Simulation Time History and Access Time History Programs (Users Manual)

Abstract : The Simulation Time History Computer Program, STH, has been developed at the Carderock Division of the Naval Surface Warfare Center to provide realistic, random wave time histories of the six-degree-of-freedom (6DOF) ship responses, i.e., surge, sway, heave, roll, pitch, and yaw. The 6DOF origin time histories are developed using transfer functions obtained from the Navy Standard Ship Motion Computer Program, SMP84. The random waves are simulated using a two- parameter Bretschneider wave spectral model. The random waves are represented as either undirectional (longcrested) or spread + or - 90 degrees about a predominant direction (shortcrested). A separate Access Time History Computer Program, ACTH, has been developed to provide additional displacements, velocities, and accelerations at various locations on the ship. Force time histories, which include gravity, are computed in the ship's body axis coordinate system. The ACTH program utilizes the origin time histories generated from the STH program.