Sangbong Lee

Computational Prediction of Speed Performance for a Ship with Vortex Generators

Abstract The computational prediction method of speed performance for a ship with vortex generators is proposed. The Reynolds averaged Navier-Stokes equation has been solved together with the application of Reynolds stress turbulence mod el. The computations are carried out under identical conditions of the experimental method, i.e., towing and self-propulsion calculations without and with vortex generators. The speed performance in full scale is obtained through analyzing the computational results in model scale according to the revised model-ship performance analysis method of ITTC’78 with considering the vortex generators into account. The characteristics of resistan ce, self-propulsion and wake characteristics on the propeller plane are investigated. The proposed computational prediction clearly shows the effect of vortex generators and can be applicable to the design tool for vortex generators. ※Keywords: Vortex generator(와류생성기), Speed performance(속도성능), Computational prediction(수치적 추정), Revised ITTC’78 analysis method(수정된 ITTC’78 해석법), Resistance(저항), Self-propulsion(자항), Wake characteristics(반류특성)

2D WPS System for Measuring the Location Changes in Real Time of PAL-XFEL Devices

Several parts that comprise the large scientific equipment should be installed and operated at precise three-dimensional location coordinates X, Y, and Z through survey and alignment to ensure their optimal performance. As time goes by, however, the ground uplifts and subsides, which changes the coordinates of the installed components and leads to alignment errors ΔX, ΔY, and ΔZ. As a result, the system parameters change, and the performance of the large scientific equipment deteriorates accordingly. Measuring the change in the locations of the systems comprising the large scientific equipment in real time would make it possible to predict alignment errors, locate any region with greater changes, realign components in the fast changing region and shorten the time of survey and alignment. For this purpose, a hydrostatic leveling sensor (HLS) with 0.2 μm resolution was installed and is operated in the PAL-XFEL building. In addition, a 2D wire position sensor (WPS) with a 0.1 μm resolution was installed and is operated in the undulator sections where measurements of the two-dimensional changes of the systems (vertical & horizontal) are necessary. This paper is designed to introduce the operating principle of the 2D WPS, the installation and operation of the WPS system, and the way in which the WPS system is utilized in order to ensure beam stability.