变废为宝:“蓝色循环”海洋塑料废物管理新策略

The"Blue Circle"vision,initiated by Zhejiang Province in China,represents a groundbreaking advancement in addressing marine plastic waste.Far more than just an innovative concept,it embodies a future-forward approach to managing marine plastic waste,revealing the untapped potential in what was previously considered mere debris.This initiative,marrying scientific innovation with advanced technology,has been rightfully acknowledged with the prestigious2023 United Nations"Champions of the Earth"award,recognizing its innovative strategy in environmental stewardship(https://www.chinadaily.com.cn/a/202310/31/WS65406475a31090682a5eb9ee.html).

Achieving consistency of flexible surface acoustic wave sensors with artificial intelligence

Flexible surface acoustic wave technology has garnered significant attention for wearable electronics and sensing applications.However,the mechanical strains induced by random deformation of these flexible SAWs during sensing often significantly alter the specific sensing signals,causing critical issues such as inconsistency of the sensing results on a curved/flexible surface.To address this challenge,we first developed high-performance AlScN piezoelectric filmbased flexible SAW sensors,investigated their response characteristics both theoretically and experimentally under various bending strains and UV illumination conditions,and achieved a high UV sensitivity of 1.71 KHz/(mW/cm^(2)).To ensure reliable and consistent UV detection and eliminate the interference of bending strain on SAW sensors,we proposed using key features within the response signals of a single flexible SAW device to establish a regression model based on machine learning algorithms for precise UV detection under dynamic strain disturbances,successfully decoupling the interference of bending strain from target UV detection.The results indicate that under strain interferences from 0 to 1160μεthe model based on the extreme gradient boosting algorithm exhibits optimal UV prediction performance.As a demonstration for practical applications,flexible SAW sensors were adhered to four different locations on spacecraft model surfaces,including flat and three curved surfaces with radii of curvature of 14.5,11.5,and 5.8 cm.These flexible SAW sensors demonstrated high reliability and consistency in terms of UV sensing performance under random bending conditions,with results consistent with those on a flat surface.

Detached-eddy simulation of turbulent coherent structures around groynes in a trapezoidal open channel

The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation(DES).A series of short groynes were included on a 1:3 side slope of the channel.This work focuses on the turbulent coherent structures around groynes on an uneven bottom.Flows around groyne fields are characterized by massive separation and highly unsteady vortices.DES can capture a wide spectrum of eddies at a lower computational cost than the large eddy simulation(LES)or direct numerical simulation(DNS).In the present work,a zonal DES model(ZDES)was used to simulate the flow around groynes.The ZDES model is a modified version of the DES designed to overcome the model-stress depletion(MSD)of the RANS/LES hybrid model.The vortex system consists of the horseshoe vortex(HV)formed at the base of the obstructions,the necklace vortex(NV)that wrapped the groyne tips near the free surface,and the shedding vortex(SV)underneath the free surface.The effects of the incident flow and local topography on the vortex evolution were investigated by analyzing the mean flow structures and the instantaneous turbulent flow fields.Some important vortices cannot be captured because of the averaging process,while some flow structures cannot be observed in the instantaneous flow.The mean flow is only a reflection of the averaging process when complex vortices are present.

Incompressible SPH simulation of solitary wave propagation on permeable beaches

Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few decades.However,most of these studies treat beaches as solid boundaries even though they are often made of porous materials,such as sediment and vegetation.Permeable beaches struck by tsunami-like waves have not been adequately investigated.It is expected that the degree of penneability plays a crucial role in mitigating the impact of the wave.This study examines solitary wave run-ups on sandy beaches using an incompressible smoothed particle hydrodynamics(ISPH)model.The permeability of the beach is considered to be directly related to the diameter of its constituent sand particles.To obtain a satisfactory pressure field,which cannot be achieved using the original ISPH algorithm,the source term of the pressure Poisson equation has been modified based on a higher-order source-term expression.Flows within the porous medium are computed in the same framework as those outside the porous medium.In the current model,no transition zone is needed at the boundary of the porous structure.The wave-attenuation effect of the porous medium is discussed,with a particular focus on the relationship between the mn-up height and grainsize.

Experimental study of water and dissolved pollutant runoffs on impervious surfaces

The water and dissolved pollutant runoffs on impervious surfaces are the essential factor to be considered in design methods to minimize the impacts of the diffuse water pollution. In this paper, experiments are conducted to study the water and dissolved pollutant runoffs on impervious surfaces for different rainfall intensities and surface roughnesses. It is shown that a larger rainfall intensity and a smaller surface roughness reduce the time of concentration and increase the pollutant transport rate. Most of the pollutant runoffs take place at the initial stage of the rainfall. The pollutant transport rate rapidly reaches a peak and then gradually drops to zero.

Modelling large deformation and soil–water–structure interaction with material point method:Briefing on MPM2017 conference

The 1st International Conference on the Material Point Method for ＂Modelling Large Deformation and Soil–Water–Structure Interaction＂（MPM2017）was held in Delft,The Netherlands on 10-13 January 2017.This is the first conference organised by the Anura3D MPM Research Community,following a series of international workshops and symposia previously held in The Netherlands,UK,Spain and Italy,as part of the European Commission FP7 Marie-Curie project MPM-DREDGE.We are delighted to present seven contributions in this Special Column of the Journal of Hydrodynamics,and take this opportunity to announce that the 2nd conference,MPM2019,will be held in Cambridge,UK in January 2019.

MPM simulations of dam-break floods

Owing to its ability of modelling large deformations and the ease of dealing with moving boundary conditions,the material point method is gaining popularity in geotechnical engineering applications.In this paper,this promising Lagrangian method is applied to hydrodynamic problems to further explore its potential.The collapse of water columns with different initial aspect ratios is simulated by the material point method.In order to test the accuracy and stability of the material point method,simulations are first validated using experimental data and results of mature numerical models.Then,the model is used to ascertain the critical aspect ratio for the widely-used shallow water equations to give satisfactory approximation.From the comparisons between the simulations based on the material point method and the shallow water equations,the critical aspect ratio for the suitable use of the shallow water equations is found to be 1.

Study of pollutant transport in depth-averaged flows using random walk method

The random walk particle tracking(RWPT)method is compared with the Eulerian methods in investigating pollutant transport in depth-averaged flows.As a typical representative of the Eulerian model with high performance,the MacCormack scheme with Total Variation Diminishing modification(TVD-Mac)is selected for comparison.Solute concentration is simulated in four case studies.First,both numerical models have been tested in two idealized cases and compared against analytical solutions.Numerical dissipation is observed for TVD-Mac model where the concentration changes abruptly,especially under the circumstances of low resolution and misalignment between the flow direction and grid orientation.On the contrary,simulations by the random walk model achieve higher accuracy in both cases and are free of fictitious oscillations in the vicinity of sharp concentration gradients.Then,the solute oscillation along a one-dimensional hypothetical tidal estuary is simulated,with the RWPT accurately con serving mass and suffering less rm merical diffusion compared with the Eulerian method.Finally,the process of pollutant transport in a Yangzte River reach is predicted by the RWPT.The longitudinal dispersion coefficient DL is calculated accordingly.It is compared favorably with the theoretical/empirical formulae,indicating the validity of the RWPT in solving complex natural problems.

Numerical investigation of shallow wake behind a patch of rigid emergent vegetation

The shallow water flow through and around a patch of rigid emergent vegetation was investigated numerically. The mean flow field and turbulent structures were studied, especially their dependence on the solid volume fraction (SVF) of the patch and the bed friction. Two streamwise velocity scales, U1s at the starting point of the steady wake and U1e at the downstream end of the steady wake, and the length of the steady wake L1 were used to describe the steady wake behind the patch. U1s was found to be related to SVF only. However, U1e and L1 were influenced by both the SVF and the wake stability parameter S. For a sparse patch, U1e was equal to U1s, and L1 decreased with the increase of S. For a mid-dense patch, U1e was always smaller than U1s, and it increased with S and gradually approached U1s. The increase of U1e reduced the lateral velocity difference between the flows inside and outside the wake, which resulted in the increase of L1. For a highly dense patch, U1e and L1 did not increase unless S was larger than a critical value. A new parameter, r, was proposed to represent the development rate of the steady wake. The numerical results showed that r increased monotonously with S for mid-dense patches.