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Greenwater due to plunging breaking wave impingement on a deck structure. Part 2: Impact pressure and air fraction

2026-01-01T00:00:00Z

標題: Greenwater due to plunging breaking wave impingement on a deck structure. Part 2: Impact pressure and air fraction 作者: Hsieh, Meng-Chang; Chuang, Wei-Liang; Lin, Ting-Chieh 摘要: Greenwater generated by plunging wave breakers can impose impulsive and highly localized loads on deck structures, yet the influence of entrained air remains insufficiently quantified because pressure and air fraction are rarely measured at nearly co-located positions. Extending the work of Chuang et al. (2023, Ocean Engineering, 287, 115859), this study simultaneously measures impact pressure and local air fraction on a rigid horizontal deck using a 40-point grid of flush-mounted pressure transducers and fiber-optic reflectometers. Two plunging-wave conditions representing near-edge and more inboard impacts were each repeated 30 times. Incident-wave repeatability and bootstrap convergence analyses were used to assess the adequacy of local ensemble means. Results show a narrow primary pressure peak when the water-rich plunging tongue reaches the deck, followed in some cases by delayed reloading associated with deformation and collapse of entrapped air cavities. The maximum ensemble-averaged pressure reached 15.58 kPa at X50-Z60 under the inboard-impact condition. Air-fraction measurements indicate rapid wetting near the lower probes and intermittent aeration near the upper probes. Higher local air fraction was associated with lower normalized peak pressure under the tested conditions, although the weak correlations and the influence of impact velocity and morphology preclude an isolated causal interpretation.

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

2026-01-01T00:00:00Z

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.

Development of Integrated Geomorphological and Hydrological GIS Platform for Prospective Dam Site Analysis

2026-01-01T00:00:00Z

標題: Development of Integrated Geomorphological and Hydrological GIS Platform for Prospective Dam Site Analysis 作者: Lee, Kwan Tun; Hsu, Yu-Han; Hung, Meng-Chiu; Huang, Pin-Chun; Chien, Ta-Chun; Lin, Yi-Ting; Liao, Yu-Hsun; Chen, Nai-Kuang; Hsu, Ching-Wen; Li, Ciao-Ru; Yang, Cho-Min; Chen, Lo-Ya; Chen, Jia-Qian; Ho, Jui-Yi; Lin, He-Chung; Lin, You-Huei; Tsai, Xiaoang 摘要: Constructing new reservoirs to ensure a reliable water supply in downstream areas and to alleviate overflow flooding along rivers during floods is an urgent task for the authorities. In this study, we developed a GIS platform that integrates a series of watershed geomorphological and hydrological models to assess the suitability of prospective dam sites. The built-in modules include watershed geomorphological analysis, rainfall analysis, flow analysis, surplus water analysis, and reservoir analysis. Using the digital elevation model, users can obtain the reservoir H-A-V curve at a prospective dam site and the upstream watershed's geomorphological factors. A topography-based hydrological model was used to estimate available water at the dam site, and surplus water was obtained by subtracting existing water demands and/or environmental flow requirements from the available water series. Exceedance probability analysis was then conducted for the surplus water to evaluate the dam site's feasibility for new water resources development. The system also provides a reservoir's useful-life evaluation to determine the time required for sediment accumulation to render the reservoir unable to serve its intended purpose. Moreover, for flood control, the platform includes a built-in module for estimating design discharge for different return periods. The planned Pingxi Reservoir site in New Taipei County, Taiwan, is used as an example in this study. Detailed analytical procedures are presented to demonstrate the use of the proposed integrated GIS platform system to assess the adequacy of prospective dam sites for new water resources development.

Onshore U-OWC Wave Energy Converter: A Hydrodynamic Study of Its Capture Performance Impacted by Air-Compressibility Effects

2026-01-01T00:00:00Z

標題: Onshore U-OWC Wave Energy Converter: A Hydrodynamic Study of Its Capture Performance Impacted by Air-Compressibility Effects 作者: Chow, Yi-Chih; Chang, Hong-Yang; Nguyen, Duy Tong; Lin, Chen-Chou 摘要: The distinct engineering advantages of Oscillating Water Column (OWC) systems have driven substantial academic interest lately. This work examines the onshore U-shaped OWC (U-OWC), selected for its cost-effective installation integrated with existing coastal infrastructure and its superior broadband response to diverse wave climates. Time-domain CFD simulations, incorporating the scaling-rematched approach, were conducted to quantify key hydrodynamic and air-compressibility coefficients, including the amplitude of the wave exciting force, fluid damping coefficient, added mass, absorption factor, and the effective PTO (power take-off) damping and air-compressibility coefficients. These parameters collectively elucidate the underlying hydrodynamics and how they are interwoven with the compressibility of the air in the plenum chamber, thereby impacting the U-OWC's energy-capture performance under incident waves. A principal finding is the identification of a C+ interval wherein air compressibility enhances capture performance in the lower wave-period range examined (<8.0 s). The added mass of the present U-OWC exhibits a remarkably pronounced decrease around the wave period of 8.0 s, which can be verified by a simple resonance formula of heave buoys to underline its strong near-resonance behavior.