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. © 2020, Chongqing Wujiu Periodicals Press. All rights reserved.