex shedding suppression of flow past a square cylinder in presence of small control cylinders

This article presents a two-dimensional numerical study of the unsteady laminar flow from a square cylinder in presence of multiple small control cylinders. The cylinders are placed in an unconfined medium at low Reynolds numbers (Re = 100 and 160). Different flow phenomena are captured for the gap spacings (g = s/D, where s is the surface-to-surface distance between the main cylinder and small control cylinders and D is the size of the main cylinder) between 0.25 – 3 and angle of attack (θ) ranging from 300 to 1800. Numerical calculations are performed by using a lattice Boltzmann method. In this paper, the important flow physics of different observed flow patterns in terms of instantaneous vorticity contours visualization, time-trace analysis of drag and lift coefficients and power spectra analysis of lift coefficient are presented and discussed. Drag reduction and suppression of vortex shedding is also discussed in detail and compared with the available experimental and numerical results qualitatively ...