Three dimensional wake survey behind a ship model using hot-film anemometers

摘要

This thesis presents results of investigative experiments using constant temperature anemometry to measure three dimensional flows in a towing tank. A three dimensional probe was configured from three single 45° hot-film probes mounted with their sensor plane at 120° to each other. Presented are the calibration data for each of the single sensors for variations in velocity, yaw and pitch angles as well as the performance of the three probes when mounted in close proximity to each other. The calibration data of each sensor was fitted by a two parameter non-linear polynomial in velocity and yaw angle. The probes were insensitive to variations in angle of pitch. A nominal wake survey was done with the three dimensional probe on the Institute of Marine Dynamics ship model No. M445, the model of a modern fishing vessel form. The results from this wake survey are compared with the results from an existing pitot tube wake survey done for this model. The spectrum of turbulence in the wake is presented.