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.
Towing tank PIV measurement system, data and uncertainty assessment for DTMB Model 5512
Abstract A towed PIV system designed by DANTEC Measurement Technology for the Iowa Institute of Hydraulic Research towing tank is commissioned by measuring the mean velocity and Reynolds stresses at the nominal-wake plane of a model-scale ship. The mean velocities are compared with previous 5-hole pitot probe data. Uncertainty assessment following standard procedures is used to quantify the comparisons and reach conclusions regarding the quality of the data. The PIV results are analyzed with regard to axial velocity defects, axial vorticity, and level, pattern and anisotropy of turbulence. Quantitative comparisons with 5-hole pitot data shows that PIV uncertainties are about 1% lower than those for 5-hole pitot. However, data differences are larger than RSS of PIV and 5-hole pitot uncertainties for the axial and vertical velocity components, indicating unaccounted for bias and precision limits. The bias error of the pitot probe in a shear flow is discussed, and a method for reducing the bias error is suggested. The data is being used for verification and validation of RANS simulation of DTMB Model 5512.
Points of strong summability of Fourier series
In this paper we present a new solution of Hardy and Littlewood's problem concerning strong summability of Fourier series; we also present a property of points of strong summability.