TY - JOUR

T1 - Flow around a surface-mounted finite circular cylinder completely submerged within the bottom boundary layer

AU - Zhang, Di

AU - Cheng, Liang

AU - An, Hongwei

AU - Draper, Scott

PY - 2021/3/1

Y1 - 2021/3/1

N2 - This paper presents a detailed investigation on the flow characteristics and the bed-shear-stress distribution around a finite circular cylinder at a fixed Reynolds number (Re = 2 ×104) and seven aspect ratios (AR = 0.5∼6) by solving the Reynolds Averaged Navier–Stokes (RANS) equations. It is found that, for a moderate Reynolds number and a relatively large boundary-layer thickness, the time-averaged streamwise vortex structure will be transformed from the ‘Dipole Type’ at AR≤3 to the ‘Three-Pairs Type’ at AR≥4. It is the first time that the ‘Three-Pairs Type’ vortex structure has been reported, which consists of Time-Mean Streamwise Tip Vortices, Time-Mean Streamwise Base Vortices and Time-Mean Streamwise Bottom Vortices. Besides, this study indicates that, with increasing AR, the maximum time-averaged bed-shear-stress amplification magnitude upstream of the cylinder will first decrease and then increase, with the minimum occurring at approximately AR = 3.0, due to the influence of AR on the horseshoe vortices. Additionally, this study manifests that different critical AR values can be obtained for various flow variables. For instance, in terms of the total lift coefficient of the cylinder and the transverse fluctuating velocity in the symmetry plane at the mid-height of the cylinder, the critical AR is equal to ARc=3.0 and ARc=2.0, respectively.

AB - This paper presents a detailed investigation on the flow characteristics and the bed-shear-stress distribution around a finite circular cylinder at a fixed Reynolds number (Re = 2 ×104) and seven aspect ratios (AR = 0.5∼6) by solving the Reynolds Averaged Navier–Stokes (RANS) equations. It is found that, for a moderate Reynolds number and a relatively large boundary-layer thickness, the time-averaged streamwise vortex structure will be transformed from the ‘Dipole Type’ at AR≤3 to the ‘Three-Pairs Type’ at AR≥4. It is the first time that the ‘Three-Pairs Type’ vortex structure has been reported, which consists of Time-Mean Streamwise Tip Vortices, Time-Mean Streamwise Base Vortices and Time-Mean Streamwise Bottom Vortices. Besides, this study indicates that, with increasing AR, the maximum time-averaged bed-shear-stress amplification magnitude upstream of the cylinder will first decrease and then increase, with the minimum occurring at approximately AR = 3.0, due to the influence of AR on the horseshoe vortices. Additionally, this study manifests that different critical AR values can be obtained for various flow variables. For instance, in terms of the total lift coefficient of the cylinder and the transverse fluctuating velocity in the symmetry plane at the mid-height of the cylinder, the critical AR is equal to ARc=3.0 and ARc=2.0, respectively.

UR - http://www.scopus.com/inward/record.url?scp=85098681658&partnerID=8YFLogxK

U2 - 10.1016/j.euromechflu.2020.11.011

DO - 10.1016/j.euromechflu.2020.11.011

M3 - Article

AN - SCOPUS:85098681658

VL - 86

SP - 169

EP - 197

JO - European Journal of Mechanics B-Fluids

JF - European Journal of Mechanics B-Fluids

SN - 0997-7546

ER -