Session: 10-06-01: Fluid Measurements and Instrumentation

Paper Number: 142472

142472 - Concurrent Vortex-Shedding and Surface-Wave Phenomena Around a Horizontal Circular Cylinder Close to a Free Surface 

A fully submerged horizontal circular cylinder close to a free surface moves horizontally below the free surface in a still fluid. Vortex shedding and surface waves are observed according to the relevant Froude number (based on the cylinder diameter) and the gap ratio (distance between the cylinder and the free surface non-dimensionalized by the cylinder diameter). Both constrained and unconstrained cases are considered in terms of the vertical motion of the cylinder due to the vortex shedding. Overall, associated with the vortex shedding, five different surface-wave phenomena are observed; no waves, small-amplitude waves, surging breaking waves, collapsing breaking waves (observed only in unconstrained cases), straight-streamline jet-like flows over the upper surface of the cylinder. In the case of no wave motion and small amplitude wave, Karman vortex is formed. However, in the surging wave, a new vortex layer is formed when the free surface is broken due to abrupt deformation of the free surface. This vortex layer affects the vortex shedding behind a cylinder, so that the oscillating amplitude of the cylinder is not constant. When the vibration of the cylinder become significantly larger, a collapsing wave is formed and the oscillating amplitude of the cylinder is kept constant. Jet-like flow is a diagonal flow formed at a close distance from the free surface to the cylinder surface, suppressing vortex shedding and reducing cylinder vibration. In particular, for a constant gap ratio, the jet-like flow becomes steeper as the Froude number increases and, for a constant Froude number, the jet-like flow becomes steeper as the gap ratio decreases. In the presence of a free surface, there have been few studies involving both constrained cylinders and unconstrained cylinders. Therefore, the results of this study are expected to help to analyze the hydrodynamic characteristics that occur when an underwater structure is placed close to a free surface.

Presenting Author: Dongmin Shin Gyeongsang National University

Presenting Author Biography: Wontak Choi, Sanggon Lee, Seungyeop Baek, Seunghyun Lee, Jaedeok Seo, Dongmin Shin, Hyomin Jeong, Daehyeon Kim and Yonmo Sung, 2023. “Numerical analysis of thermal and hydrodynamic characteristics in aquaculture tanks with different tank structures”, Ocean Engineering, 287, 115880.

Dongmin Shin, Yonmo Sung, Hyomin Jeong, Daehyeon Kim and Byungyoung Moon, 2023. “Evaluation of Parametric Roll Mode applying the IMO Second Generation Intact Stability Criteria for 13K Chemical Tanker”, Journal of Marine Science and Engineering, 11(7), 1462.

Dongmin Shin and Byungyoung Moon, 2022. “Assessment of excessive acceleration of the IMO second generation intact stability criteria for the tanker”, Journal of Marine Science and Engineering, 10(2), 229.

Dongmin Shin and Jaeho Chung, 2022. “Wave induced vibration of a fully submerged horizontal cylinder close to a free surface: a theory and experiment”, Ships and Offshore Structures, 17(8), 1843-1851.

Dongmin Shin and Jaeho Chung, 2021. “Application of dead ship condition based on IMO second-generation intact stability criteria for 13K oil chemical tanker”, Ocean Engineering, 238, 109776.

Dongmin Shin, Byungyoung Moon and Jaeho Chung, 2021. “Application of surf-riding and broaching mode based on IMO second-generation Intact stability criteria for previous ships”, International Journal of Naval Architecture and Ocean Engineering, 13, 545-553.

Dongmin Shin, Young Eui Yang, Seung Ryong Baek and Jaeho Chung, 2021. “Development of a loaded vehicle enforcement system using learning-based image processing analysis”, Journal of the Korea Academia-Industrial cooperation Society, 22(11), 788-793.

Jaeho Chung, Jeong Ju Kim and Dongmin Shin*, 2021. “Vehicle Height Detection System using Deep Learning-based Image Processing”, Journal of the Korea Academia-Industrial cooperation Society, 22(7), 621-626.

Jaeho Chung, Dongmin Shin, Won-Don Kim and Byungyoung Moon, 2020. “Current status of the 2nd generation of intact stability; especially investigation of the pure loss of stability and parametric roll mode”, Journal of Ocean Engineering and Technology, 34(2), 55-65.

Dongmin Shin and Byungyoung Moon, 2020. “Viscous mean drift forces on a floating vertical cylinder in waves and currents”, Journal of the Korea Academia-Industrial cooperation Society, 21(3), 503-509.

Dongmin Shin, Youncheol Kim and Byungyoung Moon, 2020. “Mean viscous drift forces on a fixed vertical cylinder in waves and currents”, Journal of the Korea Academia-Industrial cooperation Society, 21(2), 521-527.

Jaeho Chung, Dongmin Shin, Youncheol Kim and Byungyoung Moon, 2020. “An experimental study for predicting the electric power of the coaxial accelerator type wave power generator”, Journal of the Korea Academia-Industrial cooperation Society, 21(2), 19-24.

Dongmin Shin, Kyung-Gun Oh and Byungyoung Moon, 2019. “Development of a computation code for the verification of the vulnerability criteria for surf-riding and broaching based on IMO Second Generation Intact Stability Criteria”, Journal of Ocean Engineering and Technology, 33(6), 518-525.

Dongmin Shin and Yeunwoo Cho, 2016. “Diffraction of waves past two vertical thin plates on the free surface: a comparison of theory and experiment”, Ocean Engineering, 124, 274-286.

Authors:

Dongmin Shin Gyeongsang National University