LAUSR

The hydrodynamics is studied numerically of a horizontal cylinder undergoing forced in-line oscillation beneath the free surface of otherwise quiescent liquid at low Keulegan-Carpenter and Froude numbers. The DFIB-SPH numerical model uniquely combines two well-established techniques: the direct forcing immersed boundary (DFIB) method and smoothed particle hydordynamics (SPH). This facilitates accurate evaluation of the potentially violent free surface motions through SPH and the hydrodynamic force on the solid body using a volume integral. A parameter study is conducted covering a range of Keulegan-Carpenter numbers (KC = 3, 7, and 10) and submergence ratios (H/D = 0.5 − 2.0) at fixed Reynolds number (Re = 100) and Froude number (Fr = 0.35). The flow pattern and transverse force coefficient are found to be affected by the proximity of the cylinder to the free surface. Spectral analysis suggests that free surface wave motions are linked to the transverse force acting on the submerged, oscillating cylinder.