Prediction of Falling Cylinder Through Air-Water-Sediment Columns

Abstract

A falling rigid body through air, water, and sediment is investigated experimentally and theoretically. Two experiments were conducted to drop rigid cylinders with density ratio around 1.8 into shallow water (around 13 m deep) in the Monterey Bay (Exp-1) and into the Naval Postgraduate School’s swimming pool (Exp-2). During the experiments, we carefully observe cylinder track and burial depth while simultaneously taking gravity cores (in Exp-1). After analyzing the gravity cores, we obtain the bottom sediment density and shear strength profiles. The theoretical work includes the development of a 3D rigid body impact burial prediction model (IMPACT35) that contains three components: triple coordinate transform and hydrodynamics of a falling rigid object in a single medium (air, water, or sediment) and in multiple media (air-water and water-sediment interfaces). The model predicts the rigid body’s trajectory in the water column and burial depth and orientation in the sediment. The experimental data (burial depth, sediment density, and shear strength) show the capability of IMPACT35 in predicting the cylinder’s trajectory and orientation in a water column and burial depth and orientation in sediment.