Sung-Bu Suh

Experimental Study on the Eddy Making Damping Effect at the Roll Motion of a Rectangular Barge

This experimental study investigated on the eddy making effect on the roll motion of a rectangular barge in a two-dimensional wave tank. The structure was used to simulate a simplified rectangular barge in the beam sea condition. The structure with a draft one half of its height was hinged at the center of gravity and free to roll by waves. The rectangular barge was tested with regular waves with a range of wave periods that are shorter, equal to, and longer than its roll natural period. Particle image velocimetry (PIV) was employed to obtain the velocity field in the vicinity of the structure. The coupled interactions between the incident wave and the barge were demonstrated by examining the vortical flow fields to elucidate the eddy making effect during the roll motion. For incoming wave with a wave period same as the roll natural period, the barge roll motion was reduced by the eddy making damping effect. At the wave period shorter than the roll natural period, the structure roll motion was slightly reduced by the vertical flow around the barge. However, at the wave period longer than the roll natural period, the eddy making effect due to flow separation at structure corners indeed amplifies the roll motion. This indicates that not only can the eddy making effect damp out the roll motion, it can also increase the roll motion.

Numerical And Experimental Studies On Wing In Ground Effect

Numerical and experimental studies were performed to investigate the aerodynamic performance of a thin wing in close vicinity to the ground. The vortex lattice method (VLM) was utilized to simulate the wing in ground (WIG) effect, which included freely deforming wake elements. The numerical results acquired through the VLM were compared to the experimental results. The experiment entailed varying the ground clearance using the DHMTU (Department of Hydromechanics of the Marine Technical University of Saint Petersburg) wing and the WIG craft model in the wind tunnel. The aero-dynamic influence of the design parameters, such as angles of attack, aspect ratios, taper ratios, and sweep angles were studied and compared between the numerical and experimental results associated with the WIG craft. Both numerical and experimental results suggested that the endplate augments the WIG effect for a small ground clearance. In addition, the vortex lattice method simulated the wake deformation following the wing in the influence of the ground effect.

Numerical Prediction of Ship Motions in Wave using RANS Method

This paper provides the structure of a Reynolds Averaged Navier-Stokes(RANS) based simulation method and its validation results for the ship motion problem. The motion information of the hull computed from the equations of motion is considered in the momentum equations as the relative fluid motions with respect to a non-inertial coordinates system. A finite volume method is used to solve the governing equations, while the free surface is captured by using a two-phase level-set method and the realizable k- model is used for turbulence closure. For the validation of the present numerical approach, the numerical results of the resistance and motion tests for DTMB 5415 at two ship speeds are compared against available experimental data.

A comparative study of constant current control and adaptive control on electrode life time for resistance spot welding of galvanized steels

With using adaptive control of the resistance spot welding machine, the advantage on electrode life time for galvanized steels has been addressed. This study was aimed to evaluate the electrode life time of galvanized steels with applying the constant current control and the adaptive control resistance spot welding process for a comparison purpose. The growth in diameter of electrode face was similar for both the constant current and the adaptive control up to 2000 welds. The button diameter was decreased with weld numbers, however, sudden increase in button diameter with use of the adaptive control after 1500 welds was observed. The peak load was continuously decreased with increasing number of welds for both the constant current and the adaptive control. The current compensation during a weld was observed with using the adaptive control after 1800 welds since the -peak on dynamic resistance curve was detected at later weld time. The current compensation with adaptive control during resistance spot welding enhanced the nugget diameter at the faying interface of steel sheets and improved the penetration to thinner steel sheet.

Numerical Analysis of Free Surface Flow around Blunt Bow Ship Model

*Department of Naval Architecture and Ocean Engineering, Dong-E ui University, Busan, Korea**Marine Transportation Research Department, KORDI Daeduck Branch, Daejon, KoreaKEY WORDS: Blunt bow 뭉뚝한 선수, Computational fluid dynamics (CFD) CFD 전산유체역학, Reynolds averaged navier-stokes (RANS) method RANS기법, Wave breaking 쇄파, Two-phase flow 2상유동, Validation 검증ABSTRACT: This paper presents the numerical results of a simulation of th e free surface flow around a blunt bow ship model and focuses on the validation of the proposed method with a brief investigation of the relation between the resistance and free surface behavior. A finite volume method based on the Reynolds Averaged Navier-Stokes (RANS) approach is used to solve the governing flow equations, where the free sur face, including wave breaking,is captured by using a two-phase Level-Set (LS) m ethod. For turbulence closure, a two equation k-e model with the standard wall function technique is used. Finally, the numerical results are compared with the available experimental data, showing good agr eement.교신저자 박일룡: 부산시 부산진구 엄광로 995, 051-890-2595, irpark@deu.ac.kr

Proposal for Improvement in Prediction of Marine Propeller Performance Using Vortex Lattice Method

Current trends in propeller design have led to the need for extremely complex blade shapes, which place great demands on the accuracy of design and analysis methods. This paper presents a new proposal for improving the prediction of propeller performance with a vortex lattice method using the lifting surface theory. The paper presents a review of the theory and a description of the numerical methods employed. For 8 different propellers, the open water characteristics are calculated and compared with experimental data. The results are in good agreement in the region of a high advanced velocity, but there are differences in the other case. We have corrected the parameters for the trailing wake modeling in this paper, and repeated the calculation. The new calculation results are more in agreement with the experimental data.

An Implementation of Product Data Management System for Design of Ship Propulsion System

Present study introduces an implementation of product data management (PDM) that can be applied to the design of ship propulsion system. The PDM system is developed based on both object oriented software development environment and Open Scene Graph (OSG) library while the system architecture is modeled by the unified modeling language (UML). Suggested PDM system also integrates the modeling & simulation components required to estimate the performance of ship propulsion system as the product information is represented based on the 3-dimensional digital mock-up (DMU). Finally, functions of the implemented PDM system that is integrated with the M&S softwares are illustrated in order to suggest a practical guidance for the efficient design of ship propulsion system.