通过研究泥沙颗粒的沉降速率和沉降规律,可以有效预测和控制水体淤积和沉积过程,阻力系数Cd是预测沉速的核心参数。针对非球形泥沙颗粒沉速预测中缺乏普适性、精度高公式的问题,系统对比了8个具有代表性的阻力系数公式在不同雷诺数区间...通过研究泥沙颗粒的沉降速率和沉降规律,可以有效预测和控制水体淤积和沉积过程,阻力系数Cd是预测沉速的核心参数。针对非球形泥沙颗粒沉速预测中缺乏普适性、精度高公式的问题,系统对比了8个具有代表性的阻力系数公式在不同雷诺数区间的预测性能。基于统一筛选的独立数据集,采用预测值-实测值图与平均相对误差相结合的方法,评估各公式的精度。研究结果表明:在极低雷诺数区间(10-4<Re<0.1),Cheng公式表现最优;在过渡区与紊流区(0.1<Re<10^(4)),Haider公式综合精度最高、稳定性最好;Madhav and Chhabra公式(0.1<Re<1)与Swamee公式(1<Re<200)可作为提升精度的补充或替代选择。在现有8个非球形泥沙颗粒沉速及阻力系数计算公式范围内提供分区间推荐序列,未涵盖最新机器学习模型,后续可作为传统经验公式与智能算法融合研究基础。展开更多
In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbu...In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.展开更多
文摘通过研究泥沙颗粒的沉降速率和沉降规律,可以有效预测和控制水体淤积和沉积过程,阻力系数Cd是预测沉速的核心参数。针对非球形泥沙颗粒沉速预测中缺乏普适性、精度高公式的问题,系统对比了8个具有代表性的阻力系数公式在不同雷诺数区间的预测性能。基于统一筛选的独立数据集,采用预测值-实测值图与平均相对误差相结合的方法,评估各公式的精度。研究结果表明:在极低雷诺数区间(10-4<Re<0.1),Cheng公式表现最优;在过渡区与紊流区(0.1<Re<10^(4)),Haider公式综合精度最高、稳定性最好;Madhav and Chhabra公式(0.1<Re<1)与Swamee公式(1<Re<200)可作为提升精度的补充或替代选择。在现有8个非球形泥沙颗粒沉速及阻力系数计算公式范围内提供分区间推荐序列,未涵盖最新机器学习模型,后续可作为传统经验公式与智能算法融合研究基础。
基金supported by the National Natural Science Foundation of China(Grant Nos.12388101 and 12472221)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-oy10).
文摘In sediment transport on a mobile erodible bed,near-bed particles tend to preferentially locate under specific flow regions and form an uneven bedform.These moving and mobile particles can significantly modulate turbulence at various scales,from inertial large-scale motions to small viscous motions.This study analyzes the particle-resolved direct numerical simulation data of particle-laden two-phase flow with multilayers of particles in turbulent flows over static and mobile beds.The double-average method is adopted for energy transfer analysis.The result shows that the alternative streaky bedform in the spanwise directions correlates with the streak structures in the near-wall turbulence in the mobile bed case.The energy redistribution and exchange,as well as the dissipation,are analyzed in detail,and an energy transfer diagram is given in the last to summarize the energy transfer processes.In both the static and mobile bed cases,flow energy is introduced into the system via the work performed by volume forces acting on the mean flow.The viscous dissipations in the double mean and form-induced fields are more pronounced in the static bed case,and the work done by the fluid-particle interfacial stress in the double mean and turbulent fields is more pronounced in the mobile bed case.The prominent energy contribution in the form-induced field is the production by the form-induced stress on the mean strain in the mobile bed case.In addition,sediment transport involving a limited number of mobile particles is insufficient to capture the energy transfer processes that occur over the troughs and may intertwine the energy transfer processes over the mobile particles and the fixed particle bed.
