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A high-speed debris flow sliding into a reservoir can cause a huge disaster. Consequently, predicting landslide movement accurately and its potential interaction with water is crucial. This paper developed a computational model based on a two–layer two–phase material point method (MPM) to simulate surge waves generated by granular landslides on an erodible slope. By comparing granular landslide on a rigid and erodible slope, the effect of the slope erodibility on the process of landslide movement and the waves generated is investigated. The model takes full account of the large deformations, fluidisation and settlement of granular material in soil–water interactions. The numerical model is validated by comparing the simulated results with experimental data. The influences of internal friction angle, density, elastic modulus, Poisson ratio and dilatancy angle on wave height are also studied. The validated model was then used to investigate the surge waves generated by dry and saturated granules sliding along a rigid and erodible slope. The results show that both the erodible slope and saturated granular slide can increase the first wave crest height generated by the landslide.

The mechanism of the flow resistance in open channels and pipelines is of vital importance for various critical issues related to the water flow. The Nikurade’s method of calculating the friction factor is not applicable in some cases. It is necessary to consider the influence of the vortex volume surrounding the vegetation and to study the hydrodynamic characteristics of the vegetated channels. This paper analyzes the variation of the vortices created by the surface roughness of different types and different sizes and proposes new definitions of the hydraulic radius and the equivalent roughness height. With consideration of the skin friction and the form drag, on the basis of the force balance equation, a novel calculation method is used for the friction factor, and this method is verified by experimental data. The hydrodynamic mechanism of the flow resistance revealed in this study may serve as a theoretical basis for hydraulic engineers to calculate the friction factor.

Piles with enlarged base have been widely employed in the civil and coastal engineering due to its high resistance to uplift. Many researchers have investigated the bearing capacity of enlarged base piles in case of small strains, but the investigations of enlarged base piles with variable geometries and large deformations are very limited. In this work, Material Point Method (MPM) is adopted to investigate the uplifting behavior of enlarged base piles with variable geometries and large deformations. As a continuum-based particle method, the MPM is well-suited to model the dynamic large deformation problems, for which the conventional Finite Element Method (FEM) is limited due to the mesh distortion. Centrifuge uplift tests of enlarged base piles in dense and loose sand are simulated using MPM and the calculated results are compared with the corresponding experimental data. The influence of various parameters such as bell angle, shaft/bell diameter ratio and the contact friction angle between the soil and pile, on the uplift capacity in sand have been investigated.

Due to the complicated interactions between the liquid phase and solid particles, it is important to adequately simulate the components themselves in a non-Newtonian solid–liquid flow with a free surface. In this work, a hybrid computational framework is presented to simulate the non-Newtonian free-surface flow of the liquid-grain mixture by coupling the Moving Particle Semi-implicit (MPS) method and the Discrete Element Method (DEM). The DEM governs the motion of the solid particles, while the MPS is extended to model the non-Newtonian rheology and free surfaces. The robustness and the correctness of the proposed method were illustrated by several numerical examples involving non-Newtonian free surface flows with solid particles. The simulated results were in good agreement with analytical solutions or available experimental data in the literatures.

Landslide generated tsunami waves can trigger debris flows or floods which may lead to serious damage to civil structures and endanger life. Therefore, it is important to deeply understand such problems for disaster prevention and mitigation. In this work, a three dimensional multiple-relaxation-time Lattice-Boltzmann model (LBM) is developed for numerically investigating the landslide movement, landslide-water interaction, and water-wave generation and propagation process. We select the LBM based simulation algorithm due to its overall computational efficiency and its capability to deal with complex geometries and topologies. Both aerial and submerged rigid landslide-generated tsunami waves are simulated. The obtained numerical solutions are compared with corresponding experimental data in the literature and the results are in good agreement. It shows that the proposed LBM method is potentially an alternative tool for modeling landslide-generated tsunami waves.

In the present study, an analytical concept model is built, using a two-phase model for the sediment transport in a pure acceleration-skewed oscillatory sheet flow. The analytical model is based on the asymmetric wave theory, the irregular boundary layer theory and the exponential concentration distribution theory, to be used for analyzing the phase lag and the boundary layer development related to the acceleration skewness. The two-phase model is applied for the calculations of the instantaneous erosion depth, the sediment flux, the boundary layer thickness and the sediment transport rate, as well as the differences between the positive acceleration stage and the negative acceleration stage caused by the acceleration skewness, as very important in the net current and sediment transport. The effects of the sediment diameter and the phase lag are explained by a comparison with the instantaneous type empirical formula, as is closely related to the acceleration skewness. With the analytical concept model and the two-phase model, the generation of the net sediment transport in the pure acceleration-skewed flows is clearly explained. The phase lag effect is important for the instantaneous sediment transport in the pure acceleration-skewed flow, whereas the boundary layer development difference between the positive acceleration stage and the negative acceleration stage plays a major role in the determination of the net sediment transport.

Velocity-skewed oscillatory sheet flow transport is studied by an approximate model for instantaneous sediment transport resulting from exponential profiles of sediment concentration and velocity over a mobile bed. The phase lag effect, and asymmetry in wave friction factor, oscillatory flow orbital amplitude, roughness height, bed shear stress and wave boundary layer thickness are modelled so that the net boundary layer stream of pure velocity-skewed oscillatory flow can be obtained. The proposed model is found consistent with the previous classical formulas, and qualitatively refines a series of exponents of velocity power function for the approximation of instantaneous sediment transport rate under different flow conditions. The sediment fluxes can be well predicted with accuracy as that of a two-phase numerical model. The net boundary layer stream and sediment transport rates are also well predicted, especially the negative net stream and rates with large phase residual. The phase residual is shown a useful but insufficient factor in the net sediment transport in pure velocity-skewed flows. In addition, the net boundary layer stream resulting from velocity-skewed wave boundary layer development difference between onshore and offshore flow durations is an essential factor as well.

With the rapid development of microelectronics, computer, sensor and communication technology, the measuring and controlling of hydraulic structures has gradually realized automation and intelligent information collection will be more and more perfect. As a commonly used hydraulic structure, sluice gate needs to be combined with modern technology to provide basic data and control flow in more scientific and efficient ways. Different discharge methods are available to determine discharge under sluice gates. The present paper designs a new float type float and proposes a way to measure the discharge through the gate. This paper compares the new equation of (Q) with (e/H) under free flow condition with proposed equations by other researchers. The results shows that other equations fail to accurately determine the flow rate for the cases of free flow, while employing the new proposed equations can result in more accurate discharge estimation within the given ranges of the experimental study. The development of velocity profile under sluice gate is examined, and the effects of shear stress are studied. The new method can be used to predict the performance of sluice gates with different sizes under free -flow situations. These results may attract and guide numerical modelers of flow. A free flow automation measuring and controlling system based on single chip microcomputer and sensor can be designed, which will be application of computer, sensors and other modern technology. Thus realizing scientific water management, optimal allocation and accurate measurement of water resources.

Ordinary cement-based materials exhibit strong hydrophilicity and brittleness after hardening, which is very detrimental to their durability and service life. In this study, a low-cost and nontoxic silane-based hydrophobic agent and waste tire rubber particles are used to make integrally hydrophobic self-compacting rubberized mortar (HSCRM). The fluidity of the HSCRM is enhanced and its setting time is prolonged with increasing hydrophobic agent content. When the content of the hydrophobic agent is 2%, the HSCRM exhibits integral overhydrophobicity, with the static contact angle (CA) on the surface larger than 120°. In addition, compared with the self-compacting mortar (SCM), the immersion water absorption and capillary water absorption of HSCRM decrease by 72.1% and 89.3%, respectively, while the corrosion resistance of the HSCRM is significantly enhanced and its surface deicing process is much easier. Moreover, the 28 d flexural strength, compressive strength and splitting tensile strength of the HSCRM are 18.9%, 32.3%, and 17.2% lower than those of the SCM, respectively, but the toughness and ductility of the HSCRM are significantly improved.

This paper presents the simulation of tsunamis due to rigid and deformable landslides with consideration of submerged conditions by using particle methods. The smoothed particle hydrodynamics (SPH), as a particle based method, is for solving problems of fast moving boundaries in the field of continuum mechanics. Other particle based methods, like the discrete element method (DEM), are suitable for modeling the displacement and the collision related to the rigid landslides. In the present work, we use the SPH and the DEM to simulate tsunamis generated by rigid and deformable landslides with consideration of submerged conditions. The viscous free-surface flows are solved by a weakly compressible SPH and the displacement and the rotation of the rigid body slides are calculated using a multi-sphere DEM allowing for modeling solids of arbitrarily complex shapes. The fluid-solid interactions are simulated by coupling the SPH and the DEM. A rheology model combining the Papanastasiou and the Herschel-Bulkley models is applied to represent the viscoplastic behavior of the non-Newtonian flow in the submarine deformable landslide cases. Submarine landslide tsunamis due to rigid and deformable landslides are both simulated as typical landslide cases in this investigation. Our simulated results and the previous experimental results in the literatures are in good agreement, which shows that the proposed particle based methods are capable of modeling the submarine landslide tsunamis.

In this paper, the characteristics of sediment yield on slopes under different rainfall intensities (30, 50, and 70 mm/h) are studied through rainfall simulation test. The results show that the runoff yield time decreases with the increase of rainfall intensity, and the runoff and sediment yield fluctuate more significantly. The variation of the sediment yield with rainfall duration can be described by a power function. The erosion morphology of slope is mainly characterized by splash and sheet erosion. The area with severe erosion is 0.158 m2, accounting for 26.3% of the slope area. Generally speaking, with the increase of rainfall intensity, the disturbance effect on runoff and sediment yield is enhanced, and the degree of erosion damage on slope is increased.

Embankments are usually constructed along rivers as a defense structure against flooding. Overtopping failure can cause devastating and fatal consequences to life and property of surrounding areas. This motivates researchers to study the formation, propagation, and destructive consequences of such hazards in risk analysis of hydraulic engineering. This paper reports a numerical simulation of failure processes in homogeneous embankments due to flow overtopping. The employed numerical approach is based on a double-point two-phase material point method (MPM) considering water&ndash, soil interaction and seepage effects. The simulated results are compared to available laboratory experiments in the literature. It was shown that the proposed method can predict the overtopping failure process of embankments with good accuracy. Furthermore, the effects of the cohesion, internal fiction angle, initial porosity, and maximum porosity of soil on the embankment failure are investigated.

Hydraulic engineers often divide a flow region into subregions to simplify calculations. However, the implementation of flow divisibility remains an open issue and has not yet been implemented as a fully developed mathematical tool for modeling complex channel flows independently of experimental verification. This paper addresses whether a three-dimensional flow is physically divisible, meaning that division lines with zero Reynolds shear stress exist. An intensive laboratory investigation was conducted to carefully measure the time-averaged velocity in a rectangular open channel flow using a laser Doppler anemometry system. Two innovative methods are employed to determine the locations of division lines based on the measured velocity profile. The results clearly reveal that lines with zero total shear stress are discernible, indicating that the flow is physically divisible. Moreover, the experimental data were employed to test previously proposed methods of calculating division lines, and the results show that Yang and Lim’s method is the most reasonable predictor.

A FEM-DEM approach was applied to investigate progressive rupture of concrete structures due to dynamic load including earthquakes. In the proposed method, the finite element method (FEM) designed for modelling stressed and deformed solids has been combined with the motion tracking capability of discrete element method (DEM). A fracture model combining single and smeared crack model is used in our simulation. The FEM-DEM method was used to simulate both the intact concrete behavior and the development of fractures in the indirect tensile test. The simulation results identify the failure mechanisms and validate the nature of tensile crack initiation and propagation in concrete disk. In particular, a comprehensive study on the seismic rupture of the Koyna dam during earthquakes is performed using the proposed method. It is shown that the proposed method can predicate the formation and propagation of cracks in concrete dam due to earthquakes.

The effect of wall normal velocity on velocity distribution in unsteady flow has been investigated. We established a modified log-law model by adding the wake-term by Coles and deviation term together to depict the velocity deviation caused from classic log-low model. An empirical formula for deviation-correction factor α has been determined based on the present experimental data, and it yields a good agreement with other published experimental data. Experimental measurements of velocity distributions in unsteady open channel flows have been performed to prove this model.The cause of this addition was discussed and explained, and the theoretical velocity images from the improved model have been compared with the present data, they are well correlated.

Dams breach by overtopping is a serious natural disaster. Numerical simulation, as a efficient research method, is widely used to study the failure mechanism and predict the destroyed process of earth dams. Traditional numerical methods such as the finite element method (FEM) only provide the capacity of small deformation analyses due to mesh distortion. The Material Point Method (MPM), a mesh-free method, has been worked well for large deformation analyses. In this paper, a double-point MPM is introduced to analysis the failure process of earth-filled dams due to overtopping. Finally, it shows that the MPM predicts the flow propagation, the development of breach cross section and breach longitudinal profile well. Moreover, MPM provides an alternative method for the risk assessment of dam breach.

A hybrid scheme coupling the discrete element method (DEM) with the computational fluid dynamics (CFD) is developed to model solid-liquid flows. Instead of solving the pressure Poisson equation, we use the compressible volume-averaged continuity and momentum equations with an isothermal stiff equation of state for the liquid phase in our CFD scheme. The motion of the solid phase is obtained by using the DEM, in which the particle-particle and particle-wall interactions are modelled by using the theoretical contact mechanics. The two phases are coupled through the Newton's third law of motion. To verify the proposed method, the sedimentation of a single spherical particle is simulated in water, and the results are compared with experimental results reported in the literature. In addition, the drafting, kissing, and tumbling (DKT) phenomenon between two particles in a liquid is modelled and reasonable results are obtained. Finally, the numerical simulation of the density-driven segregation of a binary particulate suspension involving 10 000 particles in a closed container is conducted to show that the presented method is potentially powerful to simulate real particulate flows with large number of moving particles.

We applied the discrete element method (DEM) to analyze the normal impact properties of elastoplastic spherical particles. DEM simulation of impact between two identical elastoplastic spheres is carried out to validate the proposed model. The numerical results show well agreement with the FEM solution. Based on this model, the effects of impact parameters such as velocity, yield strength, elastic modulus, Poissons ratio, and mass density, on the loss factor in impact process, are then analyzed.

Thanks to the recent development of tools such as CUDA and OpenCL it has become possible to fully utilize Graphical Processing Units (GPUs) for scientific computing. OpenCL promises huge savings in parallel code development and optimization efforts due to it is not restricted to a specific architecture. We have developed an OpenCL-based acceleration framework on GPU for numerical simulations of incompressible flows using incompressible Smoothed Particle Hydrodynamics (ISPH). In order to assess the performance of the GPU implementation presented in the present work, a comparison was made against the implementation of the same ISPH in CPU using OpenCL.

This work presents a three-dimensional two-way coupled method to simulate moving solids in viscous free-surface flows. The fluid flows are solved by weakly compressible smoothed particle hydrodynamics (SPH) and the displacement and rotation of the solids are calculated using the multisphere discrete element method (DEM) allowing for the contact mechanics theories to be used in arbitrarily shaped solids. The fluid and the solid phases are coupled through Newton’s third law of motion. The proposed method does not require a computational mesh, nor does it rely on empirical models to couple the fluid and solid phases. To verify the numerical model, the floating and sinking processes of a rectangular block in a water tank are simulated, and the numerical results are compared with experimental results reported in published literatures. The results indicate that the method presented in this paper is accurate and is capable of modelling fluid-solid interactions with a free-surface.

We report the development of a new analytical model similar to the Reynolds-averaged Navier-Stokes equations to determine the distribution of streamwise velocity by considering the bursting phenomenon. It is found that, in two-dimensional (2D) flows, the underlying mechanism of the wake law in 2D uniform flow is actually a result of up/down events. A special experiment was conducted to examine the newly derived analytical model, and good agreement is achieved between the experimental data in the inner region and the model’s prediction. The obtained experimental data were also used to examine the DML-Law (dip-modified-log-law), MLW-Law (modified-log-wake law), and CML-Law (Cole’s wake law), and the agreement is not very satisfactory in the outer region.

We present a numerical method combining the smoothed particle hydrodynamics (SPH) and discrete element method (DEM) to model liquid flows in the presence of solid particles. This approach does not require a computational mesh, nor does it rely on empirical models to couple the liquid and solid phases. In the present method, the SPH is applied to simulate the liquid flows, and the DEM together with interaction laws based on the theoretical contact mechanics is introduced into the SPH method to calculate the effects of contact between solid particles and between solid particles and walls. The introduced DEM model is verified by experimental analyses for the collapse of six solid cylinder layers. The proposed DEM–SPH model is then applied to simulate the free falling of a rigid sphere in water with a free surface.

A numerical model coupling the discrete element method (DEM) and the computational fluid dynamics (CFD) was presented and applied to simulate particle flocculation and sedimentation processes. The volume-averaged continuity and momentum equations are solved for fluid motions, while the particle motion is modeled by the DEM with considering the inter-particle interactions based on mechanics of contact. The van der Waals force induced cohesive attractions between particles were taken into account in our study. The predicated results demonstrated that the proposed method is capable of simulating the particle sedimentation and flocculation process.

Sluice gates are commonly used in canals for control and measurement of the flow. The discharge under sluice gates can be determined through different discharge methods. The present study proposed a new equation to accurately predict the discharge through floating type sluice gate by reading the depth of water at upstream of the gate and it reveals relationship between the gate opening and water depth. It also derived a theoretical equation for variations of sluice gate discharge coefficient under free flow condition. Effects of factors on discharge coefficient were investigated. This new model can be used to predict the performance of sluice gates with different sizes under free-flow situations.

The dynamic response of a free–free flexible beam floating in an unbounded water domain under the effect of moving loads is numerically analyzed. The water is assumed compressible and inviscid. The surface disturbance satisfies a linear free surface wave condition and an undisturbed condition at infinity. In the present work, a finite element procedure was developed directly in time domain and implemented to solve the two-dimensional problem of the transient behavior of an elastic beam floating on the surface of finite deep water under the passage of a moving force with uniform speed. The presented data demonstrates the applicability of the proposed mathematical model and numerical approach. The influences on the dynamic responses of floating beam of some factors were studied.

Water waves generated by landslides have been of interest to ocean and coastal engineers, as well as to dam engineers. The present study uses a meshless and pure Lagrangian method known as smoothed particle hydrodynamics (SPH) to simulate nonlinear water waves due to landslides, with the aim of an accurate numerical prediction of the generation and propagation of such water waves. Validation is carried out by comparison between the computed prediction and experimental data of water waves generated by a two-dimensional triangular rigid body sliding into water. The calculated results show that the simulated water waves agree well with those observed in the experiment confirming the effectiveness and the accuracy of the proposed scheme.

The damage caused by surge waves generated in water bodies by flow-like landslides can be very high in terms of human lives and economic losses. The complicated phenomena occurred in this highly unsteady process are difficult to model because three interacting phases: air, water and sediment are involved. The problem therefore is challenging since the effects of non-Newtonian fluid describing the rheology of the flow-like landslides, multi-phase flow and free surface have to be included in the simulation. In this work, the commercial computational fluid dynamics (CFD) package FLUENT is used to model the surge waves due to flow-like landslides. The comparison between the numerical results and experimental data reported in the literature confirms the accuracy of the method., {"references":["Quecedo M, Pastor M, Herreros MI. Numerical modelling of impulse\nwave generated by fast landslides. International journal for numerical\nmethods in engineering 2004; 12: 1633-1656.","Jakob M, Hungr O (eds). Debris-flow Hazard and Related Phenomena.\nSpringer: Berlin, 2005; 739.","Pastor M, Quecedo M, Fern´andez Merodo JA, Herreros MI, Gonz´alez\nE, Mira P. Modelling tailing dams and mine waste dumps failures.\nGeotechnique 2002; LII(8):579–592.","Huang X, Garca M. A perturbation solution for Bingham-plastic mud\nflows. ASCE Journal of Hydraulic Engineering 1997; 120:1350-1363.","Jiang L, LeBlond PH. Numerical modeling of an underwater Bingham\nplastic mudslide and the waves which it generates. Journal of Geophysical\nResearch 1993; 98 :10303–10317.","Trunk FJ, Dent JD, Lang TE. Computer modeling of large rock slides:\nJournal of Geotechnical Engineering 1986; 112 (3):348–360.","Mei CC, Liu KF. Approximate equations for the slow spreadingof a thin\nsheet of Bingham plastic fluid. Physics of Fluids 1990; 2:30–36.","Savage SB, Hutter K. The motion of a finite mass of granular material\ndown a rough incline. J. Fluid Mech. 1989; 199:177-215.","Walder JS, Watts P, Sorensen OE and Janssen K. Tsunami generated by\nsubaerial mass flows. J. Geophysical Res. 2001; 108: 22-36.\n[10] Fritz HM, Hager WH and Minor HE. Near Field Characteristic of\nLandslide Generated Impulse Waves, J. Waterway, Port, Coast, and\nOcean Engrg. 2004; 130:287-302.\n[11] Liu, PLF, Wu TR, Raichlen F, Synolakis CE and Borrero JC. Runup and\nrundown generated by three-dimensional sliding masses. J. Fluid Mech.\n2005; 536:107-144.\n[12] Enet F and Grilli ST. Experimental Study of Tsunami Generation by\nThree-dimensional Rigid Underwater Landslides, J. Waterway Port\nCoastal and Ocean Engng. 2007; 6:442-454.\n[13] Heinrich P. Nonlinear water wave generated by submarine and aerial\nlandslides. J. Waterway, Port, Coastal and Ocean Engineering\n1992;118(3): 249-266.\n[14] Monaghan JJ, Kos A, Issa N. Fluid motion generated by impact. Journal\nof the Waterway, Port, Coastal, and Ocean Engineering (ASCE) 2003;\n129:250–259.\n[15] Qiu LC. Two-Dimensional SPH Simulations of Landslide-Generated\nWater Waves. J. Hydr. Engrg. (ASCE) 2008; 5(134): 668-671.\n[16] Fluent. Fluent 6.3 user's guide. Lebanon: New Hampshire (USA) Fluent\nInc.;2006.\n[17] Rzadkeiwicz SA, Mariotti C, Heinrich P. Numerical simulation of\nsubmarine landslides and their hydraulic effects. Journal of Waterway,\nPort, Coastal, and Ocean Engineering 1997; 123: 149-157."]}

The dynamic response of a floating platform under the effects of impulsive and moving loads is of concern in various areas of engineering technology, such as floating airports, floating bridges and buoyant tunnels, among others. In the present work, the floating platform is simplified as a flexible beam floating in an infinite water domain. The water is assumed to be compressible and inviscid, whose governing equation is formulated in terms of the hydrodynamic pressure variable. The surface disturbance satisfies a linear free-surface wave condition and a radiation wave condition at an artificially truncated boundary. A time-domain finite element model is developed to analyze this fluid–structure interactive dynamical system, which exhibits strong coupling between the system’s components. The numerical results are compared with the experimental and numerical ones. The results of comparison confirmed the validity of the proposed approach. The influences on the dynamic responses of floating beam of some factors were studied.

A two-dimensional coupling model of the discrete element method (DEM) and the lattice Boltzmann method (LBM) was used to study the fluid flow through porous media. The fluid flow was modeled at a mesoscale level by using the LBM. The particle motion was modeled at microscale level by means of the DEM. The interfacial interaction between the fluid and the solids is resolved by an implicit immersed boundary method (IBM). The proposed method has validated by comparing the numerical results with theoretic solutions in the literature. It demonstrates the ability of the proposed method to simulate fluid flows through complex porous media.