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RISS 인기검색어
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- 저자 : 승삼선(Samsun Seung) (검색결과 5 건)
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승삼선(Samsun Seung),이재성(Jaesung Lee),김상일(Sangil Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-
This experimental study is investigated the wake flow around a elastically supported circular cylinder. In this study, the Reynolds Numbers are varied in the region of 1.4×10<SUP>4</SUP>≤Re≤3.2×10<SUP>4</SUP>. Under these conditions we have figured out the process of wake mechanism and moving path of the vortex by measuring the velocity at each position in the wake around a cylinder. Also these facts from wind tunnel test are proved by flow visualization test through water channel. As a result, we have concluded as followings : i) The process(formation→growth→collapse) of vortex in the wake around a cylinder is observed, ii) The vortex efflux angle is about 16~17 degrees under the experimental conditions. These degrees have no concern with velocity change and the existence of flow-induced vibration of a cylinder. iii) The moving path of vortex center is inferred by spectrum analysis of fluctuating velocity behind the cylinder. These are confirmed by doing visualization test.
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회전하는 하나의 내부 원통에서 서로 다른 반경비가 Taylor-Couette 유동에 미치는 영향
승삼선(Samsun Seung),김상일(Sangil Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.12
회전하는 하나의 내부 원통이 서로 다른 반경비를 갖는 경우에 Taylor vortex형성에 미치는 영향에 대해 수치해석을 수행하였다. 서로 다른 반경비는 내부 원통 중앙을 기준으로 동일한 폭에 깊이를 달리한 것으로 먼저 반경비가 0.83인 매끈한 내부 원통에 대한 수치계산 결과를 기존의 실험결과와 비교하여, 타당성을 검토하였다. 그런 다음, 내부 원통 중앙에 동일한 홈의 폭에 깊이를 각각 3, 6, 9, 12 mm 달리한 내부 원통에 회전수 25, 100 rpm인 경우의 수치계산 결과와 비교하였다. 그 결과, Taylor vortex는 층류인 경우 내부 원통 양끝에서 생성되기 시작하지만 홈이 있는 경우에는 홈 모서리에서도 이루어짐을 확인하였다. 홈의 깊이와 내부 원통의 회전수에 따라 쌍으로 이루어진 Taylor vortex셀의 폭이 달라졌으며, 회전수가 큰 경우에는 작은 경우보다 Taylor vortex 셀의 폭이 넓어져 개수가 감소하였다. 또한 각각의 Taylor vortex 쌍의 vortex 중심은 이웃하고 있는 vortex 쌍 사이의 vortex 중심보다 더 가깝게 자리하고 있음을 확인하였다. The Taylor-Couette flow in a rotating inner cylinder with different radius ratios has been studied numerically to show the effects of Taylor vortices formation, where different radius ratios refer to the varied depths having the same width based on the center of the inner cylinder. The numerical calculations results are compared with those of the straight inner cylinder. In order to examine the feasibility of the numerical calculations, the numerical results are compared with existing experimental results for a straight inner cylinder. Then, we compare the numerical results in the case of inner cylinders with different radius ratios. Initially, laminar Taylor vortices form at the end walls and corners of the groove. Results show that the widths of pairs of Taylor vortex cells are varied according to the depth and rotational speed of the inner cylinder. In the case involving a higher rotational speed of inner cylinder widths, and the number of pairs of Taylor vortex cells are wide and decreasing than low rotational speed of it. In addition, the vortex centers of each Taylor vortex pair are closer together than the vortex centers between neighboring vortex pairs.
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상류에 있는 물체의 직경변화에 따라 후류 물체가 받는 영향
김진남(Jinnam Kim),승삼선(Samsun Seung),김상일(Sangil Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5
This experimental study is carried out the impacts of a downstream cylinder in the wake change on upstream objects diameter. The V-shaped object is located in the upstream of the test section and the circular cylinder included load-cell is located in the downstream. We investigated the velocity distribution of the wake emitted from the upstream object with changing its diameter. Also the fluctuating lift coefficient and Karman-vortex emission frequency are investigated with changing position of downstream cylinder. They are concluded as followings: i) the flow velocity in the wake is smaller than main stream, ii) the lock-in phenomenon is occurred when the upstream objects diameter is bigger than downstream cylinders one, iii) in order to be maximum fluctuating lift force of the downstream cylinder in the wake, the position of the downstream cylinder must be moved with changing diameter of the upstream object together.
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서로 다른 두 개의 와류방출 주파수간의 조화형 비선형 간섭
김상일(Sangil Kim),승삼선(Samsun Sueng),이승철(Seung-Chul Lee),김효준(Hyojun Kim) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5
This study is on the nonlinear interaction between two different vortex shedding frequencies from the cylinder having two diameters. In particular, two different vortex shedding frequencies are made by making the cylinder having two diameters artificially. And the flow velocity fluctuations behind the cylinder are measured three dimensionally. Also, we made a hole of pressure transducer for measuring the pressure on the cylinder surface and measured the pressure of cylinder surface. The pressure signal from the pressure transducer is used as basic signal. The TSC is used for checking the strength of nonlinear interaction between two different vortex shedding frequencies. As a result, it is clarified that; I) frequency distribution behind the cylinder. ii) three dimensional flow state behind the cylinder by calculation of ensemble average. iii) a close connection between the vertical vortex and change of low frequency by nonlinear interaction between two different vortex shedding frequencies from the cylinder having two diameters.
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이재성(Jaesung Lee),김상일(Sangil Kim),승삼선(Samsun Seung) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.11
본 연구는 탄성지지된 단독원기둥의 후류에 관한 실험적연구이다. 본 실험은 1.4x10⁴ ≤ Re ≤ 3.2x10⁴ 의레이놀즈수 범위에서 이루어졌으며, 원기둥 후류의 위치별 유속을 측정하여 후류에서 발생되는 와류의 생성에서 소멸까지의 과정 및 와류의 이동 궤적을 조사한 연구이다. 아울러 강제진동실험장치를 이용한 가시화실험을 통하여 풍동실험에서의 결과를 증명하였다. 그 결과 다음과 같은 결과를 얻었다. 1)흐르는 유체에 존재하는 원기둥의 후류에 생성되는 와류의 생성성장소멸 과정을 확인 할 수 있었다. 2) 와류의 퍼짐각도는 16°~17°가량으로 주류속의 변화와 유력진동의 유무에 상관없이 일정하다. 3) 후류에서 변동 유속의 스펙트럼 분석을 통해 와류의 중심이 이동하는 궤적을 유추할 수 있었고, 가시화 실험을 통해 그것을 확신할 수 있다. This experimental study investigated the wake flow around an elastically supported circular cylinder. In this study, the Reynolds numbers are varied in the region of 1.4x10⁴≤ Re ≤3.2x10⁴. Under these conditions, we have captured the process of the wake mechanism and the moving path of the vortex by measuring the velocity at each position in the wake around the cylinder. Further, these facts from the wind tunnel test are proved by a flow visualization test through a water channel. From the result, we have arrived at the following conclusions : i) The process (formation growth collapse) of vortex is observed in the wake around the cylinder, ii) The vortex efflux angle is approximately 16°~17° under the experimental conditions. These angles have no relationship with the velocity change and the existence of flow-induced vibrations of the cylinder, and iii) The moving path of the vortex center is obtained by spectrum analysis of the fluctuating velocity behind the cylinder. These are confirmed by conducting visualization tests.
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