유동가시화 기법을 이용한 평판의 마찰 항력 계측 및 해석

Abstract

Recently, the study on the drag reduction caused by marine coating has been conducted actively through the force measurement technique. In addition to this, flow visualization techniques can be also utilized to investigate the drag reduction effect. Turbulent flow properties on the wall are revealed through measuring its boundary layer by LDV(laser Doppler velocimetry) technique. Instead of the direct measurement of the friction velocity, the difference of the normalized velocity U+ is used to fit it. PIV(particle image velocimetry) technique is also employed to obtain the information on drag coefficient from the wake analysis. Finally, POD(proper orthogonal decomposition) method is used to analyze the velocity fields on the wall, to understand the dominant turbulent flow structures and the possible mechanism of skin friction reduction.n effect. Turbulent flow properties on the wall are revealed through measuring its boundary layer by LDV(laser Doppler velocimetry) technique. Instead of the direct measurement of the friction velocity, the difference of the normalized velocity U+ is used to fit it. PIV(particle image velocimetry) technique is also employed to obtain the information on drag coefficient from the wake analysis. Finally, POD(proper orthogonal decomposition) method is used to analyze the velocity fields on the wall, to understand the dominant turbulent flow structures and the possible mechanism of skin friction reduction.