Large-eddy simulation of a subaqueous cylindrical pendulum*

The motion of pendulums has been long studied. As one of the first pioneers, Galileo Galilei found that the period of a pendulum is constant. This work regards the numerical study of subaqueous pendulums which are not fully understood yet, owing to the formation and, subsequently, dissipation of rich vortical flow structures around the pendulum geometry. Numerical simulations are done using large-eddy simulation (LES) to explore the evolution of the vortical structures and overall flow dynamics of the pendulum motion.

Recently, Mathai et al. (J. Fluid Mech., 2019) reported 2D PIV measurements of cylindrical pendulums in a water tank. We have investigated the 3D flow field around the cylinder by simulating the fluid-structure interaction (FSI) of the pendulums in the context of an immersed boundary model.

We employed the experimental data of Mathai et al. and Mongelli and Battista (Fluids, 2020) to validate our LES results for the angular velocity and the generated torque of the pendulums. The simulation results were used to elucidate the three-dimensional vortex dynamics of the flow around the subaqueous pendulum. Furthermore, we compared the effect of the wake correction proposed by Mathai et al. (2019) on the computed drag forces.