Jaeyoung Jung - Academia.edu (original) (raw)
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Papers by Jaeyoung Jung
Ocean Engineering, 2021
This study investigates the macroscopic features of tidal farm layouts optimized to maximize powe... more This study investigates the macroscopic features of tidal farm layouts optimized to maximize power production in an idealized shallow channel with steady unidirectional flow. By varying the number of turbines and optimization constraints, numerical experiments were conducted using OpenTidalFarm, an open-source solver for tidal farm optimization using PDE-constraint gradient-based optimization. To alleviate the computational complexity for identifying a global optimum, a concept of quasi-global optimum was introduced, a local optimum that serves as a global optimum in a crude sense. From extensive numerical results, notable patterns in the shape of the quasi-global optimal layout were observed and explained by a nondimensional parameter, E, the ratio of the shortest hypothetical linear fence to the length of the lateral farm site constraint. The quasi-global optimal layout had a linear fence shape when E ≤ 1. The layout evolved into a downstream-concave parabola and subsequently into a V-shape as E increased beyond 1. Moreover, as more turbines were added to an array, the quasi-global optimal layout was no longer a single fence, and some turbines were separated from the main body. From the quantitative perspective, it is shown that the power production could be increased by up to 50% by tuning the optimization constraints.
38th IAHR World Congress - "Water: Connecting the World", 2019
Water waves have been studied for centuries to understand various physical phenomena related with... more Water waves have been studied for centuries to understand various physical phenomena related with them in the estuary and the coast. In particular, the solitary wave has been a classical research interest over the last 100 years. Meanwhile, the significant improvement of the computation power and resource has helped the numerical studies to solve the partial differential equations representing physical phenomena more precisely and accurately. One of convenctional question could be the gereation of wave numerically. Therefore, this study deals with how to generate solitary waves accurately with a high order numerical method. For comparison with the past experimental studies, a piston type wave-maker is implemented with the higher order method, and which is governed by a conservative form of nonlinear shallow water equation. Numerical experiments are performed with the base on the Boussinesq's solitary waves. The simulated results show that if the ratio of the amplitude to the water depth is large, waves with inadmissible errors are generated. These errors occur due to the violation of a hydrostatic pressure assumption, which is mainly used in shallow water equations, in the particular practical problem such as the relative large variations of the terrain or water surface level compared to the water depth. In order to avoid such errors and increase the accuracy of numerical experiments, nonhydrostatic pressure should be considered explicitly.
Ocean Engineering, 2021
This study investigates the macroscopic features of tidal farm layouts optimized to maximize powe... more This study investigates the macroscopic features of tidal farm layouts optimized to maximize power production in an idealized shallow channel with steady unidirectional flow. By varying the number of turbines and optimization constraints, numerical experiments were conducted using OpenTidalFarm, an open-source solver for tidal farm optimization using PDE-constraint gradient-based optimization. To alleviate the computational complexity for identifying a global optimum, a concept of quasi-global optimum was introduced, a local optimum that serves as a global optimum in a crude sense. From extensive numerical results, notable patterns in the shape of the quasi-global optimal layout were observed and explained by a nondimensional parameter, E, the ratio of the shortest hypothetical linear fence to the length of the lateral farm site constraint. The quasi-global optimal layout had a linear fence shape when E ≤ 1. The layout evolved into a downstream-concave parabola and subsequently into a V-shape as E increased beyond 1. Moreover, as more turbines were added to an array, the quasi-global optimal layout was no longer a single fence, and some turbines were separated from the main body. From the quantitative perspective, it is shown that the power production could be increased by up to 50% by tuning the optimization constraints.
38th IAHR World Congress - "Water: Connecting the World", 2019
Water waves have been studied for centuries to understand various physical phenomena related with... more Water waves have been studied for centuries to understand various physical phenomena related with them in the estuary and the coast. In particular, the solitary wave has been a classical research interest over the last 100 years. Meanwhile, the significant improvement of the computation power and resource has helped the numerical studies to solve the partial differential equations representing physical phenomena more precisely and accurately. One of convenctional question could be the gereation of wave numerically. Therefore, this study deals with how to generate solitary waves accurately with a high order numerical method. For comparison with the past experimental studies, a piston type wave-maker is implemented with the higher order method, and which is governed by a conservative form of nonlinear shallow water equation. Numerical experiments are performed with the base on the Boussinesq's solitary waves. The simulated results show that if the ratio of the amplitude to the water depth is large, waves with inadmissible errors are generated. These errors occur due to the violation of a hydrostatic pressure assumption, which is mainly used in shallow water equations, in the particular practical problem such as the relative large variations of the terrain or water surface level compared to the water depth. In order to avoid such errors and increase the accuracy of numerical experiments, nonhydrostatic pressure should be considered explicitly.