多点TV撮影による流速測定法に関する研究

第2報実船伴流分布の計測

抄録

A new velocity measurement method was applied for the fullscale ship wake measurement. The wake distribution was measured on a 105 m long 5, 800 displacement ton training ship “SEIUN-MARU”. The 3-dimensional velocities of tracers were measured from the synchronized screen images of 3 CCD TV cameras which were installed on the hull surface. The 3-dimensional velocity distributions, i. e. wake distributions, were then calculated at the sections near the ship stern by interpolating the measured tracer velocities.
The measurements were made twice. One was in the condition of a conventional propeller equipped and the other was in the condition of a highly skewed propeller equipped. In the first experiment, a LDV measurement was also performed by another research group. Therefore, the authors could compare their results with the simultaneously measured LDV results besides the comparison between the different propeller conditions. The following results were obtained :
(1) The present measurement result is very reasonable and agrees fairly well with the LDV result. It can be said that the present method is simpler and less expensive than the LDV method. This system is also less sensitive to the hull vibration. In addition, the present system can measure the 3-dimensional velocity distribution in the measurement volume.
(2) The secondary flow distributions clearly show the development of the bilge vortex.
(3) The wake distribution in the case of the highly skewed propeller is similar to that of the conventional propeller case. However, the wake fraction is about 0.1 lower in the highly skewed propeller case than that in the conventional propeller case.