Internal flow field measurement of a single duct-type energy-saving device using the refractive index matching method

Abstract

　One of the energy-saving technologies for ships is a duct-type energy-saving device for the purpose of improving propulsion performance. With the tightening of GHG (Greenhouse Gas) emission regulations, it is necessary to improve the effectiveness of the energy-saving devices. In order to understand the flow field for the purpose of enhancing the effect of the duct type energy-saving device, the flow field around the duct is measured by PIV (Particle Image Velocimetry). However, the measurement is limited to the outside of the duct because the laser sheet does not reach the inside of the duct.

　In this research, we are developing a method to measure the flow field inside the duct by the refractive index matching method using a transparent model close to the refractive index of fresh water. Since we discovered a model material (CYTOP) with a refractive index of 1.34 in the previous research, we measured the flow field in the duct using CYTOP. From the measurement results, it was found that the difference was within 4% compared with the 2-hole Pitot tube and CFD (Computational Fluid Dynamics). Therefore, CYTOP may be used for measuring the flow field inside the duct using the refractive index matching method in fresh water.