Triple coordinate transforms for prediction of falling cylinder through the water column

Triple coordinate systems are introduced to predict translation and orientation of falling rigid cylinder through the water column: earth-fixed coordinate (E-coordinate), cylinders main-axis following coordinate (M-coordinote), and hydrodynamic force following coordinate (F-coordinate). Use of the triple coordinate systems and the transforms among them leads to the simplification of the dynamical system. The body and buoyancy forces and their moments are easily calculated using the E-coordinate system. The hydrodynamic forces (such as the drag and lift forces) and their moments are easily computed using the F-coordinate. The cylinders moments of gyration are simply represented using the M-coordinate. Data collected from a cylinder-drop experiment at the Naval Postgraduate School swimming pool in June 2001 show great potential of using the triple coordinate transforms.