Escort tugs use the combination of yaw angle and azimuthing thrusters to generate the hydrodynamic forces that are used to control a disabled tanker. The yaw angles used for escort operations are considered to be "off-design" conditions in normal naval architecture and the resulting flow patterns at these yaw angles have not been studied in detail. Particle Image Velocimetry (PIV) is an important measurement technique for fluids research. A laser light sheet is used to illuminate the fluid in the region where measurements are to be made. The flow through the measurement area is seeded with small particles, and photographs are taken at successive intervals. By timing the intervals to ensure that the same particles are in each exposure, vectors of flow within the measurement space can be calculated, once the measurement space has been calibrated. In its simplest form, the technique is applied in two dimensions with a single camera, but by using stereo photography, it can be extended to three dimensions. The biggest advantage of PIV is its ability to determine fluid velocity simultaneously throughout the measurement space.
National Research Council of Canada. Institute for Ocean Technology
St. John's, Newfoundland, Canada
Technical Report (National Research Council of Canada. Institute for Ocean Technology), no. TR-2005-10 (2005).