Flow Visualization and analysis by PIV Measurement System using Micro-bubbles as Tracer in Ship Model Basin-Measurement in Still Water and Regular Waves -
To measure and analyze the flow around ship model, use of micro-babbles as tracer is proposed here. The system has two high speed cameras for stereo photography with continuous laser light sheet. Using continuous laser light sheet flow around ship can be observed directly. To make validation of the present system flow analysis of uniform flow and regular waves in ship model basins is carried out. From the comparison between flow velocity analyzed by the present system and that measured by current meter in different three ship model basins, it is found that the correlation factors of the basins are over 0.99 for flow velocity of ship advance direction. In regular waves the trajectory of the wave motion is compared to small amplitude wave theory and analyzed value. From the comparison it is found that the agreement is well for different wave frequencies. Continuously, flow measurement using a ship model of large tanker has performed in still water and in regular head waves. From the analysis it is found that the difference of the flow vector between still water and regular head waves can be evaluated qualitatively. Thereafter to understand the flow around propeller the tank tests in self propelling condition of the ship model are performed. From the comparison between the tests with propeller and without propeller, the effect of propeller suction is revealed. From the various comparisons the effectiveness of the PIV system using micro-bubbles to obtain flow information around ship is confirmed.
PIV analysis around the Bilge Keel of a Ship Model in Free Roll Decay
The results of an experimental analysis of the velocity field around a ship model in forced roll motion are presented. Tests, carried out at the INSEAN towing tank n° 2, aim to achieve a better physical understanding of the fluid dynamics and a certified experimental data set for CFD validation. Results describe the evolution of the flow field in two cross sections along the bilge keels during damped roll motion. A PIV algorithm based on window deformation is used to improve the estimate of the vorticity. The mean unsteady flow field is obtained by ensemble averaging of time histories. The hydrodynamic damping effectiveness of the bilge keels is highlighted by the generation of strong vortical structures that characterize the transfer of energy between the hull and the surrounding flow field.
A thin circular plate normally and uniformly loaded over a concentric elliptic patch
ABSTRACT This paper is concerned with the small transverse displacement of a thin circular plate elastically restrained along the circular boundary and subject to uniform normal pressure distributed over the area of an ellipse concentric with the plate. The method of complex potentials is used and the general assumptions relating to the small deflexion theory of thin plates are adopted. Explicit formulae for the bending and twisting moments and shearing forces are given at any point on the boundary and at the centre of the plate.