• Journal of the Society of Naval Architects of Korea
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• v.32 no.2
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• pp.43-55
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• 1995

The turbulent flow around the strut mounted on the plate is studied numerically. The main objective of this paper is to validate the numerical scheme by the comparison of the computed results with the measured one, especially, to investigate the applicability of the Baldwin-Lomax(B-L) model to the juncture flow. Computations are made by solving Reynolds-averaged wavier-Stokes equation with MAC method. The computed results are compared with experimental data of Dickinson, collected in the wind tunnel at DTRC. Comparisons show good agreements generally except at the region of wake and very near the juncture. Reynolds stress model seems to be required to improve the accuracy applicable to the juncture flow in spite of the many simplification of the turbulence modelling in B-L model.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.87-89
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• 2000

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.81-83
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• 2000

• Proceedings of the KWS Conference
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• 1996.05a
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• pp.149-153
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• 1996

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.252-261
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• 2024

This research establishes design standards for vortex reduction devices (VRDs) aimed at minimizing underwater radiated noise by mitigating horseshoe vortex (HSV) and root vortex (RV) generated at the junction of appendages and the hull of underwater vehicles. Initial analysis replaced the influence of appendage dimensions and flow velocity with the Reynolds number by verifying the Reynolds similarity of vortex flows. The three-dimensional surfaces of VRDs were parameterized using Bezier curves. Optimal length-to-height ratios were identified by evaluating the vortex reduction performances of VRDs with various dimensions. Ultimately, non-dimensional design standards were derived for VRDs, ensuring effective vortex reduction across any appendage, thereby enhancing stealth performance.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.26-35
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• 1997

본 연구에서는 GTAW 및 GMAW 공정에서 용접부의 열 및 물질유동해석을 수행하기 위한 지배방정식, 해석방법 및 절차를 제시하였으며, 또 실제로 해석한 결과를 에제로 살펴보았다. 그러나 용접공정은 매우 복잡한 물리적 현상을 야기하기 때문에 용접부 수치해석 모델 설정 및 해석의 수행은 용이한 일은 아니다. 그렇지만 이 분야의 연구는 용접 구조물에 대해서 사전에 용접조건 설정을 위한 실제 용접 작업 수행을 하지 않고 용접부 형상, 결함, 냉각속도, 응고 등의 예측을 위한 매우 효과적이고 경제적인 방법으로 사료되기 때문에 용접 분야에 종사하는 관련 연구자들의 관심이 한층 더 요망된다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.114-121
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• 1997

회전 열파이프의 열전달 성능은 액막 두께 및 증발부로 귀환되는 응축 액막 유동율에 의해 결정된다. 그 동안 응축액 유동율을 촉진시키기 위하여 용기 내벽에 groove, 테이퍼 및 나선형 코일을 삽입하여 유동율을 높이는 방법들이 연구되었다. 본 연구도 회전 열파이프의 내부 관벽 구조에 관한 것으로써 삼각 단면을 갖는 회전 열파이프의 열전달 특성을 파악하고자 하였다. 삼각 단면을 갖는 회전 열파이프는 고속 회전 영역에서 모서리 부분으로 액막이 집중되어 관 내벽에 형성되는 액막 두께를 줄일 수 있으나 증발부에서 국부적인 과열이 발생되어 불안정한 작동 상태를 나타내었다. 따라서 본 연구에서는 개선방안으로 증발부에 부분적으로 원형관을 접합하였으며, 그 결과 dry-out의 억제와 함께 삼각 유동 단면에 의한 액막 두께 감소 효과를 볼 수 있었다. 회전체 발열부 냉각에 적용시키기 위해서는 앞으로 최적의 기하학적 형상에 따른 충전율 및 액막에서의 열전달에 대한 정량적인 해석 연구가 필요할 것으로 생각된다.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.24-40
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• 1997

Horseshoe vortices generated around the juncture between the ship and her appendages often lower a performance of the ship by increasing the appendage drag and making a non-uniform wake on the propeller plane. This paper investigates numerically how the fillet around the juncture of the leading edge influences the juncture flow and the appendage drag. Computation has been made by solving Navier-Stokes equations with MAC method and the flows are at the Reynolds number of 5,000. Five fillets with different height-breath ratios and curvatures are chosen as test models to find out the effects of the shape of fillets on the appendage drag and wake. Computational results show that fillets with a smaller height-breath ratio and/or with a concave curvature has smaller appendage drag and more uniform wake.

• Journal of Welding and Joining
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• v.29 no.2
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• pp.4-6
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• 2011

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.43-49
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• 2019

In this study, a new approach using graphene oxide (GO) powder-composited Sn-3.0Ag-0.5Cu(in wt.%) solder paste for improving the bending reliability of solder joints between a flexible substrate and small outline package (SOP) was suggested. The GO addition slightly affected the melting temperature, however, the change in the melting temperature was not significant. Meanwhile, we observed the addition of GO could suppress IMC growth and IMC thickness of solder joint during the reflow process. Moreover, the cyclic bending test was also performed for evaluation of reliability in solder joint and we could improve the cyclic bending reliability of solder joint by adding GO powders. For 0.2 wt.% of GO added to the solder joint, the bending lifetime was increased to 20% greater than that without GO. Pull strength and ductility of the solder joint with GO were also higher than those of the joint without GO and it was assumed that this effect by adding GO could contribute to improve cyclic bending reliability of solder joint.