Research on the force mechanism of two tandem cylinders in a stratified strong shear environment

Abstract

A large-eddy simulation of a three-dimensional numerical wave flume is used to study the forces on two tandem cylinders in a stratified strong shear internal wave (IW) environment. By analyzing the pressure distribution and the flow field around two cylinders compared with that of a single cylinder, the mechanism for the influence of the center-to-center (CTC) spacing (L), which is normalized by the cylinder diameter (D), i.e., (L/D), between the two tandem cylinders on the vortex disturbance intensity is explored, further revealing the mechanical response characteristics of the upstream (P1) and downstream (P2) cylinders. The results show that the vortex between two cylinders is the key factor affecting the pressure resistance of the cylinders in the IWs of the depression environment. The vortex disturbance intensity can be distinguished by a normalized critical CTC spacing (Lc/D): when L/D ≤ Lc/D = 2.5, the disturbance is strong, causing P1 and P2 to undergo large forces along and in the opposite direction of the waves, respectively. In addition, the vortex disturbance is more severe in the upper layer than in the lower layer. The correlation between the nondimensional force amplitude (CFn-max) and L/D and that between CFn-max and the nondimensional IW amplitude (ηo/H) is quantified. In the strong disturbance area (L/D ≤ Lc/D), CFn-max has an exponential relationship with (L/D)/(ηo/H) for P1 and is a power function of (L/D)/(ηo/H) for P2.