Numerical Smoothed Particle Hydrodynamics Research Articles

Wave run-up characteristic on armour layer breakwater using the smoothed particle hydrodynamics (SPH) method

Coastal structures, such as breakwater, play a critical role in protecting shorelines from the erosive forces of waves and currents. Understanding the wave run-up phenomenon on these structures is essential for designing effective coastal defense systems. This research aims to investigate the wave run-up characteristics on an armour layer breakwater using the Smoothed Particle Hydrodynamics (SPH) method (Meshless particle method based on the Lagrangian formulation), a numerical method that captures complex fluid-structure interactions. The SPH method’s inherent ability to handle free-surface flows and dynamic interactions makes it particularly suited for simulating wave run-up. The research employs numerical testing and modelling of a non-overtopping breakwater using the smoothed particle hydrodynamics method simulated with the DualSPHysics program. The wave characteristic data used in this research are the waves on the south coast of Java. The results of this research indicate that the correlation between wave run-up characteristics (Ru/H) and the Iribarren number, both using the numerical SPH method and theory, tends to exhibit a similar pattern. Remarkably, the results from both approaches exhibit a striking similarity, revealing that as the Iribarren number increases, the incremental growth of Ru/H diminishes, eventually stabilizing at a critical threshold. The Coefficient of Determination (R2) between wave run-up characteristics (Ru/H) obtained from numerical simulations using the SPH method and Günbak’s theory is 0.8824.

Numerical Modeling of Wave Reflection from Sloped Impermeable Seawalls Using the SPH Method: Case Study of Chabahar Port

In this research, a comprehensive study is performed to investigate the interaction of regular waves with the impermeable seawall of the Chabahar port. First, a MIKE 21 SW model is used to transform the deep-water wave data to the nearshore zone. Then, the interaction of waves with the seawall is simulated using a well-known numerical smoothed particle hydrodynamics model named DualSPHysics. After validating the numerical results with the experimental data, a parametric study is performed to evaluate the effects of the wave height, wave period, and the slope of the seawall on the water level fluctuations and the wave reflection coefficient. The results showed that increasing the wave height slightly decreases the reflection coefficient. Meanwhile, a direct relationship was found between the wave height and the water level fluctuations near the wall. Generally, increasing the wave period resulted in higher reflection coefficients and water level fluctuations. Both the reflection coefficient and the water level fluctuations are greatly dependent on the slope of the seawall. Steeper slopes resulted in higher reflection coefficients and lower water level fluctuations near the seawall.

Smoothed Particle Hydrodynamics Modeling of Natural Convection Around a Heated Horizontal Cylinder: A Comparison With Experiments

AbstractAn experimental and numerical smoothed particle hydrodynamics (SPH) analysis was performed for the convective flow arising from a horizontal, thin cylindrical heat source enclosed in a glycerin-filled, slender enclosure at low Rayleigh numbers (1.18≤Ra≤242). Both the experiments and the SPH calculations were performed for positive (0.1≤ΔT≤10 K) and negative (−10≤ΔT≤−0.1 K) temperature differences between the source and the surrounding fluid. In all cases, a pair of steady, counter-rotating vortices is formed, accompanied by a plume of vertically ascending flow just above the source for ΔT>0 and a vertically descending flow just below the source for ΔT<0. The maximum flow velocities always occur within the ascending/descending plumes. The SPH predictions are found to match the experimental observations acceptably well with root-mean-square errors (RMSE) in the velocity profiles of the order of ∼10−5 m s−1. The fact that the SPH method is able to reveal the detailed features of the flow phenomenon demonstrates the correctness of the approach.

Proposal of a novel analytical wake model and array optimization of oscillating wave surge converter using differential evolution algorithm

Oscillating wave surge converters (OWSCs) have been extensively used to exploit wave energy. To maximize the energy output from an OWSC array, layout optimizations must be conducted; therefore, an analytical wake model of OWSC is needed for fast optimization iterations. However, no wake model of OWSC and no wake-model-based array optimization approach have been developed. To this end, this study proposed a novel analytical wake model of OWSC. Based on the proposed wake model and differential evolution algorithm, layout optimizations of OWSCs in wave energy farms were performed. To establish a database for deriving the analytical wake model, OWSCs were numerically simulated using the smoothed particle hydrodynamics (SPH) method, where the incoming wave height, damping of the power take-off system, and flap width were varied. The attained analytical wake model could predict the wave height changes in wake regions of OWSCs with an accuracy of 90.0% compared with the numerical SPH results. The optimized OWSC layouts demonstrated that staggered layouts with narrow and wide OWSCs placed in the front and back of wave energy farms, respectively, were economical and appropriate. Furthermore, a simplified guideline was proposed to determine OWSC layouts. Finally, all the codes implemented in this study were open-sourced.

Generating stable solitary waves with a piston-type wavemaker

The generation of stable and pure solitary waves in large-scale experimental flumes and numerical models is the focus of this study. Such waves give a better description of the target wave amplitude, has minimal amplitude dissipation during propagation and has negligible trailing waves. In the present study, the two solitary wave generation methodologies, namely, Goring's Method (GM) and the Malek-Mohammadi and Testik Method (MMTM), described in Goring (1979) and Malek-Mohammadi and Testik (2010) respectively, have been used to examine the solitary wave solutions of Boussinesq, Rayleigh, Grimshaw and Fenton, both experimentally and numerically for three different relative wave height (ε), ratios of 0.1, 0.3 and 0.6. Numerical modeling is done within a Smoothed Particle Hydrodynamics (SPH) framework developed in Valizadeh and Rudman (2017). For each ε value, we have compared the experimental and numerical results in terms of the free surface profiles and the phase speeds to give recommendations for the solitary wave solution and the generation methodology that demonstrates the best performance. Our results indicate that the Rayleigh solitary wave solution gives more accurate profiles in both experiments and numerical simulations. With respect to wave generation methodology, the MMTM gives the best results in the experiments, whereas, the GM describes the target waves better in our numerical SPH simulations.

Numerical prediction of air-assisted primary atomization using Smoothed Particle Hydrodynamics

The well defined atomization of liquid fuels plays a key role in the combustion process of civil jet engines, in particular for minimizing toxic emissions. Presently, the breakup mechanisms leading to a wide range of droplet sizes and trajectories are not understood in detail. Furthermore, reliable numerical predictions have not been feasible due to the enormous computational costs associated with the simulation of air-assisted atomization. In this paper we present a Direct Numerical Simulation (DNS) of an experimentally investigated planar prefilming air-blast atomizer at one operating point. The numerical investigation is carried out using the Smoothed Particle Hydrodynamics (SPH) method. The spatial resolution of 5 µm yields a domain size of 1.2 billion particles. Due to the superior serial and parallel performance of the method, 122 channel flow-through times of the air flow could be realized consuming a rather small amount of computational resources. Within the simulated physical period of time of 14.6 ms, two main breakup events could be detected. As a converged statistical analysis of the resulting fuel spray properties is not possible, the quantitative comparison to the experimental findings is based on single event statistics. In this work we analyze the characteristic volumetric droplet diameters DV0.1,DV0.5 and DV0.9 and the Sauter Mean Diameter D32. Both quantitatively as well as with regard to the phenomenology of the breakup processes, the simulation matches extremely well the experimental observations. This work demonstrates, that reliable simulations of air-assisted atomization have come into reach by combining the highly efficient numerical method SPH with massive computing power.

Adaptive resolution for multiphase smoothed particle hydrodynamics

The smoothed particle hydrodynamics (SPH) method has been increasingly used to study fluid problems in recent years; but its computational cost can be high if high resolution is required. In this study, an adaptive resolution method based on SPH is developed for multiphase flow simulation. The numerical SPH particles are refined or coarsened as needed, depending on the distance to the interface. In developing the criteria, reference particle spacing is defined for each particle, and it changes dynamically with the location of the interface. A variable smoothing length is used together with adaptive resolution. An improved algorithm for calculating the variable smoothing length is further developed to reduce numerical errors. The proposed adaptive resolution method is validated by five examples involving liquid drops impact on dry or wet surfaces, water entry of a cylinder and dam break flow, with the consideration of ambient gas. Different resolution levels are used in the simulations. Numerical validations have proven that the present adaptive resolution method can accurately capture the dynamics of liquid–gas interface with low computational costs. The present adaptive resolution method can be incorporated into other particle-based methods for efficient fluid dynamics simulation.

Numerical SPH analysis of debris flow run-out and related river damming scenarios for a local case study in SW China

A smoothed particle hydrodynamics (SPH) numerical modeling method implemented for the forward simulation of propagation and deposition of flow-type landslides was combined with different empirical geomorphological index approaches for the assessment of the formation of landslide dams and their possible evolution for a local case study in southwestern China. The SPH model was calibrated with a previously occurred landslide that formed a stable dam impounding the main river, and it enabled the simulation of final landslide volumes, and the spatial distribution of the resulting landslide deposits. At four different sites on the endangered slope, landslides of three different volumes were simulated, respectively. All landslides deposited in the main river, bearing the potential for either stable impoundment of the river and upstream flooding scenarios, or sudden breach of incompletely formed or unstable landslide dams and possible outburst floods downstream. With the empirical indices, none of the cases could be identified as stable formed landslide dam when considering thresholds reported in the literature, showing up the limitations of these indices for particular case studies of small or intermediate landslide volumes and the necessity to adapt thresholds accordingly for particular regions or sites. Using the occurred benchmark landslide as a reference, two cases could be identified where a complete blockage occurs that is more stable than the reference case. The other cases where a complete blockage was simulated can be considered as potential dam-breach scenarios.

Scaling laws for implicit viscosities in smoothed particle hydrodynamics

Smoothed particle hydrodynamics (SPH) is a particle-based method which solves continuum equations such as the Navier-Stokes equations. A periodic fluidic system under homogeneous shear is studied using SPH in the present work. The total pressure of the system and the shear stress contributions from the SPH interaction terms for pressure and viscosity as well as the contribution caused by velocity fluctuations are analyzed. It is found that the pressure and the shear stress contributions obey certain scaling laws depending on physical properties of the system such as compressibility, viscosity and shear rate as well as the spatial resolution. Some of the identified relations resemble scaling laws for the rheology of dense granular flows. These findings render an assessment of the convergence with respect to the spatial resolution of SPH simulations possible. Furthermore, the similarities between numerical SPH particles and physical grains in dense flow provide a deeper understanding of the nature of the SPH method.

Modelling multi-phase liquid-sediment scour and resuspension induced by rapid flows using Smoothed Particle Hydrodynamics (SPH) accelerated with a Graphics Processing Unit (GPU)

A two-phase numerical model using Smoothed Particle Hydrodynamics (SPH) is applied to two-phase liquid-sediments flows. The absence of a mesh in SPH is ideal for interfacial and highly non-linear flows with changing fragmentation of the interface, mixing and resuspension. The rheology of sediment induced under rapid flows undergoes several states which are only partially described by previous research in SPH. This paper attempts to bridge the gap between the geotechnics, non-Newtonian and Newtonian flows by proposing a model that combines the yielding, shear and suspension layer which are needed to predict accurately the global erosion phenomena, from a hydrodynamics prospective. The numerical SPH scheme is based on the explicit treatment of both phases using Newtonian and the non-Newtonian Bingham-type Herschel-Bulkley-Papanastasiou constitutive model. This is supplemented by the Drucker-Prager yield criterion to predict the onset of yielding of the sediment surface and a concentration suspension model. The multi-phase model has been compared with experimental and 2-D reference numerical models for scour following a dry-bed dam break yielding satisfactory results and improvements over well-known SPH multi-phase models. With 3-D simulations requiring a large number of particles, the code is accelerated with a graphics processing unit (GPU) in the open-source DualSPHysics code. The implementation and optimisation of the code achieved a speed up of x58 over an optimised single thread serial code. A 3-D dam break over a non-cohesive erodible bed simulation with over 4 million particles yields close agreement with experimental scour and water surface profiles.

Study of Multi-phase Flow in Porous Media: Comparison of SPH Simulations with Micro-model Experiments

Abstract We present simulations and experiments of drainage processes in a micro-model. A direct numerical simulation is introduced which is capable of describing wetting phenomena on the pore scale. A numerical smoothed particle hydrodynamics model was developed and used to simulate the two-phase flow of immiscible fluids. The experiments were performed in a micro-model which allows the visualization of interface propagation in detail. We compare the experiments and simulations of a quasistatic drainage process and pure dynamic drainage processes. For both, simulation and experiment, the interfacial area and the pressure at the inflow and outflow are tracked. The capillary pressure during the dynamic drainage process was determined by image analysis.

A new approach to model weakly nonhydrostatic shallow water flows in open channels with smoothed particle hydrodynamics

Summary A new approach to model weakly nonhydrostatic shallow water flows in open channels is proposed by using a Lagrangian meshless method, smoothed particle hydrodynamics (SPH). The Lagrangian form of the Boussinesq equations is solved through SPH to merge the local and convective derivatives as the material derivative. In the numerical SPH procedure, the present study uses a predictor–corrector method, in which the pure space derivative terms (the hydrostatic and source terms) are explicitly solved and the mixed space and time derivatives term (the material term of B1 and B2) is computed with an implicit scheme. It is thus a convenient tool in the processes of the space discretization compared to other Eulerian approaches. Four typical benchmark problems in weakly nonhydrostatic shallow water flows, including solitary wave propagation, nonlinear interaction of two solitary waves, dambreak flow propagation, and undular bore development, are selected to employ model validation under the closed and open boundary conditions. Numerical results are compared with the analytical solutions or published laboratory and numerical results. It is found that the proposed approach is capable of resolving weakly nonhydrostatic shallow water flows. Thus, the proposed SPH approach can supplement the lack of the SPH–Boussinesq researches in the literatures, and provide an alternative to model weakly nonhydrostatic shallow water flows in open channels.

Multi-phase shock simulations with smoothed particle hydrodynamics (SPH)

In this paper we present an approach to the implementation of a multi-phase description in the numerical Smoothed Particle Hydrodynamics method. The work is based on previous work, but has been modified to suit the applications of interest, in this case shock propagation through dusty gases. Theoretical models for multi-phase systems rely on the introduction of a number of terms describing the interaction between the different phases; drag and heat exchange are two examples. These terms contain parameters, the value of many of which must be determined empirically. We present results on the effect of changing values of some of the important parameters and compare our results to experimental and numerical results published in the literature. Our numerical results generally agree well with published results, taking uncertainties concerning accuracy in existing experimental data and details in the choice of parameters for numerical results into consideration. In particular, we find that a reduction in dust particle size is an efficient way of increasing shock retardation for a given dust loading.

Numerical Simulation of the Protection System of Explosive Reaction Armor

There are some extreme conditions in the process of metallic jet penetrating the explosive reaction armor (ERA), such as high instantaneity, large deformation, et al. Based on the smoothed particle hydrodynamics (SPH) method, the generalized density approximate formula is proposed and the Held criterion is introduced. Then the numerical SPH model of metallic jet penetrating the explosive reaction armor is built to study its protection mechanics. The calculation result meets well with the theoretical value. The influences of some parameters, such as thickness of plate and attacking angle, on the protecting effect of explosive reaction armor are analyzed, aiming at providing references for the related engineering application.

Are Simulations of Cold Dark Matter Consistent with Galactic-Scale Observations at High Redshift?

We compare new observations on the kinematic characteristics of the damped Lyα systems against results from numerical smoothed particle hydrodynamics (SPH) simulations to test the predictions of hierarchical galaxy formation. This exercise is particularly motivated by recent numerical results on the cross section of damped Lyα systems. Our analysis focuses on the velocity widths Δv of ≈50 low-ion absorption profiles from our sample of z > 1.5 damped Lyα systems. The results indicate that current numerical simulations fail to match the damped Lyα observations at high confidence levels (>99.9%). Although we do not believe that our results present an insurmountable challenge to the paradigm of hierarchical cosmology, the damped Lyα observations suggest that current numerical SPH simulations overlook an integral aspect of galaxy formation.

Tidal Disruption of Periodic Comet Shoemaker-Levy 9 and a Constraint on Its Mean Density

The apparent tidal disruption of Periodic Comet Shoemaker-Levy 9 (1993e) during a close encounter within ∼1.62 planetary radii of Jupiter can be used along with theoretical models of tidal disruption to place an upper bound on the density of the predisruption body. Depending on the theoretical model used, these upper bounds range from ρ c < 0.702 ± 0.080 g cm -3 for a simple analytical model calibrated by numerical smoothed particle hydrodynamics (SPH) simulations to ρ c < 1.50 ± 0.17 g cm -3 for a detailed semianalytical model. The quoted uncertainties stem from an assumed uncertainty in the perijove radius. However, the uncertainty introduced by the different theoretical models is the major source of error; this uncertainty could be eliminated by future SPH simulations specialized to cometary disruptions, including the effects of initially prolate, spinning comets. If the SPH-based upper bound turns out to be most appropriate, it would be consistent with the predisruption body being a comet with a relatively low density and porous structure, as has been asserted previously based on observations of cometary outgassing. Regardless of which upper bound is preferable, the models all agree that the predisruption body could not have been a relatively high-density body, such as an asteroid with ρ ≈ 2 g cm -3.