Hydrodynamic Damping of an In-Line Oscillating Cylinder in Steady Flow

This study conducts a series of analysis to reconstruct the time-dependent in-line forces on an in-line oscillating cylinder in steady flow. The analysis involves reconstructing these forces from several approaches and comparing them with those obtained from the three-dimensional numerical simulations conducted at a fixed Reynolds number of 500 based on the incoming steady flow velocity. A range of velocity ratio r* (cylinder-oscillation-velocity to current velocity) from 0.1 to 1.83 at amplitude-to-diameter ratio A* = 1/\pi are considered. To quantify their performance, the reconstructed in-line force and damping force from the conventional Morison Equation (MOJS) with the relative and independent velocity models are examined. The results show that the independent velocity model outperforms the relative velocity model and provides a good fit at large r* where the wake is controlled by the cylinder oscillation. The study also demonstrates that the independent velocity model using a more general form of MOJS is superior to the conventional formula in predicting the in-line force. Recommendations are provided on selecting velocity models in force estimation at different r* ranges.