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<p>The lateral flow around a rectangular plate under unsteady inflow involves complex fluid dynamic phenomena, including asymmetric flow structures and turbulence-induced instabilities. To investigate these effects, a three-dimensional numerical model combining the Volume of Fluid (VOF) method for gas-liquid two-phase flow and Large Eddy Simulation (LES) was employed to simulate the flow fields around rectangular obstacles with varying opening ratios. The analysis focused on time-averaged and instantaneous flow structures, Reynolds stresses, energy distributions, and modal decomposition of flow fields using Proper Orthogonal Decomposition (POD). Key findings reveal that turbulence intensity in the downstream shear layer escalates with increasing opening ratio <i>E</i>. High-intensity turbulence expanded toward the channel crown when <i>E</i> = 0.5, while a weakening trend was observed at <i>E</i> = 0.9. High-velocity zones extended progressively with larger <i>E</i> values. Upstream flow velocity intensified when the dimensionless pressure differential <i>P</i><sup><i>*</i></sup> exceeded 0.2, amplifying near-obstacle base velocities. Pressure fluctuations and vortex shedding behind the obstacle varied markedly with <i>E</i>. Instantaneous pressure coefficients at <i>E</i> = 0.5 fluctuated between −6 and 2 at 1 times obstacle thickness above the free end, with phase differences reaching 50°. A dominant vortex shedding frequency of 1 Hz across all cases confirmed periodic pressure pulsations. Reynolds normal and shear stresses concentrated in the rear shear layer, intensifying with higher <i>E</i> values. The high Reynolds stress area spreads to the top of the channel at elevated <i>E</i>. The first 20 POD modes captured the flow field’s dominant energy, with the top 5 modes accounting for 34.22% to 88.14% of total energy. Larger <i>E</i> values concentrated energy in lower-order modes, highlighting the growing dominance of large-scale flow structures. These insights provide a theoretical basis for optimizing underwater structures and offshore platforms under unsteady hydrodynamic loads.</p>

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Effects of Opening Ratio on Turbulent Flow Characteristics around a Laterally Fixed Rectangular Obstacle Under Unsteady Inflow

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Xin Guan,
  • Liang Zhong,
  • Jinyang Liu,
  • Haitao Pan,
  • Yuheng Wu,
  • Xingliang Jiang

摘要

The lateral flow around a rectangular plate under unsteady inflow involves complex fluid dynamic phenomena, including asymmetric flow structures and turbulence-induced instabilities. To investigate these effects, a three-dimensional numerical model combining the Volume of Fluid (VOF) method for gas-liquid two-phase flow and Large Eddy Simulation (LES) was employed to simulate the flow fields around rectangular obstacles with varying opening ratios. The analysis focused on time-averaged and instantaneous flow structures, Reynolds stresses, energy distributions, and modal decomposition of flow fields using Proper Orthogonal Decomposition (POD). Key findings reveal that turbulence intensity in the downstream shear layer escalates with increasing opening ratio E. High-intensity turbulence expanded toward the channel crown when E = 0.5, while a weakening trend was observed at E = 0.9. High-velocity zones extended progressively with larger E values. Upstream flow velocity intensified when the dimensionless pressure differential P* exceeded 0.2, amplifying near-obstacle base velocities. Pressure fluctuations and vortex shedding behind the obstacle varied markedly with E. Instantaneous pressure coefficients at E = 0.5 fluctuated between −6 and 2 at 1 times obstacle thickness above the free end, with phase differences reaching 50°. A dominant vortex shedding frequency of 1 Hz across all cases confirmed periodic pressure pulsations. Reynolds normal and shear stresses concentrated in the rear shear layer, intensifying with higher E values. The high Reynolds stress area spreads to the top of the channel at elevated E. The first 20 POD modes captured the flow field’s dominant energy, with the top 5 modes accounting for 34.22% to 88.14% of total energy. Larger E values concentrated energy in lower-order modes, highlighting the growing dominance of large-scale flow structures. These insights provide a theoretical basis for optimizing underwater structures and offshore platforms under unsteady hydrodynamic loads.