Numerical simulation of two-dimensional backward-facing step flow using OpenFOAM
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摘要:
为提升不可压缩流动中湍流模拟精度并发展高效湍流模型，本研究在先前提出的 partial averaged fluctuation velocity （PAFV） 湍流模型的基础上进行了部分改进，通过引入侧偏脉动速度调整动力黏度，构建了一款相等于无人工系数的主要用于不可压缩流体计算的湍流模型，以优化近壁面边界层分离的预测能力。基于 OpenFOAM 开源平台开发了模型求解器模块，对二维后向台阶流动进行了高分辨率数值模拟，获取瞬时速度场与脉动速度分布以及雷诺应力分布数据。结果表明：与 Spalart-Allmaras（S-A）、
k-ω SST 两种常用湍流模型相比，PAFV 模型结果与理论值在部分区域的符合度更好，由于引入了侧偏脉动速度并降低了动力黏度，该新湍流模型在捕捉台阶下游近区的漩涡时表现出更高的敏感性，对漩涡的捕捉能力更强，可准确预测湍流边界层分离过程。然而，在捕捉上壁旋涡区方面，该模型表现不及传统湍流模型，且对远场涡结构的预测存在滞后，其有待进一步优化。本研究为近壁流动优化提供新思路，未来将致力于提升模型普适性。-
关键词:
- OpenFOAM软件 /
- 后向台阶流动 /
- PAFV湍流模型 /
- 边界层分离 /
- 不可压缩流动
Abstract:To enhance the accuracy of turbulence modeling in incompressible flows and to develop efficient turbulence models, this study builds upon the previously proposed Partial Averaged Fluctuation Velocity （PAFV） turbulence model and introduces several improvements. By incorporating lateral fluctuation velocity to adjust the viscosity coefficient, a turbulence model was developed that is essentially free of empirical constants and primarily applicable to incompressible flow computations, with improved capability in predicting near-wall boundary layer separation. The model solver was implemented on the open-source platform OpenFOAM, and high-resolution numerical simulations were conducted for two-dimensional backward-facing step flows to obtain instantaneous velocity fields, fluctuation velocity distributions, and Reynolds stress data. The results demonstrate that, compared with the commonly used Spalart–Allmaras （S-A） and k–ω SST turbulence models, the PAFV model exhibits better agreement with theoretical values in certain regions. Due to the introduction of lateral fluctuation velocity and the reduction of viscosity, the new turbulence model shows enhanced sensitivity in capturing vortices in the near-wake region downstream of the step, thereby providing stronger capability in vortex prediction and more accurate characterization of turbulent boundary layer separation. However, in terms of capturing the upper-wall vortex region, this model performs worse than traditional turbulence models, and there is a lag in predicting the far-field vortex structure, which needs further optimization. This study provides new ideas for near-wall flow optimization, and future work will be dedicated to improving the universality of the model.
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图 3 Re=389时台阶下游流场的时均流速场分布
Figure 3. Time-averaged velocity field distribution of the downstream flow field of the step at Re=389
图 4 后向台阶流动中平均流场结构的区域划分
Figure 4. Regional division of the average flow field structure in backward-facing step flow
图 5 Re=
1000 时台阶下游流场的时均流速场分布Figure 5. Time-averaged velocity field distribution of the downstream flow field of the step at Re=
1000 
图 6 Re=
2260 时台阶下游流场的时均流速场分布Figure 6. Time-averaged velocity field distribution downstream of the step at Re =
2260 
图 7 不同湍流模型在不同位置X/L上速度变化曲线（Re=389）
Figure 7. Velocity variation curves of different turbulence models at different positions X/L （Re=389）
图 8 不同湍流模型在不同位置X/L上速度变化曲线（Re=
1000 ）Figure 8. Velocity Variation Curves of Different Turbulence Models at Different Positions X/L （Re=
1000 ）
图 9 不同湍流模型在不同位置X/L上速度变化曲线（Re=
2260 ）Figure 9. Velocity variation curves of different turbulence models at different positions X/L （Re=
2260 ）
图 10 Re=389时台阶下游流场的瞬时脉动速度场分布
Figure 10. Instantaneous fluctuating velocity field distribution of the downstream flow field of the step at Re=389
图 11 Re=
1000 时台阶下游流场的瞬时脉动速度场分布Figure 11. Instantaneous fluctuating velocity field distribution of the downstream flow field of the step at Re=
1000 -
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