Numerical investigation on fluid forces of piggyback circular cylinders in tandem arrangement at low Reynolds numbers  

作　　者：Linfeng Chen Yuhong Dong 

机构地区：[1]School of Naval Architecture and Ocean Engineering,Jiangsu University of Science and Technology,Jiangsu 212003,China [2]Shanghai Institute of Applied Mathematics and Mechanics,School of Mechanics and Engineering Science,and Shanghai Key Laboratory of Mechanics in Energy Engineering,Shanghai University,Shanghai 200072,China

出　　处：《Acta Mechanica Sinica》2021年第4期599-612,I0002,共15页力学学报（英文版）

基　　金：The project was supported by the Natural Science Foundation of Jiangsu Province(Grant SBK2018040999);the Natural Science Research of Jiangsu Higher Education Institutions of China(Grant 18KJB570001);the National Natural Science Foundation of China(Grants 51879123 and 91852111).

摘　　要：Numerical simulations of flows past the piggyback circular cylinders in tandem arrangement are performed by solving the variational multiscale formulation of the incompressible Navier-Stokes equations using in-house finite element method(FEM)codes.The effects of the gap-spacing-to-diameter(G/D)and the two diameter ratio(d/D)on the flow characteristics and the reductions of the root-mean-square(RMS)drag and lift coefficients are considered for Reynolds numbers(Res)are 100 and 200.The validation shows the fluid force coefficients obtained by the in-house FEM codes are in good agreement with the results in the existing literatures.The obtained results show that,with a proper placement of the smaller cylinder(d/D=0.2)behind the larger cylinder,the RMS drag and lift coefficients largely decrease compared to those of the single circular cylinder.When d/D=0.2,the largest reductions of the RMS lift coefficient of the larger cylinder and the RMS total lift coefficient appear at G/D=1.2 as Re=100 and at G/D=1.0 as Re=200.It is observed that the proper placement of the smaller cylinder causes the surrounding vorticity to take opposite sign with the vorticity in the outer region so as to suppress and postpone the vortex shedding in the wake,and that the different positions of the vortex shedding at two Res cause that the largest reductions of the RMS lift coefficient of the larger cylinder and the RMS total lift coefficient appear at different G/D as Re is different.When d/D varies,the variation of the RMS total lift coefficient behaves differently at two Res.It decreases with J/D increasing at Re=100,while it no longer monotonously varies with J/D,but reaches a minimum in the considered range of d/D at Re=200.Moreover,the larger d/D results in stronger suppression and postponement of the vortex shedding in the wake.

关 键 词：Piggyback circular cylinders Hydrodynamic forces Vortex shedding Finite element method Variational multiscale method 

分 类 号：O35[理学—流体力学]