Application of Smoothed Particle Hydrodynamics(SPH)for the Simulation of Flow-Like Landslides on 3D Terrains

Flow-type landslide is one type of landslide that generally exhibits characteristics of high flow velocities,long jump distances,and poor predictability.Simulation of its propagation process can provide solutions for risk assessment and mitigation design.The smoothed particle hydrodynamics(SPH)method has been successfully applied to the simulation of two-dimensional(2D)and three-dimensional(3D)flow-like landslides.However,the influence of boundary resistance on the whole process of landslide failure is rarely discussed.In this study,a boundary condition considering friction is proposed and integrated into the SPH method,and its accuracy is verified.Moreover,the Navier-Stokes equation combined with the non-Newtonian fluid rheologymodel was utilized to solve the dynamic behavior of the flow-like landslide.To verify its performance,the Shuicheng landslide event,which occurred in Guizhou,China,was taken as a case study.In the 2D simulation,a sensitivity analysis was conducted,and the results showed that the shearing strength parameters have more influence on the computation accuracy than the coefficient of viscosity.Afterwards,the dynamic characteristics of the landslide,such as the velocity and the impact area,were analyzed in the 3D simulation.The simulation results are in good agreement with the field investigations.The simulation results demonstrate that the SPH method performs well in reproducing the landslide process,and facilitates the analysis of landslide characteristics as well as the affected areas,which provides a scientific basis for conducting the risk assessment and disaster mitigation design.

Numerical and experimental study on the particle erosion and gas–particle hydrodynamics in an integral multi-jet swirling spout-fluidized bed

In this paper,using the computational fluid dynamics based on Euler Lagrange and the commercial software Barracuda VR,the gas-particle hydrodynamics and the erosion of particles on the inner wall and internal components of the spouted bed in the integrated multi-jet swirling spout-fluidized bed(IMSSFB)are studied.Erosion experiments have obtained the characterization of particle erosion on internal components and verified the relevant numerical models.The results show that:the particle distribution within the IMSSFB is uneven due to the cyclonic effect of the axial swirl vane(ASV),resulting in particle erosion for the ASV being concentrated on one side;when the gas reaches the top,too high an erosion gas velocity leads to gas backflow.As the filling height increases,there is a tendency for the erosion position of the particles on the ASV to expand upwards.However,the effect of increasing gas velocity on the erosion position is insignificant.

Collisionless shock acceleration of protons in a plasma slab produced in a gas jet by the collision of two laser-driven hydrodynamic shockwaves

We have recently proposed a new technique of plasma tailoring by laser-driven hydrodynamic shockwaves generated on both sides of a gas jet[Marquès et al.,Phys.Plasmas 28,023103(2021)].In a continuation of this numerical work,we study experimentally the influence of the tailoring on proton acceleration driven by a high-intensity picosecond laser in three cases:without tailoring,by tailoring only the entrance side of the picosecond laser,and by tailoring both sides of the gas jet.Without tailoring,the acceleration is transverse to the laser axis,with a low-energy exponential spectrum,produced by Coulomb explosion.When the front side of the gas jet is tailored,a forward acceleration appears,which is significantly enhanced when both the front and back sides of the plasma are tailored.This forward acceleration produces higher-energy protons,with a peaked spectrum,and is in good agreement with the mechanism of collisionless shock acceleration(CSA).The spatiotemporal evolution of the plasma profile is characterized by optical shadowgraphy of a probe beam.The refraction and absorption of this beam are simulated by post-processing 3D hydrodynamic simulations of the plasma tailoring.Comparison with the experimental results allows estimation of the thickness and near-critical density of the plasma slab produced by tailoring both sides of the gas jet.These parameters are in good agreement with those required for CSA.

Hydrodynamic Cavitation Enhanced SR-Aops Degradation of Organic Pollutants in Water:A Review

SR-AOP(sulfate radical advanced oxidation process)is a novel water treatment method able to eliminate refractory organic pollutants.Hydrodynamic cavitation(HC)is a novel green technology,that can effectively produce strong oxidizing sulfate radicals.This paper presents a comprehensive review of the research advancements in these fields and a critical discussion of the principal factors influencing HC-enhanced SR-AOP and the mechanisms of synergistic degradation.Furthermore,some insights into the industrial application of HC/PS are also provided.Current research shows that this technology is feasible at the laboratory stage,but its application on larger scales requires further understanding and exploration.In this review,some attention is also paid to the design of the hydrodynamic cavitation reactor and the related operating parameters.

Hydrodynamic characteristics and particle tracking of 90° lateral intakes at an inclined river slope

Lateral intakes are common in rivers.The pump effciency and sediment deposition are determined by the local hydrodynamic characteristics and mainstream division width.The hydraulic characteristics of lateral withdrawal from inclined river slopes at different intake elevations should be investigated.Meanwhile,the division width exhibits significant vertical non-uniformity at an inclined river slope,which should be clarified.Hence,a three-dimensional(3-D)hydrodynamic and particle-tracking model was developed with the Open Source Field Operation and Manipulation(Open FOAM),and the model was validated with physical model tests for 90°lateral withdrawal from an inclined side bank.The flow fields,withdrawal sources,and division widths were investigated with different intake bottom elevations,withdrawal discharges,and main channel velocities.This study showed that under inclined side bank conditions,water entered the intake at an oblique angle,causing significant 3-D spiral flows in the intake rather than two-dimensional closed recirculation.A lower withdrawal discharge,a lower bottom elevation of the intake,or a higher main channel velocity could further strengthen this phenomenon.The average division width and turbulent kinetic energy were smaller under inclined side bank conditions than under vertical bank conditions.With a low intake bottom elevation,a low withdrawal discharge,or a high main channel velocity,the sources of lateral withdrawal were in similar ranges near the local inclined bank in the vertical direction.Under inclined slope conditions,sediment deposition near the intake entrance could be reduced,compared to that under vertical slope conditions.The results provide hydrodynamic and sediment references for engineering designs for natural rivers with inclined terrains.

Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

三维Electro-Hydrodynamics方程组光滑解的延拓准则

研究了三维Electro-Hydrodynamics方程组局部光滑解的延拓准则,利用负指标Besov空间中的对数Sobolev不等式和Kato-Ponce交换子估计方法,在Besov空间中获得了只涉及速度场水平分量的最优延拓准则,改进和推广了已有关于Electro-Hydrodynamics方程组正则性准则的部分结论,是Electro-Hydrodynamics方程组正则性理论的有益补充。

Hydrodynamic Simulation of the Pagasitikos Gulf, Greece

Semi-enclosed sea basins have difficulty in recharging their waters due to limited communication with larger water bodies, with understandable consequences for their environmental status. This paper aims at the computational simulation of the hydrodynamic characteristics of the waters of the Pagasitikos Gulf (Greece), which has limited communication and water exchange with the Aegean Sea and is subject to intense environmental pressures The Estuary, Lake & Coastal Ocean 3d hydrodynamic Model (ELCOM 2.2) combined with its later version Aquatic Ecosystem Model-3d (AEM3D) were used for the simulation. The simulation included the topography of the area, the bay’s bottom geometry, atmospheric loadings, tides, the influence of the Coriolis force and boundary conditions. The hydrodynamic behaviour of the bay, water circulation, velocities at the surface and in depth, water recharge and residence time throughout the bay, density variation and other factors were examined to determine the impact of all these on the aquatic ecosystem.

Simulation of Natural Convection Flow with Magneto-Hydrodynamics in a Wavy Top Enclosure with a Semi-Circular Heater

Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approach is used to solve two-dimensional governing mass, momentum and energy-equations for natural convection flow in the presence of a magnetic field on a roof top with semi-circular heater. In the enclosure the horizontal lower wall was heated, the vertical two walls were adiabatic, inside the semi-circular heater, the wavy top wall cooled. The parameters Rayleigh number, Hartmann number and Prandtl number are considered. The effects of the Hartmann number and Rayleigh number on the streamlines, isotherms, velocity profiles and average Nusselt number are examined graphically. The local Nusselt number and the average Nusselt number of the heated portion of the enclosure with the semi-circular heater are presented in this paper. Finally, for the validation of the existing work, the current results are compared with published results and the auspicious agreement is achieved.

Effects of hydrodynamics processes on phosphorus fluxes from sediment in large,shallow Taihu Lake

The turnover of phosphorus （P） in lake sediments, a major cause of eutrophication and subsequent deterioration of water quality, is in need of deep understanding. In this study, effects of resuspension on P release were studied in cylindrical microcosms with Yshape apparatus. The results indicated that there was a positive correlation between flux of suspended substance across sediment-water interface （Fss） and the wind speed, and an increasing Fss during each wind process followed by a steady state. The maximal Fss under fight, moderate, and strong wind conditions were 299.9±41.1,573.4±61.7, and 2093.8±215.7 g/m^2, respectively. However, flux of P across sediment-water interface （Fp） did not follow a similar pattern as Fss responding to wind intensity, which increased and reached the maximum in initial 120 rain for fight wind, then decreased gradually, with maximal flux of 9.4±1.9 mg/m^2. A rapid increase of Fp at the first 30 rain was observed under moderate wind, with maximal flux of 11.2±0.6 mg/m^2. Surprisingly, strong wind caused less Fp than under light and moderate wind conditions with maximal flux of 3.5±0.9 mg/m^2. Fss in water column declined obviously during the sedimentation process after winds, but Fp varied with wind regime. No obvious difference was detected on Fp after 8 h sedimentation process, compared with the initial value, which means little redundant P left in the water column after winds.

Leaching hydrodynamics of weathered elution-deposited rare earth ore

Both porosity ( φ ) and permeability ( k ) of the weathered elution deposited rare earth ores are basic hydrodynamic parameters for RE leaching. The relationship between k and φ of two typical rare earth ores of South China in the packed bed was investigated by measuring the flow ( Q ) under various leaching pressure difference (Δ p ). The experimental results show that the relationship between k and φ is unique, moreover the relationship between Q and Δ p is in accord with the Darcy’s law. The effects of the type of ores, the leaching reagents and its concentration, the granule ore size on the leaching permeability have also been investigated. It is demonstrated that k H (for heavy RE ore, k H=35.98?mm 2)> k M H (for middle heavy RE ore, k M H =28.50?mm 2), whereas k (NH 4NO 3)> k (NH 4Cl)> k [(NH 4) 2SO 4], and the k value increases with increasing leaching reagents concentration and granule ore size( k 0.60～0.75?mm =99.96?mm 2, k 0.125～0.60?mm =11.83?mm 2, k 0.074～0.125?mm =0.84?mm 2). [

Application of CFD Modeling to Hydrodynamics of CycloBio Fluidized Sand Bed in Recirculating Aquaculture Systems

To improve the efficiency of a CycloBio fluidized sand bed(CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics(CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simulations with the granular Eulerian multiphase approach and the RNG k-ε turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O'Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume fraction of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in order to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.

Learning from Fish: Kinematics and Experimental Hydrodynamics for Roboticists

Over the past 20 years, experimental analyses of the biomechanics of locomotion in fishes have generated a number of key findings that are relevant to the construction of biomimetic fish robots. In this paper, we present 16 results from recent experimental research on the mechanics, kinematics, fluid dynamics, and control of fish locomotion that summarize recent work on fish biomechanics. The findings and principles that have emerged from biomechanical studies of fish locomotion provide important insights into the functional design of fishes and suggest specific design features relevant to construction of robotic fish-inspired vehicles that underlie the high locomotor performance exhibited by fishes.

Hydrodynamics and Mass Transfer in a Modified Three-phase Airlift Loop Reactor

A modified internal-loop airlif reactor （MIALR） with a continuous slurry phase was studied to investigate the local hydrodynamic characteristics, including gas holdup, bubble size, bubble rise velocity and local mass transfer properties. Based on the analysis of geometrical construction and fluid properties of gas and slurry, MIALR was divided into six flow regions. In these flow regions, the local hydrodynamic characteristics were investigated over a wide range of operating variables. Furthermore, a new method was developed to measure the dissolved oxygen concentration. The volumetric mass-transfer coefficient in six flow regions was also calculated for comparison.

Experimental and numerical investigations of scale-up effects on the hydrodynamics of slurry bubble columns

Experiments and simulations were conducted for bubble columns with diameter of 0.2 m(180 mm i.d.), 0.5 m(476 mm i.d.) and 0.8 m(760 mm i.d.) at high superficial gas velocities(0.12–0.62 m·s-1) and high solid concentrations(0–30 vol%). Radial profiles of time-averaged gas holdup, axial liquid velocity, and turbulent kinetic energy were measured by using in-house developed conductivity probes and Pavlov tubes. Effects of column diameter, superficial gas velocity, and solid concentration were investigated in a wide range of operating conditions. Experimental results indicated that the average gas holdup remarkably increases with superficial gas velocity, and the radial profiles of investigated flow properties become steeper at high superficial gas velocities. The axial liquid velocities significantly increase with the growth of the column size, whereas the gas holdup was slightly affected. The presence of solid in bubble columns would inhibit the breakage of bubbles, which results in an increase in bubble rise velocity and a decrease in gas holdup, but time-averaged axial liquid velocities remain almost the same as that of the hollow column. Furthermore, a 2-D axisymmetric k–ε model was used to simulate heterogeneous bubbly flow using commercial code FLUENT 6.2. The lateral lift force and the turbulent diffusion force were introduced for the determination of gas holdup profiles and the effects of solid concentration were considered as the variation of average bubble diameter in the model. Results predicted by the CFD simulation showed good agreement with experimental data.

Investigation of the hydrodynamics of slug flow in airlift pumps

A slug flow model considering the dispersed bubbles entrained from the tail of Taylor bubble(TB) and recoalesced with the successive TB was proposed. Experiment was conducted to test the validity of this model by using a high-speed camcorder and particle image velocimetry(PIV). It was found that the model was valid for predicting the characteristics of slug flow in airlift pump within average error of 14%. Moreover, large pipe diameter was found to accelerate the rise velocity of TB and decreases void fraction in liquid slug by a small margin.

Research on Hydrodynamics Model Test for Deepsea Open-Framed Remotely Operated Vehicle

This paper presents the features of newly designed hydrodynamics test for the scaled model of 4500 m deepsea open-framed remotely operated vehicle （ROV）, which is being researched and developed by Shanghai Jiao Tong University. Accurate hydrodynamics coefficients measurement and spatial modeling of ROV are significant for the maneuverability and control algorithm. The scaled model of ROV was constructed by 1：1.6. Hydrodynamics coefficients were measured through VPMM and LAHPMM towing test. And dynamics model was derived as a set of equations, describing nonlinear and coupled 5-DOF spatial motions. Rotation control motion was simulated to verify spatial model proposed. Research and application of hydrodynamics coefficients are expected to enable ROV to overcome uncertainty and disturbances of deepsea environment, and accomplish some more challengeable and practical missions.

THE WELL-POSEDNESS AND ASYMPTOTICS OF MULTI-DIMENSIONAL QUANTUM HYDRODYNAMICS

The multi-dimensional quantum hydrodynamic equations for charge transport in ultra-small electronic devices like semiconductors, where quantum effects （like particle tunnelling through potential barriers and built-up in quantum wells） take place, is considered in the present paper, and the recent progress on well-posedness, stability analysis, and small scaling limits are reviewed.

Feedback between tidal hydrodynamics and morphological changes induced by natural process and human interventions in a wave-dominated tidal inlet: Xiaohai, Hainan, China

The feedback between morphological evolution and tidal hydrodynamics in a wave-dominated tidal inlet, Xiaohai, China is investigated through data analysis and numerical model experiments. Historically, Xiaohai Inlet had two openings, located at the north and south of Neizhi Island （a rocky outcrop）, respectively. The evolution of Xiaohai Inlet was dominated by the natural process before 1972. In addition to the natural process, human interventions, including the closure of the north opening, 50% of freshwater reduction, and increase of land reclamation, have altered tidal hydrodynamics and morphological evolution since 1972. A series of numerical model simulations were conducted to investigate the influence of morphological changes on the hydrodynamics and the influence of human activities on the inlet evolution. The natural process has caused narrowing and shoaling of the inlet throat, development of the flood-tidal delta, and shoaling of the tidal channel inside the lagoon. Human interventions have accelerated these changes. Consequently, the tidal propagation from the offshore into the lagoon has been impeded and the tidal energy has been dissipated substantially. Tidal current has changed from ebb-dominant to flood-dominant in most parts of the inlet system whereas the inlet throat has remained as ebb-dominant, the tidal prism has decreased consistently, and sediment has continued to deposit inside the inlet. As a result, the changes of morphology, hydrodynamics, and sediment transport show a positive feedback. The human interventions have had both advantageous and adverse influences on the stability of the inlet. The closure of the North Opening has decreased the longshore sediment input to the inlet, and increased the tidal prism, ebb velocity, and sediment transport in the south opening, thus enhancing the inlet＇s stability. However, reducing the river discharge and landfill of the tidal flats has resulted in a decrease of the tidal prism, the ebb velocity, and the ability to export sediment, thus having the tendency to deteriorate the inlet＇s stability. A stability analysis based on a closure curve methodology has shown that Xiaohai Inlet is in a state of dynamic equilibrium at present.

Side Wall Effects on the Hydrodynamics of a Floating Body by ImageGreen Function Based on TEBEM

A novel numerical model based on the image Green function and first-order Taylor expansion boundary element method(TEBEM), which can improve the accuracy of the hydrodynamic simulation for the non-smooth body, was developed to calculate the side wall effects on first-order motion responses and second-order drift loads upon offshore structures in the wave tank. This model was confirmed by comparing it to the results from experiments on hydrodynamic coefficients, namely the first-order motion response and second-order drift load upon a hemisphere, prolate spheroid, and box-shaped barge in the wave tank. Then,the hydrodynamics of the KVLCC2 model were also calculated in two wave tanks with different widths. It was concluded that this model can predict the hydrodynamics for offshore structures effectively, and the side wall has a significant impact on the firstorder quantities and second-order drift loads, which satisfied the resonant rule.