Effects of LIDAR DEM resolution in hydrodynamic modelling: model sensitivity for cross-sections

With the development of science and technology the entire Earth,together with all of its phenomena,is gradually becoming an object of computer digitisation.For several years,this process has also affected water components,which are essential for the development of humans and economies on Earth.Therefore,monitoring of its resources and movement across the Earth’s surface is the main object of investigation of several research institutions.In recent years,hydraulic modelling has experienced significant development that meets water and computer connection conditions.This study consequently dealt with hydraulic modelling and uncertainties in the data that may affect the resulting flood zone.We analysed the effect of cross-sections generated and the subsequent inundation areas in Digital Elevation Models of different resolutions.The basic DEM was constructed from data obtained by the LIDAR method.Hydraulic results were obtained using a one-dimensional(1-D)model,HEC-RAS,and its extension,HEC-GeoRAS.The Olsˇe and Stona´vka river junction,located in the northeast region of the Czech Republic,was selected for investigation.The resolutions selected for the study to generate cross-sections and the subsequent inundation areas were 1 m,5 m and 10 m.The resulting cross-sections were confronted with the actual surveyed cross-sections.

GLOBAL SOLUTIONS TO A HYDRODYNAMIC MODEL FOR SEMICONDUCTORS WITH VELOCITY RELAXATION

In this paper,we apply the method given in the paper“Zero relaxation time limits to a hydrodynamic model of two carrier types for semiconductors”(Mathematische Annalen,2022,382:1031–1046)to study the Cauchy problem for a one dimensional inhomogeneous hydrodynamic model of two-carrier types for semiconductors with the velocity relaxation.

The Hydrodynamic Behaviour of Euboean Gulf Coastal Areas and the Mixing of the Physico-Chemical Characteristics of Urban Sewage Discharged into Them under the Influence of Climate Change

The hydrodynamic circulation within the marine environment is a complex phenomenon, characterized by the interplay of strong tidal forces, atmospheric influences, and bathymetric features. The physical and hydrodynamic attributes of this flow play a pivotal role in promoting vertical mixing of seawater masses, thereby facilitating the integration of their physical and chemical parameters, including nutrients and oxygen. Additionally, they are instrumental in governing the dispersion and diffusion of pollutants originating from urban sewage, contributing to the overall water renewal process and environmental quality. This study investigates the potential impact of anticipated increases in average air temperatures on water column stratification in coastal regions susceptible to these dynamic influences. These areas receive treated urban sewage, and the study aims to assess how these temperature changes might influence the dispersion and mixing of pollutant loads present in these coastal waters.

Lagrangian coherent structure analysis on transport of Acetes chinensis along coast of Lianyungang,China

Spatial heterogeneity or“patchiness”of plankton distributions in the ocean has always been an attractive and challenging scientific issue to oceanographers.We focused on the accumulation and dynamic mechanism of the Acetes chinensis in the Lianyungang nearshore licensed fishing area.The Lagrangian frame approaches including the Lagrangian coherent structures theory,Lagrangian residual current,and Lagrangian particle-tracking model were applied to find the transport pathways and aggregation characteristics of Acetes chinensis.There exist some material transport pathways for Acetes chinensis passing through the licensed fishing area,and Acetes chinensis is easy to accumulate in the licensed fishing area.The main mechanism forming this distribution pattern is the local circulation induced by the nonlinear interaction of topography and tidal flow.Both the Lagrangian coherent structure analysis and the particle trajectory tracking indicate that Acetes chinensis in the licensed fishing area come from the nearshore estuary.This work contributed to the adjustment of licensed fishing area and the efficient utilization of fishery resources.

Hydrodynamic Study on Energy Capturing Performance of Horizontal Axis Blades Under Sub-Low Speed Tidal Current

The research on the hydrodynamics of blades is mainly focused on sea areas with high-speed current.However,the average velocity in most territorial waters of China is smaller than 1 m/s,and the lift type of airfoil blades has limited application in most of these conditions.Therefore,it is of great significance to study the tidal current energy capture of blades in sub-low speed sea areas.The effect of flow impact resistance on the blade at sub-low current speed is considered and a new type of thin-walled blade based on the lift type of blade is proposed,and then the lift-impact combined hydrodynamic model of horizontal axis blade is established.Based on this model,and considering the characteristics of tidal current and velocity in the sea area of Yushan Islands,simulation and optimization of blade design are carried out.Additionally,the horizontal axis thin-walled blade and the NACA airfoil contrast blade under the same conditions are developed.By using a synthetical experimental test system,the power,torque,rotational speed and load characteristics of these two blades are tested.The performance of the thin-walled blade and the design theory are verified.It shows that this type of blade has much better energy capture efficiency in the sub-low speed sea area.This research will promote the study and development of turbines that can be used in low-speed current sea areas in the future.

Stability analysis of multiple-lattice self-anticipative density integration effect based on lattice hydrodynamic model in V2V environment

Under the environment of vehicle-to-vehicle(V2V)communication,the traffic information on a large scale can be obtained and used to coordinate the operation of road traffic system.In this paper,a new traffic lattice hydrodynamic model is proposed which considers the influence of multiple-lattice self-anticipative density integration on traffic flow in the V2V environment.Through theoretical analysis,the linear stability condition of the new model is derived and the stable condition can be enhanced when more-preceding-lattice self-anticipative density integration effect is taken into account.The property of the unstable traffic density wave in the unstable region is also studied according to the nonlinear analysis.It is shown that the unstable traffic density wave can be described by solving the modified Korteweg-de-Vries(mKdV)equation.Finally,the simulation results demonstrate the validity of the theoretical results.Both theoretical analysis and numerical simulations demonstrate that multiple-lattice self-anticipative density integration effect can enhance the stability of traffic flow system in the V2V environment.

A BLOW-UP CRITERION OF STRONG SOLUTIONS TO THE QUANTUM HYDRODYNAMIC MODEL

In this article,we focus on the short time strong solution to a compressible quantum hydrodynamic model.We establish a blow-up criterion about the solutions of the compressible quantum hydrodynamic model in terms of the gradient of the velocity,the second spacial derivative of the square root of the density,and the first order time derivative and first order spacial derivative of the square root of the density.

Application of River Network Hydrodynamic Model in Determining Water Distribution Scale of Haishu Plain

The water distribution network is an important part of the plain water environment improvement system. To make efficient use of the regional water diversion source, scientifically distribute the water diversion flow and improve the water environment carrying capacity of Haishu Plain, the river network hydrodynamic model is used in this paper to simulate the water intake location, reasonable water quantity and influence range of water transfer in Haishu Plain. The simulation results have high accuracy, which can provide a scientific basis for the scale, water transfer mechanism and project layout of water transfer construction in Haishu Plain and show a strong reference value for the study of water diversion and distribution scheme of coastal plain river network.

Rainwater harvesting systems: An urban flood risk mitigation measure in arid areas

Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.

An Improved Approach for Interaction of Wave with Floating Spheres and Its Applications

To develop and utilize marine resources in the deep sea, the higher requirements for floating structures, which are operated in marine environment for a long term, have been put forward. Reasonable structure type and accurate force analysis are favorable guarantees to improve the survival performance and working performance of the floating structures. Floating spheres fastened by mooring cable were widely used in floating structures. In this paper, the wave forces of the floating sphere are efficiently and accurately calculated by solving the geometric relationship between the non-submerged floating sphere and wave surface. Combined with the hydrodynamic calculation of mooring cables based on the lumped mass method, the coupled motion model of multi-floating spheres fastened by multi-mooring cable was established under wave action. Furthermore, according to the floating structures fastened by mooring cable in the actual ocean engineering, the topological method of multi-mooring cables fastening the multifloating spheres was expounded from simple to complex. Finally, the modeling method and preliminarily hydrodynamic characteristics of the fastened floating structures, including the mooring system of renewable energy devices, ocean buoy, and coral nursery, were presented and analyzed in detail. The obtained results showed that the method for calculating the wave force on the floating sphere developed in this paper can accurately describe the motion process of the floating mooring sphere and the force on the mooring cable. Also, the topological method of multiple buoys and multiple mooring cables could efficiently establish various numerical hydrodynamic models of fastened buoys in ocean engineering.

Analytical model of non-uniform charge distribution within the gated region of GaN HEMTs

A physics-based analytical expression that predicts the charge,electrical field and potential distributions along the gated region of the GaN HEMT channel has been developed.Unlike the gradual channel approximation(GCA),the proposed model considers the non-uniform variation of the concentration under the gated region as a function of terminal applied volt-ages.In addition,the model can capture the influence of mobility and channel temperature on the charge distribution trend.The comparison with the hydrodynamic(HD)numerical simulation showed a high agreement of the proposed model with numerical data for different bias conditions considering the self-heating and quantization of the electron concentration.The ana-lytical nature of the model allows us to reduce the computational and time cost of the simulation.Also,it can be used as a core expression to develop a complete physics-based transistorⅣmodel without GCA limitation.

A novel lattice model integrating the cooperative deviation of density and optimal flux under V2X environment

A novel lattice hydrodynamic model is proposed by integrating the cooperative deviation of density and optimal flux under vehicle to X(V2X) environment. According to the theoretical analysis, the stability conditions and the mKdV equations affected by the cooperative deviation of traffic information are explored. And the density wave, hysteresis loop and energy consumption of the traffic flow have been investigated via numerical simulation. The results indicate that the cooperative deviation of density and optimal flux can effectively alleviate the traffic congestion. More importantly, our new consideration can reduce fuel consumption and exhaust emission under the V2X environment.

小间隙大电流真空电弧数值仿真(英文)

The plasma status of vacuum arc before arc current zero,has a great influence on the interruption performance of the vacuum circuit breakers.In this paper,a vacuum arc model in a short gap was established based on the magnet hydrodynamic(MHD) and a common computational fluid dynamics(CFD) software was utilized to specially investigate the properties of this arc.The spatial distributions of plasma pressure,plasma density,ion axial velocity, and axial current density in front of the anode surface of vacuum arc in this case were obtained.Simulation results indicate that:from the cathode to the anode,both of the plasma pressure and the plasma density increase gradually,and the plasma axial velocity decreases gradually;the axial current density in front of anode has a large radial gradient, and the maximum value is still smaller than the threshold current density for the anode-spot formation,thus,the anode is still passive.The comparison between the plasma density of simulation and the CMOS images taken by the high-speed camera indicates that they are in reasonable agreement with each other and demonstrates the feasibility of the vacuum arc model.

Distribution of 9 Principal Tidal Constituents and Tide Prediction for the East China Sea

By use of the hydrodynamic model,the harmonic constants of 8 principal tidal constituents(Q_1,O_1,P_1,K_1,N_2,M_2,S_2andK_2)are obtained for the East China Sea,and the harmonic constant ofS_a is calculated by two-dimensional interpolation.The calculated results agree well with the observed dataaround the sea.The harmonic constants can be used to predict the tide in the East China Sea.The cotidalcharts of the 9 tidal constituents reveal their distribution.

Physical modeling of direct current and radio frequency characteristics for In P-based InAlAs/InGaAs HEMTs

Direct current(DC) and radio frequency(RF) performances of InP-based high electron mobility transistors(HEMTs)are investigated by Sentaurus TCAD. The physical models including hydrodynamic transport model, Shockley–Read–Hall recombination, Auger recombination, radiative recombination, density gradient model and high field-dependent mobility are used to characterize the devices. The simulated results and measured results about DC and RF performances are compared, showing that they are well matched. However, the slight differences in channel current and pinch-off voltage may be accounted for by the surface defects resulting from oxidized InAlAs material in the gate-recess region. Moreover,the simulated frequency characteristics can be extrapolated beyond the test equipment limitation of 40 GHz, which gives a more accurate maximum oscillation frequency( f_(max)) of 385 GHz.

Change of stream network connectivity and its impact on flood control

AbstUrbanization can alter the hydrogeomorphology of streams and rivers,change stream network structures,and reduce stream network connectivity,which leads to a decrease in the storage capacity of stream networks and aggravates flood damage.Therefore,investigation of the ways in which stream network connectivity impacts flood storage capacity and flood control in urbanized watersheds can provide significant benefits.This study developed a framework to assess stream network connectivity and its impact on flood control.First,a few connectivity indices were adopted to assess longitudinal stream network connectivity.Afterward,the static and dynamic storage capacities of stream networks were evaluated using storage capacity indices and a one-dimensional hydrodynamic model.Finally,the impact of stream network connectivity change on flood control was assessed by investigating the changes in stream network connectivity and storage capacity.This framework was applied to the Qinhuai River Basin,China,where intensive urbanization has occurred in the last few decades.The results show that stream network storage capacity is affected by stream network connectivity.Increasing stream network connectivity enhances stream network storage capacity.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Salinity Distribution at Canal Istanbul and Its Possible Impacts on the Northern Marmara Sea

Turkey has announced its plan to construct a new waterway, Canal Istanbul, parallel to the Bosphorus. In this study,the influence of Canal Istanbul on salinity distribution in the northern Marmara Sea is investigated using a previously calibrated 3 D hydrodynamic and salinity model. Moreover, the salinity field of the canal and its propagation are examined based on various meteorological cases. Finally, the flow structure of the canal is determined. It is calculated that at the southern end of the canal, mainly unidirectional flow(from the Black Sea to the Marmara Sea)occurs during 68% of the simulation period. A two-layer flow is seen only 28% of the time with a weak lower layer flow, whereas this value decreases to 4% at the north end of the canal. In the southward direction(to the Marmara Sea), velocities higher than 1.5 m/s are rarely observed along the canal. The average surface salinity difference in the northern Marmara Sea due to the construction of the canal is calculated to be smaller than 0.50 ppt. The salinity difference gradually diminishes as water depth increases and after 25 m(from the surface) almost no difference is observed.

Numerical simulation of nanosecond laser ablation and plasma characteristics considering a real gas equation of state

Based on the governing equations which include the heat conduction equation in the target and the fluid equations of the vapor plasma,a two-dimensional axisymmetric model for ns-laser ablation considering the Knudsen layer and plasma shielding effect is developed.The equations of state of the plasma are described by a real gas approximation,which divides the internal energy into the thermal energy of atoms,ions and electrons,ionization energy and the excitation energy of atoms and ions.The dynamic evolution of the silicon target and plasma during laser ablation is studied by using this model,and the distributions of the temperature,plasma density,Mach number related to the evaporation/condensation of the target surface,laser transmissivity as well as internal energy of the plasma are given.It is found that the evolution of the target surface during laser ablation can be divided into three stages:(1)the target surface temperature increases continuously;(2)the sonic and subsonic evaporation;and(3)the subsonic condensation.The result of the internal energy distribution indicates that the ionization and excitation energy plays an important role in the internal energy of the plasma during laser ablation.This model is suitable for the case that the temperature of the target surface is lower than the critical temperature.

Drift vortices in inhomogeneous collisional dusty magnetoplasma

For the sake of investigating the drift coherent vortex structure in an inhomogeneous dense dusty magnetoplasma,using the quantum hydrodynamic model a nonlinear controlling equation is deduced when the collision effect is considered.New vortex solutions of the electrostatic potential are obtained by a special transformation method, and three evolutive cases of monopolar vortex chains with spatial and temporal distribution are analyzed by representative parameters. It is found that the collision frequency, particle density, drift velocity, dust charge number, electron Fermi wavelength, quantum correction,and quantum parameter are all influencing factors of the vortex evolution. Compared to the uniform dusty system, the vortex solutions of the inhomogeneous system present richer spatial evolution and physical meaning. These results may explain corresponding vortex phenomena and support beneficial references for the dense dusty plasma atmosphere.

Simulation of Flood in the Thach Han-Ben Hai River Basin(Vietnam)under the Influence of the Upstream Reservoir System

The central provinces in Vietnam always suffer from the negative impacts of floods every year,especially in the downstream areas.Quang Tri province in the TBRB(Thach Han-Ben Hai River Basin)is one of the provinces suffering heavy damage caused by floods.A 1-dimensional hydrodynamic model was researched and applied connecting 2 dimensions in the MIKE model set(MIKE FLOOD)to simulate inundation level,inundation time,flood flow velocity for communes in TBRB.Simulation results for 111 communes in Quang Tri province show that:39 communes(35%)are not flooded;3 communes are flooded below 0.5 m;15 communes are flooded from 0.5-1.0 m,flooding time is about 1 day;30 communes are flooded from 1.0-2.0 m,inundation time is about 2 days;30 communes are flooded over 2.0 m,flooded for about 3 days,especially 3 communes are flooded over 4.0 m.This result helps to develop flood prevention plans for localities in the province.