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Abstract: In this paper, several widely used material models for plain concrete under dynamic loading, especially the Concrete Damage model and the Elastic–Plastic Hydrodynamic model are evaluated so as to determine an appropriate material model for engineered cementitious composite (ECC) materials under dynamic loading. The effects of size effect, strain rate effect and the specific equation of state on the dynamic material behaviour are investigated using numerical modelling method. A material model which is appropriate to simulate the dynamic behaviour of ECC materials is established based on the Concrete Damage model. The proposed material model is validated via numerical simulation of the impact process of a hybrid-fibre ECC slab struck by a high-velocity projectile. Advantages and limitations of other material models for dynamic behaviours of ECC materials are also compared and commented in this paper. [Copyright &y& Elsevier]

Abstract: Snow cover is a common and relatively stable land cover condition in winter for cold north regions in China. Snow cover has significant effects on water and heat transfers in frozen soil; it needs to be considered in the study of frozen soil water–heat coupled movements. On the basis of previous research results and physical process analysis of water and heat movements in snow cover and soil, a snow cover–soil union water–heat coupled movements model is established in this paper. The numerical simulation was conducted by using a finite difference method. The results indicate that the simulated values have a similar trend to the measured values and the numerical simulation had big relative errors. However, the average absolute errors of the total and liquid moisture content in frozen soil were all less than 4%, and that of the frozen soil temperature was 1.37 °C. The errors of the numerical simulation were still within the acceptable range. Thus, the snow cover–soil union water–heat coupled movement model constructed in this paper is rational. [Copyright &y& Elsevier]

Abstract: This paper presents a 1D time-domain model for an oscillating water column (OWC) based on previous works on trapped air cavities for marine vehicles. The paper describes the coupling between the hydrodynamic and the thermodynamic forces for an OWC with an orifice. The model enables to obtain the water elevation and pressure variation inside the chamber in the time-domain for regular and irregular waves. The numerical predictions are compared with experimental data performed on a model scale OWC. [Copyright &y& Elsevier]

Summary: The rapid economic development has caused heavy pollution in the Pearl River Delta Region (PRDR) and neighboring regions. In order to investigate the polluted characteristics, a coupled modelling approach has been deployed and the study area in the Pear River Delta is divided into two modelling systems: a river network that is simulated by a 1D hydrodynamic and water quality model, and an estuary that is modelled by a 3D model. The 1D river network model is coupled with the 3D estuary model based on the mass conservation criteria. The hydrodynamic (HD) model is based on 1D hydrostatic shallow water equations, and is solved by the Alternating Direction Implicit Approach. The water quality (WQ) model component is based on advection–diffusion equations. Some physical and bio-chemical processes are included in the WQ model to address the water pollution problems by different pollution substances, in particular, to the chemical oxygen demand (COD). The water quality data of the main rivers from 2004 to 2007 were collected, processed and evaluated. Because no detailed water quality data in the river is available, the COD source pollution intensity in the water quality model is taking the pollutant load from the confluence of the main five outlets of the Pearl River Estuary (PRE) for 1996–2007 as surrogate. The results show that the pollutants from the PRDR have a large impact on the quality of the Hong Kong seawater and much more serious in the wet season with high river discharge. An insight of the flow and transportation mechanism in the river and estuary system has been obtained through the paper, and a reliable basis to control water pollution of the Pearl River Delta is provided in this paper. [Copyright &y& Elsevier]

Abstract: In this paper, we discuss the incorporation of dynamic subgrid scale (SGS) models in the lattice-Boltzmann method (LBM) for large-eddy simulation (LES) of turbulent flows. The use of a dynamic procedure, which involves sampling or test-filtering of super-grid turbulence dynamics and subsequent use of scale-invariance for two levels, circumvents the need for empiricism in determining the magnitude of the model coefficient of the SGS models. We employ the multiple relaxation times (MRT) formulation of LBM with a forcing term, which has improved physical fidelity and numerical stability achieved by proper separation of relaxation time scales of hydrodynamic and non-hydrodynamic modes, for simulation of the grid-filtered dynamics of large-eddies. The dynamic procedure is illustrated for use with the common Smagorinsky eddy-viscosity SGS model, and incorporated in the LBM kinetic approach through effective relaxation time scales. The strain rate tensor in the SGS model is locally computed by means of non-equilibrium moments of the MRT-LBM. We also discuss proper sampling techniques or test-filters that facilitate implementation of dynamic models in the LBM. For accommodating variable resolutions, we employ conservative, locally refined grids in this framework. As examples, we consider the canonical anisotropic and inhomogeneous turbulent flow problem, i.e. fully-developed turbulent channel flow at two different shear Reynolds numbers of 180 and 395. The approach is able to automatically and self-consistently compute the values of the Smagorinsky coefficient, . In particular, the computed value in the outer or bulk flow region, where turbulence is generally more isotropic, is about 0.155 (or the model coefficient ) which is in good agreement with prior data. It is also shown that the model coefficient becomes smaller and approaches towards zero near walls, reflecting the dampening of turbulent length scales near walls. The computed turbulence statistics at these Reynolds numbers are also in good agreement with prior data. The paper also discusses a procedure for incorporation of more general scale-similarity based SGS stress models. [Copyright &y& Elsevier]

Abstract: Spout–fluid beds find a widespread application in the process industry for efficient contacting of large particles with a gas. However, detailed understanding of the complex behavior of these systems is lacking, which leads to significant scale-up problems in industry. In this paper we report results of a combined experimental and simulation study on the various regimes, which can be encountered during spout–fluid bed operation. A regime map for a 3D spout–fluid bed was composed employing spectral analysis of pressure drop fluctuations and fast video recordings. In addition 3D Euler–Lagrange computations were performed to assess the capability of the model to reproduce the experimentally observed flow regimes. The influence of the drag closure on the model results was assessed and the influence of the computational grid was studied using a new method for the implementation of the two-way coupling, which is proposed in this paper. For most regimes our model is able to predict the appropriate regime. The frequency, at which the largest power is found, is overpredicted by the model. Contrary to the experimental observations, our model did not predict any large slugs in the slugging bed regime. The remaining differences between the simulated and experimentally observed bed behavior is most likely related to the representation of the effective fluid–particle interaction in our model, which relies on local spatial homogeneity. [Copyright &y& Elsevier]

Abstract: The lower urinary tract is one of the most complex biological systems of the human body as it involved hydrodynamic properties of urine and muscle. Moreover, its complexity is increased to be managed by voluntary and involuntary neural systems. In this paper, a mathematical model of the lower urinary tract it is proposed as a preliminary study to better understand its functioning. Furthermore, another goal of that mathematical model proposal is to provide a basis for developing artificial control systems. Lower urinary tract is comprised of two interacting systems: the mechanical system and the neural regulator. The latter has the function of controlling the mechanical system to perform the voiding process. The results of the tests reproduce experimental data with high degree of accuracy. Also, these results indicate that simulations not only with healthy patients but also of patients with dysfunctions with neurological etiology present urodynamic curves very similar to those obtained in clinical studies. [Copyright &y& Elsevier]

Abstract: A Liquefied Natural Gas (LNG) tanker will encounter many hazards during its operations and some of them will have high risk levels such as grounding and collision in regions of population concentrations in restricted water. The accident of LNG ships in grounding was reported in narrow channel due to manoeuvring difficulties derived from ship–bank interaction. This paper examines manoeuvring performance of a LNG tanker hull form, which was modified to be fitted by fins while taking into account the ship bank interaction effects. A series of model experiments were conducted in order to measure the hull hydrodynamic forces/moments and ship–bank interaction forces/moments using a series of captive model tests. A time domain simulation program including ship steering autopilot has been developed to study the manoeuvring trajectories for full loading condition. The results of simulations show that the ship–bank interaction effects, fitting fins and enlarging rudder size have significant influence on the manoeuvring capability of the LNG ship in restricted water. [Copyright &y& Elsevier]

Abstract: In solid metal forming processes, such as forging, large distortions in the material present challenging problems for numerical simulation using grid based methods. Computations invariably fail after some level of mesh distortion is reached unless suitable re-meshing is implemented to cope with the mesh distortion arising from the material deformation. The issue of mesh distortion and the subsequent re-meshing are topics of much research for grid based methods. These problems can be overcome by using a mesh-less numerical framework. In this paper, the application of a mesh-less method called Smoothed Particle Hydrodynamics (SPH) for modelling three-dimensional complex forging processes is demonstrated. It is shown that SPH is a useful simulation method for obtaining insights into the material deformation and flow pattern during forging of realistic industrial components. The effect of process parameters and material properties on the quality of the forged component is evaluated via SPH simulations. This includes the determination of forging force required for adequate die filling which is an important criterion for die designs. Material hardening, controlled by the degree of heat treatment, is found to have a profound effect on the material deformation pattern and the final product. Forging defects such as incomplete die filling, asymmetry in forged components, flashing and lap formation are shown to be predicted by SPH. SPH can thus potentially be used both for assessment of the quality of forged products and evaluation of prototype forging system designs. [Copyright &y& Elsevier]

Abstract: Recently, a floating crane is frequently used for the block lifting, transportation, turn-over, and assembly processes in waves. For these production processes, it is important to detect collision in advance between assembly blocks or the block and the other facilities like the wire rope and the barge which are carrying the block. The tension of the wire rope also needs to be calculated to check that the maximum value is less than the safety criteria. In this paper, a mathematical model is constructed based on multibody system dynamics considering the external forces such as the hydrostatic, hydrodynamic, wind force, etc. To observe the dynamic motions of the floating crane and the block, and to calculate the tension of the wire rope, the time and event simulations are performed by solving the mathematical model in the computer. For applying the simulations to the various production processes in shipyards, a simulation framework is developed. The simulation framework consists of a simulation kernel, application-specific modules, a simulation coordinator, development tools, and post-processing tools. The simulation kernel manages both DEVS (discrete event system specification) and DTSS (discrete time system specification) to deal with various simulation requests. The application-specific modules provide the functions used in application systems, such as dynamic analysis, collision detection, visualization, wire rope force calculation, hydrostatic force calculation and hydrodynamic force calculation. The simulation coordinator manages the data of the simulation kernel and the application-specific modules. The development tools provide a development process, a scenario manager, and a simulation model generator. The post-processing tools are used to report the simulation results. The examples of block lifting, transportation, turn-over, and assembly simulations are developed based on the framework to show that the framework is useful for the simulations of the production processes using one or more floating cranes. [Copyright &y& Elsevier]

Abstract: When sailing in seawater, the forces exerted to torpedo are complicated and can’t be precisely measured, especially the hydrodynamic parameters. So it is very important to establish non-linear mathematics models of torpedo moving characteristics in torpedo weapon development course. Firstly, according to torpedo underwater motion characteristics, this paper analyzes all kinds of forces and moments exerted to torpedo. Then based on momentum theorem and momentum moment theorem, torpedo spatial motion dynamic equations are established. Combining with torpedo kinematic equations and control system equations, simulation program written by standard C language are compiled and carried out successfully in Visual C++ 6.0 compilation environments. Finally several typical simulation figures and analysis are presented. Simulation results show that torpedo spatial motion mathematics models are accord with torpedo motion characteristics in real voyage course, having better usability and expansibility, and can satisfy the design need preferably. [Copyright &y& Elsevier]

Abstract: This paper is mainly dedicated to the presentation of a general method to couple standard finite elements with SPH methods for fast transient analysis. The method is based on hand shake formulation and developed for fast transient. This type of gluing permits to use SPH only in the region of interest. The SPH methods is often CPU time consuming, hence this coupling strategy is interesting provided one knows in advance where the critical zone is. The method is applied to the prediction of perforation of available reinforced concrete slabs experiments. A concrete damage model adapted to high strain rate is also described. [Copyright &y& Elsevier]

Abstract: The paper describes the use of the grid-free Smoothed Particle Hydrodynamics (SPH) method to investigate lava flow from volcanic eruptions using real three dimensional topography in the form of Digital Terrain Models (DTM). Heat transfer resulting from conduction and radiation and solidification of the lava modelled via a variable viscosity are coupled to the fluid flow solution. Simulations show that the run-out distance and the nature of the lava flow are affected significantly by the lava viscosity and that this is dependent on the scale of the volcanic eruption, with solidification effects strongest on the smallest scale. SPH appears to be a highly effective technique for predicting lava flow with very good representations of the fluid free surface, close interaction with the complex topography, easy inclusion of the thermal and solidification effects leading to very plausible flow predictions. The pile-up of the lava at the front as it solidifies and the subsequent deceleration of the flow are easily modelled by SPH. [Copyright &y& Elsevier]

Abstract: Aircraft are subjects to a number of unpredictable loadings that can seriously affect their performance. In the spirit of ever increasing the safety of passengers, hail impact has been studied. This paper shows the progress that has been made using pressure sensitive film to measure the hail impact event. Moreover, the smooth particle hydrodynamics (SPH) method in LS-DYNA is used to create a numerical model in order to validate the numerical hail model so that it can be used in future advanced simulations of hail impact on components of aircraft. Results show that the SPH method can be effectively used to create a numerical hail model and that pressure sensitive film is a simple and inexpensive tool to capture the experimental data. [Copyright &y& Elsevier]

Abstract: This paper describes the development of a numerical model for wave overtopping on seadikes. The model is based on the flux-conservative form of the nonlinear shallow water equations (NLSW) solved with a high order total variation diminishing (TVD), Roe-type scheme. The goal is to reliably predict the hydrodynamics of wave overtopping on the dike crest and along the inner slope, necessary for the breach modelling of seadikes. Besides the mean overtopping rate, the capability of simulating individual overtopping events is also required. It is shown theoretically that the effect of wave breaking through the drastic motion of surface rollers in the surfzone is not sufficiently described by the conventional nonlinear shallow water equations, neglecting wave setup from the mean water level and thus markedly reducing the model predictive capacity for wave overtopping. This is significantly improved by including an additional source term associated with the roller energy dissipation in the depth-averaged momentum equation. The developed model has been validated against four existing laboratory datasets of wave overtopping on dikes. The first two sets are to validate the roller term performance in improving the model prediction of wave overtopping of breaking waves. The last two sets are to test the model performance under more complex but realistic hydraulic and slope geometric conditions. The results confirm the merit of the supplemented roller term and also demonstrate that the model is robust and reliable for the prediction of wave overtopping on seadikes. [Copyright &y& Elsevier]

Abstract: A generic numerical model which is valid both in the strong inversion regime and sub-threshold regime for the detection of terahertz radiation utilizing Metal–Oxide–Semiconductor (MOS) Field-Effect Transistors (FETs) is developed in this paper. A general carrier density equation and gate leakage current are coupled to the basic hydrodynamic equations which govern the electron transport in the 2D channel of the MOS field-effect transistor to obtain the numerical solution; a progress-based photo-response signal of the terahertz radiation of MOSFET is calculated. The simulation results are compared with existing analytical results, proving the validity of the proposed numerical model and overcoming limitations of the analytical theories. [Copyright &y& Elsevier]

Abstract: This work aims to demonstrate an advancement towards the integrated modelling of surf zone hydrodynamics by means of a VOF-type numerical model (COBRAS-UC) based on the Reynolds-Averaged Navier–Stokes equations. In this paper, the numerical model is adapted and validated for the study of nearshore processes on a mildly-sloping beach. The model prediction of wave energy transformation and higher order statistics (skewness and asymmetry) are in good agreement with detailed laboratory observations from a barred beach [Boers, M. (1996). “Simulation of a surf zone with a barred beach; Report 1: Wave heights and wave breaking”. Tech. Rep.96-5, Comm. on Hydrol. and Geol. Eng., Dept. of Civil Engineering, Delft University of Technology]. Moreover, the numerical model allows us to study the low-frequency motions inside the surf zone. It is found that in order to achieve a satisfactory simulation of both short- and long-wave transformation, the numerical model must achieve: (i) the simultaneous second-order wave generation and absorption, (ii) the energy transfer between triad of components, (iii) the short- and long-wave energy dissipation inside the surf zone, and (iv) the wave reflection at the shoreline. Comparisons between numerical and experimental results demonstrate the model capability to satisfactorily simulate all the aforementioned processes. [Copyright &y& Elsevier]

Abstract: In this paper a nonlinear dynamic PDE formulation for a pipe string suspended from a pipelay vessel to the seabed in a pipelay operation is developed. This model extends a three-dimensional beam model capable of undergoing finite extension, shearing, twist and bending, to apply for marine applications by adding the effects of restoring forces, hydrodynamic drag and seabed interaction. The model is validated against the natural catenary equation and the FEM code RIFLEX. The model is extended to include the pipelay vessel dynamics by applying a potential theory formulation of a surface vessel, suited for dynamic positioning and low speed maneuvering, as a boundary condition for the PDE. This system is found to be input–output passive and stable. Pipeline installation applications where the presented model is suited are e.g., analysis and simulation of the installation operation, operability analysis, hardware-in-the-loop (HIL) testing for vessel control systems, and automation of the pipelay operation. [Copyright &y& Elsevier]

Abstract: In this paper, bubble–particle collision efficiency in a turbulent flow is investigated from a multiscale modelling viewpoint. An integrated CFD-based scheme for the prediction of turbulent bubble–particle collision efficiency is developed. As part of this scheme, the effect of turbulence and the bubble wall effect on bubble–particle collision efficiency are systematically studied using a 3D low turbulent Reynolds number shear-stress-transport turbulence model. Example simulations and comparisons are carried out to illustrate the methodology. The method can also be applied to non-Newtonian slurries. [Copyright &y& Elsevier]

Abstract: Understanding how a bioreactor functions is a necessary precursor for successful reactor design and operation. This paper describes a two-dimensional computational fluid dynamics simulation of three-phase gas–liquid–solid flow in an expanded granular sludge bed (EGSB) reactor used for biohydrogen production. An Eulerian–Eulerian model was formulated to simulate reaction zone hydrodynamics in an EGSB reactor with various hydraulic retention times (HRT). The three-phase system displayed a very heterogeneous flow pattern especially at long HRTs. The core-annulus structure developed may lead to back-mixing and internal circulation behavior, which in turn gives poor velocity distribution. The force balance between the solid and gas phases is a particular illustration of the importance of the interphase rules in determining the efficiency of biohydrogen production. The nature of gas bubble formation influences velocity distribution and hence sludge particle movement. The model demonstrates a qualitative relationship between hydrodynamics and biohydrogen production, implying that controlling hydraulic retention time is a critical factor in biohydrogen-production. [Copyright &y& Elsevier]

Abstract: This paper describes the development of a model of the application nip of a forward roll coater and its use to investigate the hydrodynamics of non-Newtonian industrial coating formulations. The focus of the work is on the simulation of the roll deformation and its relationship with the hydrodynamics in the nip. The free surface movement of the fluid domain is included in the model, and is coupled to the deformation of the elastomer-covered roll for the case of a negative gap. An iterative approach is used, whereby the free surface movement is adjusted according to the normal velocity component along the boundary. The governing equations are solved with the finite element method and adaptive re-meshing of the domain between iterations. The elastomer deformation is modeled using a two-dimensional approach, where the elastomer/liquid interface is updated using the force balance at the surface. The solid and fluid problems are solved in a de-coupled manner, in which each problem is solved separately and alternately until final overall convergence is obtained. A comparison with recently obtained data shows a close match between experiment and simulation. Finally, the methodology is applied to investigate the effect on the pressure profile of the properties of non-Newtonian Kaolin-latex coating formulations and roll speeds typical of those in the industry. The results show that the proposed model can help gain insight into the mechanisms that govern this type of coating process. [Copyright &y& Elsevier]

Abstract: This paper investigates the effect of natural and artificial morphological changes in a tidal inlet on the tidal propagation and on the water exchanges with the sea, through data analysis and numerical modeling. Bathymetric and tidal data reveal a strong seasonal signal, as a result of the changes in the relative importance of tidal and wave action: during the maritime winter the M2 tidal amplitude decreases by 50% and flood dominance increases. This trend is reverted during maritime summer, and tidal amplitudes can be further enhanced by dredging of the inlet. Hydrodynamic and residence time (RT) simulations were set up for three different bathymetric configurations of the lower lagoon, representative of distinct situations. Hydrodynamic results confirmed that tidal propagation depends strongly on the bathymetric configuration. At the transitions between channels, tidal energy losses occur and flood dominance increases. Dredging the channels and repositioning the inlet throat improve tidal propagation and promote sediment flushing to the sea. The spatial variability of RTs was evaluated through the integration of individual particle results in morphologically relevant units, while time variability was examined within the tidal and neap/spring cycles. Residence times depend heavily on the morphological changes associated with both dredging operations and inlet migration, and on the particle release time, both within the tidal cycle and within neap/spring cycles. The relative importance of each of these factors depends on the particle location within the lagoon. The upstream regions of the lagoon have very large RTs (years), as a result of the small tidal amplitudes and velocities. In some of these regions, RTs vary by a factor of 4 depending on the bathymetry of the inlet. In the lower lagoon, tidal amplitude also has a significant effect on RTs. Dredging the channels and repositioning the inlet throat from the southern margin to a central position improves the flushing of both southern and northern channels. [Copyright &y& Elsevier]

Abstract: We investigated planktonic larval transport processes along an axially symmetric mid-ocean ridge with characteristics similar to that of the East Pacific Rise (EPR) segment at 9–10°N. The hydrodynamic basis for this study is a primitive equation model implemented in two dimensions (depth and across-ridge), forced at the open boundaries to provide suitably realistic simulation of currents observed on the EPR ridge crest from May to November 1999. Three-dimensional trajectories of numerical larvae are computed assuming homogeneity in currents in the along-ridge direction. Larval dispersal fluctuates significantly in time. Transport distance decreases systematically with height above the bottom where numerical larvae are less subject to strong currents along the flanks of the ridge. The probability that the simulated larvae will be located near the ridge crest at settlement depends strongly on their behavioral characteristics (vertical position in the water column during the larval stage) and the length of their precompetency period. [Copyright &y& Elsevier]