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Infragravity oscillations in a coupled-basin marina under typhoon conditions: physical model experiments and numerical modeling

Tue, 01 Sep 2026 00:00:00 GMT

標題: Infragravity oscillations in a coupled-basin marina under typhoon conditions: physical model experiments and numerical modeling 作者: Shih-Feng Su; Chia-Hsuan She; Chia-Hsuan She; Jia-Lin Chen; Jia-Lin Chen; Chen-Hsun Wei; Chen-Hsun Wei; Zhi-Cheng Huang; Zhi-Cheng Huang 摘要: Harbor tranquility in marinas can be significantly affected by long-period infragravity oscillations during energetic events, yet existing design guidelines still rely primarily on short-period swell–sea wave criteria. This study investigates infragravity oscillations in a coupled-basin marina at Badouzi Harbor in northern Taiwan, using high-resolution physical model experiments and a non-hydrostatic XBeach model. The XBeach model reproduced significant wave heights in both the swell–sea and infragravity bands reasonably well. The results indicate that swell–sea waves in the inner basin generally satisfy the conventional tranquility criterion of 0.5 m under typhoon conditions, whereas infragravity waves exceed this threshold in both the inner and outer basins. Resonance analysis further reveals that longer infragravity oscillations (100–250 s) dominate the inner basin, accounting for more than 70% of the total infragravity energy and exhibiting Helmholtz-mode behavior that can generate strong oscillatory currents at the basin connection. In contrast, the outer basin retains a broader infragravity band expected to influence the motions of moored yachts. These findings demonstrate that harbor layouts optimized for short-wave sheltering may remain vulnerable to infragravity-induced resonance and associated currents in marina design and operational management.

MQ-RBF with an optimal value of shape parameter determined by a size-independence technique

Thu, 01 Jan 2026 00:00:00 GMT

標題: MQ-RBF with an optimal value of shape parameter determined by a size-independence technique 作者: Liu, Chein-Shan; Tsai, Chia-Cheng 摘要: This paper proposes a new method to find the optimal value of shape parameter in the multiquadric radial basis function (MQ-RBF), which is formulated by a size-independence technique (SIT). The size n for a high-dense MQ-RBF is reduced to m < n, with n simultaneously denoting the number of radial bases, the number of unknown coefficients and the dimension of linear system. Then a lower m-dimensional linear system is solved several times to determine the optimal value of shape parameter, using the golden section search algorithm to minimize the maximal error to fit the given data. Inserting the optimal value obtained from a lower m dimensional linear system into a high-dense MQ-RBF, one can construct a highly accurate interpolant. To solve elliptic type equations we adapt the MQ-RBF by SIT. For searching a good shape parameter in the high-dense MQ-RBF the SIT can improve the accuracy and save CPU time.

Scattering of water waves in the presence of multiple porous structures over trench-type bottom topography

Thu, 01 Jan 2026 00:00:00 GMT

標題: Scattering of water waves in the presence of multiple porous structures over trench-type bottom topography 作者: Sahoo, Gagan; Tsai, Chia-Cheng; Behera, Harekrushna; Hsu, Tai-Wen 摘要: The present study examines the effectiveness of multiple finite-width porous structures in mitigating wave impact on the shorelines featuring trench-type bottom seabed. Wave propagation through thick porous structures is represented using the Sollitt and Cross model, utilizing the principles of small-amplitude water wave theory. The boundary value problem is converted into a system of linear algebraic equations through the eigenfunction expansion method, which is then solved numerically. The findings indicate that increasing the number of porous structures and trenches enhances wave reflection while reducing wave transmission. Analysis of the reflection coefficient's variation with wavenumber for various numbers of trenches and porous structures shows that wave reflection exhibits harmonic peaks followed by subharmonic peaks, with the amplitude of these peaks increasing up to certain wavenumbers before diminishing for higher wavenumbers. The scattering coefficients exhibit oscillatory and periodic patterns in response to changes in the spacing between trenches, porous structures, and the distance from the last trench to the first porous structure. Additionally, oscillatory and periodic patterns are observed in scattering coefficients as a function of trench width. In contrast, as the width of the porous structures increases, the wave reflection exhibits an oscillatory increasing pattern before eventually stabilizing at larger widths. Meanwhile, the transmission coefficient decreases and ultimately becomes zero. Furthermore, higher frictional coefficients result in an increased wave reflection and decreased wave transmission. However, a lower free surface elevation in the lee-side region Rt compared to the region R1 occurs due to multiple porous structures and trenches. With three trenches and four porous structures, the transmission coefficient is reduced to less than 3% , leading to a negligible free surface elevation in Rt . Notably, as the number of porous structures increases, the free surface elevation on the lee-side continues to decrease, even when the quantity of rubble mounds remains constant. This study underscores the potential of multiple porous structures in combination with trench-type bottoms for effective coastal protection.

Development of Next-Generation Flood Inundation Maps: A Case Study in Kaohsiung City, Taiwan

Thu, 01 Jan 2026 00:00:00 GMT

標題: Development of Next-Generation Flood Inundation Maps: A Case Study in Kaohsiung City, Taiwan 作者: Hsu, Chih-Hung; Jang, Jiun-Huei; Chang, Che-Hao; Lee, Wei-Lin; Chien, Chia-Chen; Chung, Po-Hsien 摘要: Flood inundation mapping has become a critical reference for flood risk management, particularly for determining insurance premiums and formulating mitigation strategies in rapidly urbanizing areas with high population density. With recent advancements in mapping technologies and high computing capacity, high-resolution spatiotemporal datasets can be integrated into flood simulation models. In this study, a hydrological digital elevation model (HyDEM) was implemented at the city scale for Kaohsiung City, Taiwan, to improve urban flood simulations. The HyDEM incorporated specialized datasets, including high-resolution DEM, building layer, bankline layer, and seadike layer. Using the Delft3D FM 1D-2D modeling platform, 10 basin-scale models were constructed across Kaohsiung City, and multiresolution computational meshes were employed to achieve a balance between simulation accuracy and computational efficiency. Model performance was validated using two historical flood events, during which it achieved an overall accuracy of similar to 84% for the June 5 Rainstorm event and 80% for the Typhoon Gaemi (2024) event. These results indicate that flood inundation maps (FIMs) can be considerably improved by preserving critical topographic features, particularly building footprints and hydraulic structures such as river and sea dikes. The proposed method thus addresses limitations of earlier generations of FIMs and provides a framework for advancing next-generation flood inundation maps.