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103 results on '"Hong, Keyyong"'

8. Ocean Energy Systems Wave Energy Modeling Task 10.4: Numerical Modeling of a Fixed Oscillating Water Column

Author

Bingham, Harry, Yu, Yi-Hsiang, Nielsen, Kim, Tran, Thanh Toan, Kyong-Hwan, Kim, Park, Sewan, Hong, Keyyong, Said, Hafiz Ahsan, Kelly, Thomas, Ringwood, John, Read, Robert, Ransley, Edward, Brown, Scott, Greaves, Deborah, Bingham, Harry, Yu, Yi-Hsiang, Nielsen, Kim, Tran, Thanh Toan, Kyong-Hwan, Kim, Park, Sewan, Hong, Keyyong, Said, Hafiz Ahsan, Kelly, Thomas, Ringwood, John, Read, Robert, Ransley, Edward, Brown, Scott, and Greaves, Deborah

Abstract

This paper reports on an ongoing international effort to establish guidelines for numerical modeling of wave energy converters, initiated by the International Energy Agency Technology Collaboration Program for Ocean Energy Systems. Initial results for point absorbers were presented in previous work, and here we present results for a breakwater-mounted Oscillating Water Column (OWC) device. The experimental model is at scale 1:4 relative to a full-scale installation in a water depth of 12.8 m. The power-extracting air turbine is modeled by an orifice plate of 1–2% of the internal chamber surface area. Measurements of chamber surface elevation, air flow through the orifice, and pressure difference across the orifice are compared with numerical calculations using both weakly-nonlinear potential flow theory and computational fluid dynamics. Both compressibleand incompressible-flow models are considered, and the effects of air compressibility are found to have a significant influence on the motion of the internal chamber surface. Recommendations are made for reducing uncertainties in future experimental campaigns, which are critical to enable firm conclusions to be drawn about the relative accuracy of the numerical models. It is well-known that boundary element method solutions of the linear potential flow problem (e.g., WAMIT) are singular at infinite frequency when panels are placed directly on the free surface. This is problematic for time-domain solutions where the value of the added mass matrix at infinite frequency is critical, especially for OWC chambers, which are modeled by zero-mass elements on the free surface. A straightforward rational procedure is described to replace ad-hoc solutions to this problem that have been proposed in the literature.

Published
2021

9. Ocean Energy Systems Wave Energy Modeling Task 10.4: Numerical Modeling of a Fixed Oscillating Water Column

Author

Bingham, Harry B., Yu, Yi-Hsiang, Nielsen, Kim, Tran, Thanh Toan, Kim, Kyong-Hwan, Park, Sewan, Hong, Keyyong, Said, Hafiz Ahsan, Kelly, Thomas, Ringwood, John V., Read, Robert W., Ransley, Edward, Brown, Scott, Greaves, Deborah, Bingham, Harry B., Yu, Yi-Hsiang, Nielsen, Kim, Tran, Thanh Toan, Kim, Kyong-Hwan, Park, Sewan, Hong, Keyyong, Said, Hafiz Ahsan, Kelly, Thomas, Ringwood, John V., Read, Robert W., Ransley, Edward, Brown, Scott, and Greaves, Deborah

Abstract

This paper reports on an ongoing international effort to establish guidelines for numerical modeling of wave energy converters, initiated by the International Energy Agency Technology Collaboration Program for Ocean Energy Systems. Initial results for point absorbers were presented in previous work, and here we present results for a breakwater-mounted Oscillating Water Column (OWC) device. The experimental model is at scale 1:4 relative to a full-scale installation in a water depth of 12.8 m. The power-extracting air turbine is modeled by an orifice plate of 1–2% of the internal chamber surface area. Measurements of chamber surface elevation, air flow through the orifice, and pressure difference across the orifice are compared with numerical calculations using both weakly-nonlinear potential flow theory and computational fluid dynamics. Both compressible- and incompressible-flow models are considered, and the effects of air compressibility are found to have a significant influence on the motion of the internal chamber surface. Recommendations are made for reducing uncertainties in future experimental campaigns, which are critical to enable firm conclusions to be drawn about the relative accuracy of the numerical models. It is well-known that boundary element method solutions of the linear potential flow problem (e.g., WAMIT) are singular at infinite frequency when panels are placed directly on the free surface. This is problematic for time-domain solutions where the value of the added mass matrix at infinite frequency is critical, especially for OWC chambers, which are modeled by zero-mass elements on the free surface. A straightforward rational procedure is described to replace ad-hoc solutions to this problem that have been proposed in the literature.

Published
2021

11. Ocean Energy Systems Wave Energy Modeling Task 10.4: Numerical Modeling of a Fixed Oscillating Water Column

Author

Bingham, Harry B., primary, Yu, Yi-Hsiang, additional, Nielsen, Kim, additional, Tran, Thanh Toan, additional, Kim, Kyong-Hwan, additional, Park, Sewan, additional, Hong, Keyyong, additional, Said, Hafiz Ahsan, additional, Kelly, Thomas, additional, Ringwood, John V., additional, Read, Robert W., additional, Ransley, Edward, additional, Brown, Scott, additional, and Greaves, Deborah, additional

Published
2021
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34. A Study of the Appearance Characteristics and Generation Mechanism of Giant Waves

Author

Shin Seung-Ho and Hong Keyyong

Subjects
Physics, Nonlinear system, Optics, Airy wave theory, business.industry, Wave propagation, Wave height, Breaking wave, Mechanics, Mechanical wave, business, Wave train, Longitudinal wave
Abstract

In the wave spectrum distribution based on linear wave theory, the appearance of a giant wave whose wave height reaches to 30m has been considered next to almost impossible in a real sea However since more than 10 giant waves were observed in a recent investigation of global wave distribution which was carried out by the analysis of SAR imagines for three weeks, the existence of the giant waves is being recognized and it is considered the cause of many unknown marine disasters. The change of wave height distribution concerning a formation of wave train, nonlinear wave to wave interaction and so on were raised as the causes of the appearance of the giant waves, but the occurrence mechanism of the giant waves hasn`t been cleared yet. In present study, we investigated appearance circumstances of the giant waves in real sea and its occurrence mechanism was analyzed based on linear and nonlinear wave focusing theories. Also, through a development of numerical model of the nonlinear equation, the formations of the giant wave from progressive wave train were reproduced.

Published
2006

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