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Ocean Systems Engineering Volume 10, Number 2, June 2020 , pages 201-226 DOI: https://doi.org/10.12989/ose.2020.10.2.201 |
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Numerical study on the performance of semicircular and rectangular submerged breakwaters |
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Mohammad Barzegar and D. Palaniappan
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| Abstract | ||
| A systematic numerical comparative study of the performance of semicircular and rectangular submerged breakwaters interacting with solitary waves is the basis of this paper. To accomplish this task, Nwogu\'s extended Boussinesq model equations are employed to simulate the interaction of the wave with breakwaters. The finite difference technique has been used to discretize the spatial terms while a fourth-order predictor-corrector method is employed for time discretization in our numerical model. The proposed computational scheme uses a staggered-grid system where the first-order spatial derivatives have been discretized with fourth-order accuracy. For validation purposes, five test cases are considered and numerical results have been successfully compared with the existing analytical and experimental results. The performances of the rectangular and semicircular breakwaters have been examined in terms of the wave reflection, transmission, and dissipation coefficients (RTD coefficients) denoted by K_R, K_T, K_D. The latter coefficient K_D emerges due to the non-energy conserving K_R and K_T,. Our computational results and graphical illustrations show that the rectangular breakwater has higher reflection coefficients than semicircular breakwater for a fixed crest height, but as the wave height increases, the two reflection coefficients approach each other. On the other hand, the rectangular breakwater has larger dissipation coefficients compared to that of the semicircular breakwater and the difference between them increases as the height of the crest increases. However, the transmission coefficient for the semicircular breakwater is greater than that of the rectangular breakwater and the difference in their transmission coefficients increases with the crest height. Quantitatively, for rectangular breakwaters the reflection coefficients K_R are 5-15% higher while the diffusion coefficients K_D are 3-23% higher than that for the semicircular breakwaters, respectively. The transmission coefficients K_T for rectangular breakwater shows the better performance up to 2.47% than that for the semicircular breakwaters. Based on our computational results, one may conclude that the rectangular breakwater has a better overall performance than the semicircular breakwater. Although the model equations are non-dissipative, the non-energy conserving transmission and reflection coefficients due to wave-breakwater interactions lead to dissipation type contribution. | ||
| Key Words | ||
| Nwogu\'s extended Boussinesq equations; semicircular breakwater; rectangular breakwater; RTD coefficients; performance; finite difference method | ||
| Address | ||
| Mohammad Barzegar: Department of Physical & Environmental Sciences, Texas A&M University, Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412 D. Palaniappan: Department of Mathematics & Statistics, Texas A&M University, Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412 | ||
