Wave boundary layers in rough turbulent flow     

Tai-Wen Hsu  Shan-Hwei Ou 《Ocean Engineering》1997,24(1):25-43

A one-layer time-invariant eddy viscosity model is specified to develop a mathematical model for describing the essential features of the turbulent wave boundary layer over a rough bed. The functional form of the eddy viscosity is evaluated based on a modified one-equation turbulence model in which the eddy viscosity varies in time and space. The present eddy viscosity model simplifies much of the mathematical complexity in many existing models. Predictions from the present model have been compared favorably with a wide range of experimental data. It is found that the eddy viscosity model adopted in the present study is physically reasonable.  相似文献   

A study of transient responses of a submerged spherical shell under shock waves   总被引：1，自引：0，他引：1  

Cho-Chung Liang  Ching-Yu Hsu  Wen-Hao Lai 《Ocean Engineering》2001,28(1):22

Based on a procedure which couples the finite element method with the doubly asymptotic approximation, this work addresses the problem of the transient responses of a submerged spherical shell subjected to strong, plane, incident shock waves, in which elastoplastic material behavior is considered. Simulation results indicate that the procedure adopted shows good agreement with related literature, which considered linear elastic behavior of the shell. Also presented herein are the time histories of surface pressure, radial velocity and von Mises stress of the shell. Moreover, deformation diagrams and spreading of the plastic zone of the shell are described as well.  相似文献   

Physical impact on the reclamation area resulting from offshore dredging at the Changhwa coast, Taiwan     

Tai-Wen Hsu  Hsien-Kuo Chang 《Ocean Engineering》2001,28(2):235

The physical impact of offshore dredging on the reclamation area at the Changhwa coast, Taiwan, is investigated using a three-dimensional movable-bed model test. A distorted modeling law consisting of maintaining similarity of the equilibrium beach profile between the model and prototype is proposed. The geometric distortion was verified through a series of preliminary experiments conducted in a wave flume. Experimental results show that the distorted modeling is able to reproduce the beach-face slope in nature. An appropriate long-term morphological time-scale was determined based on a comparison of model longshore littoral transport rates and equivalent prototype values. Seabed topographical changes before and after offshore dredging are evaluated in model tests. A suitable countermeasure to prevent beach erosion from wave attack along the reclamation area is suggested from the experimental results.  相似文献   

Transient,seasonal and interannual variability of the Taiwan Strait current   总被引：2，自引：0，他引：2  

Chau-Ron Wu  Shenn-Yu Chao  Chun Hsu 《Journal of Oceanography》2007,63(5):821-833

We have constructed a fine-resolution model with realistic bathymetry to study the spatial and temporal variations of circulation in the Taiwan Strait (TS). The TS model with a resolution of 3～10 km derives its open boundary conditions from a larger-scale model. The QSCAT/NCEP winds and AVHRR SST provide forcing at the sea surface. Because of the high resolution in model grids and forcing, the model achieves a previously unavailable level of agreement with most observations. On biweekly time scales surface-trapped current reversals often lead to Strait transport reversals if the northeasterly wind bursts in winter are sufficiently strong. On seasonal time scales the northward current is the strongest in summer since both summer monsoon and pressure gradient force are northward. The summer northward current appears to be relatively unimpeded by the Changyun Rise (CYR) and bifurcates slightly near the surface. With the arrival of the northeast monsoon in fall, downwind movement of China Coastal Water (CCW) is blocked by the northward current near 25.5°N and 120°E. In winter, the northward current weakens even more as the northeasterly monsoon strengthens. The CCW moves downwind along the western boundary; the CYR blocks part of the CCW and forces a U-shaped flow pattern in the northern Strait. Past studies have failed to reveal an anticyclonic eddy that develops on the northern flank of CYR in winter. On interannual time scales a weakened northeast monsoon during El Niño reduces advection of the cold CCW from the north and enhances intrusion of warm water from the south, resulting in warming in the TS.  相似文献   

Numerical studies on typhoon surges in the Northern Taiwan     

Wei-Po Huang  Chiang-An Hsu  Chen-Shan Kung  John Z. Yim 《Coastal Engineering》2007,54(12):883-894

A numerical model for the simulation of typhoon surge has been developed for the coastal areas of the northern Taiwan. Results from the model outputs are then used as a typhoon surge data bank for 7 main estuary areas in this region. The data bank consists of the historical typhoon events from 1980 to 2004. Both characteristic and frequency analyses of the typhoon surge in the coastal region have been studied. Using these data, a relation between the surge height and pressure distribution is obtained. It is shown that, either the numerical model, or the statistical equations presented in this paper, can be used to predict possible surge heights in the estuary areas with sufficient accuracy.  相似文献   

Methods of measuring wind stress over a water surface — Discussions of displacement height and von Karman constant     

Ruo-Shan Tseng  Y. -H. L. Hsu  Jin Wu 《Boundary-Layer Meteorology》1992,58(1-2):51-68

Experiments were conducted in a wind-wave tank to study the long-standing discrepancy between wind stresses over a water surface determined with the profile and eddy-correlation methods. Inasmuch as the eddy-correlation method measures the turbulence flux directly, such a discrepancy is considered as an error in the way the profile data are analyzed. Uncertainties in selections of the zero reference plane for the logarithmic velocity profile and of the value for the von Karman constant are suggested to be major sources of the error. To match the results obtained with two methods, the displacement height needs to vary with wave conditions, and the value of the von Karman constant is also discussed.  相似文献   

Marine 3D seismic volumes from 2D seismic survey with large streamer feathering     

Lin  Liang-Fu  Hsu  Ho-Han  Liu  Char-Shine  Chao  Kuo-Han  Ko  Chia-Chun  Chiu  Shye-Dong  Hsieh  Hsin-Sung  Ma  Yu-Fang  Chen  Song-Chuen 《Marine Geophysical Researches》2019,40(4):619-633

Marine Geophysical Research - Strong ocean current influences a marine seismic survey and forces the streamer off-course from the survey line. The sideway drift of the streamer results in that the...  相似文献   

Spatial variation of abundant picoeukaryotes in the subtropical Kuroshio Current in winter     

Ya-Fan Chan  Chih-Ching Chung  Gwo-Ching Gong  Ching-Wei Hsu 《Marine Ecology》2020,41(1):e12579

To understand the importance of picoeukaryotes in the biogeochemical cycle in the subtropical Kuroshio Current, a year-round survey of the hydrography and the distribution of picoeukaryotes were conducted in four oceanographic cruises from October 2012 to July 2013. In comparison with other seasons, the highest abundancy of photosynthetic picoeukaryotes, with concentrations >10⁴ cells/ml, was observed around the eastern boundary of the Kuroshio in the winter. Accordingly, the composition of picoeukaryotes in this cold season was further studied by a metabarcoding analysis of the 18S rRNA gene. The majority of picoeukaryotes comprised Alveolata, followed by Haptophyta and Stramenopiles. Their composition was diverse in the waters affected by the Kuroshio and in the offshore province. For Haptophyta, in contrast to clade A prevailing in the Kuroshio waters, clade B1, which was considered the host of uncultivated diazotrophic cyanobacterium group A (UCYN-A), appeared only in the offshore area. Similarly, in Stramenopiles, Pseudo-nitzschia spp. and MAST-1D, respectively, dominated in the Kuroshio-influenced and offshore areas. While Alveolata was the most abundant group, the distributions of all lineages were similar. The association between picoeukaryote succession and hydrographic change is yet to be fully understood. Our results will assist future studies on the community composition of picoplankton and their relationship with marine ecology in the region.  相似文献   

Use of stable water isotopes to assess sources and influences of slope groundwater on slope failure     

Tsung‐Ren Peng  Chung‐Ho Wang  Shih‐Meng Hsu  Nai‐Chin Chen  Tai‐Wei Su  Jiin‐Fa Lee 《水文研究》2012,26(3):345-355

This study employs stable oxygen and hydrogen isotopes as natural tracers to assess the headwater of a landslide next to a drainage divide and the importance of the slope's headwater in the study area. The study is undertaken near Wu‐She Township in the mountains of central Taiwan. Because a reservoir is located on the other side of the divide, this study evaluates the relationship between the reservoir water and headwater of the landslide as well. Over a 1‐year period, water samples from September 2008 to September 2009, including local precipitation (LP), Wu‐She Reservoir's water (WSRW), slope groundwater (SGW), upper‐reach stream water (USTW), and down‐reach stream water (DSTW), were analysed for deuterium (δD) and oxygen (δ¹⁸O) stable isotopes. Results indicate that WSRW is the predominant component in SGW: approximately 70% of SGW originates from WSRW and 30% from LP based on a two end‐member mass‐balance mixing model for δ¹⁸O. The similar two end‐member mixing model is also employed to assess the contributions of USTW and SGW to DSTW. Model results indicate that SGW is the major source of DSTW with a contribution of about 67%. Accordingly, about 47% of DSTW sources from the WSRW. In short, owing to reservoir leakage, WSRW contributes the greater part of both SGW and DSTW. Plentiful WSRW in SGW threatens the stability of the slope in the divide area. To avoid subsequent continuous slope failure, necessary mitigation steps are required. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Variation of uncertainty of drainage density in flood hazard mapping assessment with coupled 1D–2D hydrodynamics model     

Yang  Song-Yue  Chang  Che-Hao  Hsu  Chih-Tsung  Wu  Shiang-Jen 《Natural Hazards》2022,111(3):2297-2315

Coupled 1D–2D hydrodynamic models are widely utilized in flood hazard mapping. Previous studies adopted conceptual hydrological models or 1D hydrodynamic models to evaluate the impact of drainage density on river flow. However, the drainage density affects not only river flow, but also the flooded area and location. Therefore, this work adopts the 1D–2D model SOBEK to investigate the impact of drainage density on river flow. The uncertainty of drainage density in flood hazard mapping is assessed by a designed case and a real case, Yanshuixi Drainage in Tainan, Taiwan. Analytical results indicate that under the same return period rainfall, reduction in tributary drainages in a model (indicating a lower drainage density) results in an underestimate of the flooded area in tributary drainages. This underestimate causes higher peak discharges and total volume of discharges in the drainages, leading to flooding in certain downstream reaches, thereby overestimating the flooded area. The uncertainty of drainage density decreases with increased rainfall. We suggest that modeling flood hazard mapping with low return period rainfalls requires tributary drainages. For extreme rainfall events, a lower drainage density could be selected, but the drainage density of local key areas should be raised.

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