Numerical Analysis of Slip-Length Effects on Fluid–Structure Interaction and Thermal Performance of a Square Cylinder in Turbulent Flow

Articles in Press

Document Type : Full Length Research Article

Authors

1 Department of Mechanical Engineering, Kharazmi University, 15719-14911, Tehran, Iran

2 Department of Mechanical Engineering, Faculty of Engineering, Kharazmi University, Tehran, 15719-14911, Iran

3 School of Mechanical Engineering, Arak University of Technology, 38181-41167, Arak, Iran

Abstract

This study explores how Navier slip boundary conditions, applied either fully or in localized hydrophobic regions, reshape the vortex–induced vibration and heat–transfer behaviour of an elastically mounted square cylinder at a Reynolds number of 22,000 and Prandtl number of the flow is 7. The coupled fluid–structure dynamics are resolved using a finite-volume solver with SST k–ω turbulence modelling and a Runge–Kutta integrator for structural motion. The fluid–structure interaction framework is validated against reference results for both stationary cylinders under slip and no-slip conditions and conventional flow-induced vibration (FIV) responses, showing excellent agreement. Simulations are performed over the reduced-velocity range of 3–14 and various slip lengths (0\le b*\le0.2). For fully hydrophobic surfaces, the cross-flow vibration amplitude is substantially reduced—by nearly 50% at Ur=10—while the inline oscillation amplitude grows markedly, reaching almost a twofold increase at Ur=12. These changes coincide with an elevation in shedding frequency and a notable weakening of lift fluctuations. Heat transfer is consistently strengthened under slip, and the mean Nusselt number reaches a maximum enhancement of approximately 53% at higher reduced velocities. When slip is introduced only on selected surfaces, its effect becomes strongly configuration-dependent. Rear-face hydrophobicity produces the greatest suppression of transverse motion, front-face slip yields the most pronounced reduction in force coefficients, and only full-surface slip results in a significant rise in heat-transfer performance. Despite local irregularities with reduced velocity, the overarching trends remain clear, with slip accelerating vortex shedding, moderating cross-flow vibrations, increasing streamwise oscillations, and enhancing convective transport. These findings demonstrate that the strategic distribution of hydrophobic regions can serve as an effective passive-control approach for improving both the dynamic and thermal behavior of square cylinders in turbulent flow.

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Journal of Heat and Mass Transfer Research

Articles in Press, Accepted Manuscript
Available Online from 13 April 2026

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History

  • Receive Date: 11 December 2025
  • Revise Date: 29 March 2026
  • Accept Date: 13 April 2026

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