Vortex characteristics and flow-induced forces of the wavy cylinder at a subcritical Reynolds number

Abstract The three-dimensional vortex characteristics behind the wavy cylinders are studied by Large Eddy Simulation (LES) at Re = 3900. The wavelength ratios (λ/Dm = 1.8–5.0) and amplitude ratios (a/Dm = 0.05–0.2) are mainly considered. The spanwise waviness is analyzed for the wavy cylinder on the flow control effect and the results of the unmodified cylinder (UC) are introduced for the comparison. The results show that there is a strong three-dimensional effect in the flow field distribution between the node and the saddle. The phenomenon of the multi-scale and the rib-like vortices are observed in the wake region. Boundary vortex flux of the cylinder reveals the vortex generation mechanism, the conversion of streamwise vortices further explain that mechanism. In addition, the length of vortex formation behind the wavy cylinder is longer than that of the UC. The mean streamwise velocity distribution exhibits a semi-symmetrical U-shaped to V-shaped transformation with the different characteristic positions. With the increment of the amplitude ratio, the statistical average of fluid force coefficients gradually reduces and reaches its minimum value at a/Dm = 0.2. The effect of the flow control is close to that of the UC at λ/Dm = 2.75. Finally, the wake control of the wavy cylinder is mainly related to vortex characteristics.