This study examines land-based oscillating water column (OWC) devices numerically and experimentally subjected to the action of regular and irregular waves. The higher-order boundary element method was used to develop the numerical model for the simulation of a single- and dual-chamber OWC. A comparison of the performance of both structures is presented. The JONSWAP spectrum method was employed to generate the irregular waves. Physical experiments were conducted to validate the accuracy of the numerical results and demonstrate the variation of aerodynamic and viscous damping effects in the two device configurations. The dual-chamber configuration is proved to broaden the effective frequency bandwidth. The addition of the internal wall reduces the higher-order wave components inside the chamber. The single-chamber OWC efficiency in irregular wave conditions is approximately 5-12 % lower than in regular wave conditions. The dual-chamber OWC efficiency is reduced at the resonance condition in irregular waves but improved in the low wavefrequency region. It is shown that partial sloshing inside the chambers always occurs under the action of the irregular waves, and this phenomenon is more frequently observed in short period waves. A bottom slope is introduced to enhance the dual-chamber converter peak efficiency in the low-frequency, irregular wave conditions whilst the flat-bottomed OWC demonstrates a wider overall effective frequency bandwidth. The hydrodynamic efficiency of the individual chambers in the OWC is less sensitive to significant wave heights; a finding which contrasts with the case of regular waves.
Study on the coral reef canopy hydrodynamics not only provides guidance for the health of coral reef ecosystem and the ecological restoration project,but also supports the decision-making process for the reef coast hazard prevention and mitigation under extreme wave events such as the typhoons.Meanwhile,it also has signific-ant value for predicting the sediment transport over the reef and the reef coast evolution.This paper reviews the state-of-the-art research on reef canopy hydrodynamics,and systematically summarize the research progress from three aspects:the flows inside and outside of reef canopy,the characteristics of canopy resistance as well as the sim-ulation of canopy resistance.This paper finally proposes the further research directions as follows:future study can focus on the hydrodynamics under more severe wave condition or under combined action of wave and current.It should also fully consider the anisotropy of canopy skeleton.Moreover,it can solve the Navier-Stokes equations directly to reproduce the finer flow field at the canopy scale.
The quantification of transparent exopolymer particles（TEP） by colorimetric method is of large error and low repeatability,one major reason of which is related to the absence of clear definition and evaluation for part steps of the original method.It is obscure that the 80% sulfuric acid solution,acted as the extraction solution in the determination of TEP,is prepared based on a volume ratio or mass ratio.Furthermore,the change of solubility of recently available Gum Xanthan（GX） from the market means that the original protocol is no longer applicable,and the grinding of GX stock solution with a tissue grinder is replaced by shaking with a rotating shaker in the study to prevent the excessive dissolution of GX.We found that different preparation techniques could result in the varied concentrations of 80% H 2 SO 4 .The duration of shaking during the preparation of standard solution significantly affected the slope of the calibration curve,which caused different correction results of TEP.The impacts of different extraction solution concentrations and shaking time of GX solution on the quantification of TEP were investigated based on the field sampling and laboratory analysis.The extraction capacities of H 2 SO 4 with different concentrations for Alcian Blue were distinct,but had limited effect on the final measuring result of TEP.The change of the standard curve slope came along with the variation of shaking time,which markedly altered the detection limit and calibration result,and the extended shaking time was in favor of the determination of low-concentration TEP.It was suggested that the extraction solution concentration,shaking time and filtration volume of standard solution are required to be well controlled and selected to obtain more accurate results for TEP with different concentrations.
The observation and detection of the subsea environment urgently require large-scale and long-term observation platforms. The design and development of subsea AUVs involve three key points: the subsea-adapted main body structure, agile motion performance that adapts to complex underwater environments, and underwater acoustic communication and positioning technology. This paper discusses the development and evolution of subsea AUVs before proposing solutions to underwater acoustic communication and positioning navigation schemes. It also studies key technologies for the agile motion of subsea AUVs and finally gives an example of a solution for implementing underwater AUVs, i.e., the disk-shaped autonomous underwater helicopter (AUH). This paper will provide guidance for the design of subsea AUVs and the development of corresponding observation and detection technologies.
Using observational data from multiple satellites, we studied seasonal variations of the shape and location of the Luzon cold eddy (LCE) northwest of Luzon Island. The shape and location of the LCE have obvious seasonal variations. The LCE occurs, develops, and disappears from December to April of the next year. During this period, the shape of the LCE changed from a flat ellipse to a circular ellipse, and the change in shape can be reflected by the increase of the ellipticity of the LCE from 0.16 to 0.82. The latitude of center location of the LCE changes from 17.4°N to 19°N, and the change in latitude can reach 1.6°. Further study showed that seasonal variation of the northeast monsoon intensity leads to the change in the shape and location of the LCE. The seasonal variation of the LCE shape can significantly alter the spatial distribution of the thermal front and chlorophyll a northwest of the Luzon Island by geostrophic advection.
