Fluid memory effects on the trajectory of a submersible

Current mathematical models are based upon the assumption that the flow of the fluid around a manoeuvring vessel is quasi-steady. This assumption can be eliminated by incorporating the time history of the motion in the model. Impulse response functions for a submersible are calculated and used to determine the effect of introducing time history phenomena into the linear equations describing the sway and yaw motions in response to rudder movements. These effects are shown to be very small.