Hydrodynamic forcing on a sphere at the bottom of a sloshing tank: experiments and modeling

This study aims to investigate the spatiotemporal variation of hydrodynamic forces around a sphere rigidly fixed to the bottom of a sloshing tank using numerical modeling and physical experiments. Firstly, an experimental study was carried out to generate reliable data for calibrating the numerical model, using a water tank with uniaxial freedom of movement constructed on a monorail operated by a computer-controlled step motor. During the experiments, the tank's movements were recorded using an accelerometer and ultrasonic sensors with a sampling frequency of 200 Hz. The water surface levels during sloshing were recorded with a video camera. The accelerometer and ultrasonic sensor data were used to impose the motion of the sloshing tank into a Reynolds-Averaged Navier-Stokes (RANS)-based numerical model. The video recordings, which comprised temporal fluctuations of the water surface, were used to calibrate the physcial model. Once the first numerical model was calibrated based on water surface level records using image processing methods, the second numerical model was constructed to accommodate a rigid spherical body with a 17 mm diameter connected to the bottom of the sloshing tank. The initial and boundary conditions used in the second numerical model were identical to those used in the physical model to measure the spatiotemporal fluctuations of the surrounding spherical body's kinematic and dynamic variables, respectively. The results demonstrated that sloshing motion substantially influences the boundary layer separation process around the sphere. It was also seen that the stage of the sloshing motion significantly impacts the temporal lag between the variables pressure, velocity and water surface level.