横向间断肋条湍流减阻大涡模拟分析

目的 通过改变肋条结构，提高传统肋条的减阻效果。方法 基于Walsh肋条减阻实验，利用LES理论的WALE模型以及PISO算法，对传统连续肋条及新型间断肋条进行了仿真模拟计算，其中梯度求解基于Green-Gauss节点格式，压力求解采用二阶格式，动量方程求解采用中心差分格式，时间离散采用二阶隐式格式。通过对比分析两种不同肋条结构流场湍流流动的细节及肋条的减阻率，探究新型肋条结构的减阻作用和机理。结果 LES方法准确地再现了Wlash实验的流场细节及计算结果，相同计算条件下，传统连续肋条表面摩擦减阻率和黏性减阻率均为4.641%，而新型间断肋条表面摩擦减阻与黏性减阻率高达9.317%和6.306%。结论 新型间断肋条相较于传统连续肋条的表面摩擦减阻率和黏性减阻率皆得到了较大的提升。新型间断肋条具有较高的减阻率是由于横向肋条阻断作用使得大涡旋受到抑制而分裂成较小的涡旋，降低了近壁面流体的流速，减弱了湍流扰动对流体的影响，使低速流体更加稳定的发展。

Large Eddy Simulation Analysis of Turbulent Drag Reduction for Transverse Discontinuous Ribs

The work aims to improve the drag reduction effect of traditional ribs by changing the rib structure. Based on the Walsh rib drag reduction experiment, the WALE model of LES theory and the PISO algorithm were used to simulate and calculate the traditional continuous ribs and new discontinuous ribs. The gradient solution was based on the Green-Gauss node format, the pressure solution adopted a second-order format, the momentum equation was solved with a central difference format, and the time dispersion used a second-order implicit format. By comparing and analyzing the details of the turbulent flow in the flow field of two different rib structures and the drag reduction rate of the ribs, the drag reduction effect and mechanism of the new rib structure were explored. LES method accurately reproduced the flow field details and calculation results of the Wlash experiment. Under the same calculation conditions, the surface friction reduction rate and viscosity reduction rate of traditional continuous ribs were both 4.641%, while the frictional drag reduction and viscous drag reduction rate of new discontinuous ribs were as high as 9.317% and 6.306%. Compared with the traditional continuous ribs, the new discontinuous ribs have greatly improved the surface friction reduction rate and the viscosity reduction rate. The new discontinuous ribs have a higher drag reduction rate due to the lateral rib blocking effect, which causes the large vortex to be suppressed and split into smaller vortices, thus reducing the flow velocity of the near-wall fluid and weakening the influence of turbulent disturbance on the fluid to make low-speed fluids develop more stably.