Smoothed Particle Research Articles

A numerical study on a winglet floating breakwater: Enhancing wave dissipation performance

Box-type floating breakwaters (FBs), widely used for marine protection, face challenges in their wave dissipation capabilities. Although the effectiveness of the winglet-type floating breakwater in improving wave dissipation has been recognized, the specific mechanisms involved are not fully understood. This research presents an innovative winglet breakwater design, featuring three unique winglet configurations: 4-wings, Down-wings, and Up-wings. The study examines its performance against both regular and irregular waves using the Smooth Particle Hydrodynamics (SPH) method, taking into account factors such as the wave period, FB immersion depth, and FB relative density. Numerical simulations indicate a marked enhancement in wave dissipation for the FB equipped with four winglets compared to a baseline model without winglets. The Response Amplitude Operator (RAO) amplitude for the winglet-equipped FB is notably lower, approximately half that observed in the baseline scenario. Notably, the winglet FB's performance in irregular waves outperforms that in regular wave conditions. The insights gained from the design of these winglets provide significant contributions to practical engineering applications.

Numerical Analyses of Perforation and Formation Damage of Sandstone Gas Reservoirs

Shaped charge perforation is an important technology for sandstone gas reservoirs. In the process of shaped charge perforating, the initial permeability and porosity of the formation are greatly reduced, directly affecting oil and gas production. This paper uses smooth particle hydrodynamics (SPH) and finite element methods (FEMs) to study the formation damage caused by the shaped charge perforation. In this perforation simulation, the impact characteristics of the metal jet formed by the liner are coupled with the damage characteristics of the sandstone. A new mathematical model is proposed to describe the damage of permeability and porosity based on the Morris and Xue models. The simulated results show that a large-scale abdominal section appears at the perforation site, and the axis of the hole tilts with the increase in the perforation depth. The porosity damage at the perforation site is the greatest, up to 60%, while the permeability recovers to 90% of its initial state after pressure relief. The degree of porosity damage decreases with the increase in negative pressure, and when the negative pressure is 30 MPa, it may cause a large amount of sand production.

Discussion on “comparative study on volume conservation among various SPH models for flows of different levels of violence, coastal engineering, volume 191, August 2024, 104 521” by Wang et al

The paper by Wang et al. (2024) targets an interesting topic in the context of particle methods, namely, volume conservation. This important feature is studied by focusing on the time variation of mean water level under three different scenarios corresponding to hydrostatics, standing wave and dam break, and through consideration of a few variants of the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) fluid model. In this discussion, the discussers briefly discuss some issues that could have been further considered in the paper by Wang et al. (2024) to ensure rigorousness and comprehensiveness of the conducted comparative analysis.

Developing a Three-Dimensional Bubble Dynamics Model for Centrifugal Nuclear Thermal Propulsion

Nuclear thermal propulsion (NTP) is a highly efficient type of propulsion system that could yield a specific impulse up to 800 s. High-performance NTP allows for possibilities of various mission types from flyby to interplanetary flight, manned or unmanned. Centrifugal nuclear thermal propulsion (CNTP) is a type of NTP that uses liquid fissile material instead of a solid core in a standard reactor configuration. CNTP requires an interaction between liquid fissile fuel and gaseous propellant to perform heat transfer and generate thrust in a spinning enclosure. Because of the liquid state of the fissile fuel, it is essential to monitor bubble behavior and trajectory. For example, the bubble dwell time within the liquid and hydrogen flow rates can influence the liquid volume fraction and volume, which in turn can affect reactivity. A model is developed and presented that, as it matures, will predict the bubbles’ behavior based on the various types of liquid and gas and their corresponding properties as well as assist in cross-validation with the concurring experiment. The model primarily utilizes the smooth particle hydrodynamics (SPH) approach to simulate the liquid and gas interaction within the design space. The physics include buoyancy and drag on the bubbles. The pressure field within the liquid is modeled using hydrostatics, in which centrifugal motion introduces a radial gradient. Boundary conditions are devised to confine the liquid and gas within the enclosure. In this paper, we present the progress to date in two centrifugal fuel element–relevant subscale devices, the so-called “Antfarm” and “Blender II.” Antfarm is a static stage in a rectangular enclosure where buoyancy is purely gravity driven. Blender II refers to a rectangular enclosure that spins at up to 7000 rpm. Both Antfarm and Blender II are experiments that provide important data for validation against our SPH model. Two liquid and gas combinations are modeled in the present study using the Antfarm setup: water-air, and Galinstan-Nitrogen. The bubbles’ behavior was comparable to the experiment, and the velocity was at the same order of magnitude. The liquid simulation performed for the Blender II model shows that the pressure gradient within the liquid in the radial direction matches that predicted analytically from the centrifugal acceleration. The Blender II liquid model awaits experimental data for validation and verification.

Simulation of RBC Dynamics in Oscillatory Flow Using Smoothed Particle Hydrodynamics

Simulation of RBC Dynamics in Oscillatory Flow Using Smoothed Particle Hydrodynamics

Particle-based modelling of laser powder bed fusion of metals with emphasis on the melting mode transition

The laser-beam powder bed fusion process for metals, commonly abbreviated as PBF-LB/M, is a widely used process for the additive manufacturing of parts. Numerical simulations are useful to identify optimal process parameters for different materials and to obtain detailed insights into process dynamics. The present work uses a single-phase incompressible Smoothed Particle Hydrodynamics (SPH) scheme to model PBF-LB/M which was found to reduce the required computational time and significantly stabilize the partially violent flow in the melt pool in comparison to a weakly compressible SPH approach. The laser-material interaction is realistically modelled by means of a ray tracing method. An approach to model the effective thermal coductivity of the powder bed is proposed. Excellent agreement between the simulation results and experimental X-ray analyses of the transition from conduction melting mode to keyhole mode including geometric properties of the vapor depression zone was found. These results prove the usability of SPH as a high precision simulation tool for PBF-LB/M.Graphic abstract

SPH modeling and investigation of the effect of the carbon dioxide entry form on its absorption rate in a microchannel containing absorbent aqueous solution

Carbon capture technology is a rapidly growing and developing field that has seen extensive research conducted in both experimental and numerical studies. The majority of numerical simulations conducted thus far have primarily concentrated on mesh-based methods, disregarding the potential of full Lagrangian methods in accurately simulating multiphase and intricate flows. Consequently, this research aims to address this gap by introducing, for the first time, the application of the Lagrangian Smoothed Particle Hydrodynamics (SPH) method to simulate and analyze the process of carbon dioxide absorption in an aqueous solution. The first step in this study involves developing a suitable and relatively accurate algorithm based on the governing equations of carbon dioxide absorption. These equations encompass mass and momentum conservation, heat transfer, mass transfer, and chemical reactions. Once the algorithm is developed, it is validated through computational code and the optimal grid of particles is selected for calculations. Subsequently, three different scenarios for the entry of carbon dioxide into the aqueous solution are modeled and discussed. The results reveal that as the number of carbon dioxide inputs increases, the instabilities of the two-phase flow along the microchannel also increase. These instabilities significantly enhance the rate of carbon dioxide absorption. Overall, this study highlights the importance of considering Lagrangian methods, specifically the SPH method, in simulating multiphase and complex flows in carbon capture technology. The findings contribute to a better understanding of the carbon dioxide absorption process and can potentially aid in the development of more efficient carbon capture systems.

New design of materials, order and thicknesses of an aircraft windshield behaviour layers to increase its resistance against repeated bird impacts

Abstract There are instances when an aircraft encounters a bird’s flock or faces a heavy hailstorm, causing the windshield to sustain consecutive impacts. Therefore, the investigation of windshield resistance against repeated impacts is crucial. In this research, various tests such as tensile, split Hopkinson pressure bar (SHPB), and three-point bending are conducted to extract the mechanical properties of the materials used in a five-layers windshield under high strain rates. Using this information, the bird impact on the windshield is simulated using the smooth particle hydrodynamics (SPH) method, and the results are compared with real bird impact test outcomes, and the validation of this simulation is confirmed. The simulation of two consecutive bird strikes indicates the current windshield lacks sufficient resistance against successive dual impacts; in such scenarios, the second bird penetrates the windshield after breaking it and tearing the interlayer. Considering new materials and thicknesses for each windshield layer, a Taguchi experimental design method is employed to examine various layer arrangements with different materials and thicknesses. The configurations in which the windshield can withstand a maximum of three bird impacts in succession are identified. Subsequently, using the “the smaller, the better” criterion in the Taguchi optimisation approach, the configuration that not only prevents bird penetration but also minimises the maximum strain in the inner layer is selected as the desired outcome. Thus, a new five-layer windshield with new materials and thicknesses is presented, which is resistant to the repeated collision of up to three birds, tearing in the interlayer and bird penetration does not happen.

Simulation study on the damage behavior of tantalum target plates under high-velocity projectile impact

This study aims to explore the damage behavior of tantalum target plates under high-velocity projectile impact, addressing the threats of damage in the aerospace field due to debris and other factors. With the advent of low-cost space launches and large satellite projects, spacecraft such as space stations are facing increasingly severe collision risks. The research utilizes numerical simulation techniques, based on ANSYS/AUTODYN software and the Smoothed Particle Hydrodynamics (SPH) method, to simulate the impact process of projectiles of different velocities (1 ∼ 10 km/s) and materials (aluminum and steel) on tantalum target plates. The results are intended to provide theoretical support for the design of spacecraft protection structures and contribute data support for establishing a millimeter-level space debris impact database.

Structural and Optical Properties of Fe Doped Tio<sub>2</sub> Nanoparticles: Investigation of Effects of Different Doping Concentration

Fe-doped TiO<sub>2</sub> nanoparticles (F-T NPs) were synthesized using the sol-gel method where different molar concentrations (0, 1, 2, 3, 5, 7, 9, and 10%) of Iron (iii) nitrate were added to a constant amount of the metal precursor TetraisopropylOrthotitanate (TTIP) solution, the solvent precursor ethanol and refluxing agent diethanolamine at the ratios of 1:6:1 respectively. The gel formed was annealed at 500°C in a muffle furnace for 2h. Fourier Transform Infrared (FTIR) showed Fe-O symmetrical stretching vibration for the 5% doping and above and Ti-O-Fe asymmetrical stretching vibration at wavenumber 668 cm<sup>-1</sup> and 1033cm<sup>-1</sup>, respectively. Fe-O stretching vibration confirms substitution doping. The crystallite size was calculated using the Debye Scherer equation; 2% F-T NPs had the largest crystallite size at 16.45 nm, and 7% F-T NPs had the least size at 10.95 nm, a decrease of 2.80 nm from the 0% F-T NPs. X-ray diffraction spectra showed a merging of peaks at planes 105 and 211. The peak at plane 204 is found to diminish, and the growth of another peak at 2θ (64.28°). Optical analysis was studied using UV-Vis, where the Tauc plot estimated the calculated band gap (E<sub>g</sub>). It was the least at 7% F-T NPs with a value of 4.41 eV, and 5% F-T NPs were found to have the highest value of 4.86 eV.% Transmittance is directly proportional to the optical band gap. Scanning Electron Microscope showed improved agglomeration and aggregation with a dense and smooth particle. Energy Dispersive Spectroscopy confirmed the presence of Fe, Ti, and O in the F-T NPs.

Lactoferrin thermal stabilization and iron(II) fortification through ternary complex fabrication with succinylated sodium caseinate

A thermally stable co-delivery system for lactoferrin (LF) and iron(II) was developed to address iron deficiency anemia. Complexes were formed between LF, succinylated sodium caseinate (S.NaCas) and FeSO4 with high yield (∼85%). LF-S.NaCas-Fe complexes achieved loading capacities for iron(II) between 2.5 and 12 mg g–1and LF loading capacities between 250 and 690 mg g−1, depending upon initial Fe2+ concentrations and LF ratios. The LF-S.NaCas complex mixtures appeared as smooth cubic particles in SEM, and gradually aggregated to amorphous particles as th iron(II) concentration increased due to iron-facilitated cross-linking. The complexation significantly improved LF thermal stability and addressed the poor solubility of iron(II) under neutral pH. After thermal treatment (95 °C, 5 min), the rehydrated complexes retained 68%–90% LF, with <10% iron(II) release. Circular dichroism spectra showed the secondary structure of the complexed LF was well retained during thermal treatment. This thermally stable system showed great potential in LF thermal protection and iron(II) fortification.

Development of pH-responsive Eudragit S100-functionalized silk fibroin nanoparticles as a prospective drug delivery system.

Silk fibroin nanoparticles (FNP) have been increasingly investigated in biomedical fields due to their biocompatibility and biodegradability properties. To widen the FNP versatility and applications, and to control the drug release from the FNP, this study developed the Eudragit S100-functionalized FNP (ES100-FNP) as a pH-responsive drug delivery system, by two distinct methods of co-condensation and adsorption, employing the zwitterionic furosemide as a model drug. The particles were characterized by sizes and zeta potentials (DLS method), morphology (electron microscopy), drug entrapment efficiency and release profiles (UV-Vis spectroscopy), and chemical structures (FT-IR, XRD, and DSC). The ES100-FNP possessed nano-sizes of ∼200-350 nm, zeta potentials of ∼ -20 mV, silk-II structures, enhanced thermo-stability, non-cytotoxic to the erythrocytes, and drug entrapment efficiencies of 30%-60%, dependent on the formulation processes. Interestingly, the co-condensation method yielded the smooth spherical particles, whereas the adsorption method resulted in durian-shaped ones due to furosemide re-crystallization. The ES100-FNP adsorbed furosemide via physical adsorption, followed Langmuir model and pseudo-second-order kinetics. In the simulated oral condition, the particles could protect the drug in the stomach (pH 1.2), and gradually released the drug in the intestine (pH 6.8). Remarkably, in different pH conditions of 6.8, 9.5, and 12, the ES100-FNP could control the furosemide release rates depending on the formulation methods. The ES100-FNP made by the co-condensation method was mainly controlled by the swelling and corrosion process of ES100, and followed the Korsmeyer-Peppas non-Fickian transport mechanism. Whereas, the ES100-FNP made by the adsorption method showed constant release rates, followed the zero-order kinetics, due to the gradual furosemide dissolution in the media. Conclusively, the ES100-FNP demonstrated high versatility as a pH-responsive drug delivery system for biomedical applications.

Study on Water Entry of a 3D Torpedo Based on the Improved Smoothed Particle Hydrodynamics Method

The water entry of a torpedo is a complex nonlinear problem, involving transient impact, free surface deformation, droplet splashing, and fluid–structure coupling, which poses severe challenges to traditional mesh methods. The meshless smoothed particle hydrodynamics (SPH) method shows unique advantages in capturing the complex features of the water entry of the torpedo at different entry angles. However, it still suffers from some inherent shortcomings, such as low surface discretization accuracy, poor discretization flexibility, and low calculation efficiency. In this study, an improved adaptive SPH algorithm is proposed to investigate the water entry of the torpedo accurately and efficiently. This method integrates meshless point generation and adaptive techniques simultaneously. The numerical results demonstrate that when the torpedo vertically enters the water at different velocities, the induced impact loads acting on the head of the torpedo fluctuate significantly with two peak values in the initial stage and thereafter stabilize in a later stage. The impact load acting on the torpedo, the entry depth of the torpedo, the splash height of the droplets, and the size of the cavity generated around the torpedo increase with the increment in the entry velocity. When the torpedo enters the water at different entry angles under the same initial entry velocity, both the vertical and the horizontal movements of the torpedo are observed, which results in more complex variations in parameters along the x- and y-axes. The findings and the corresponding numerical method in this study can provide a certain basis for the future designs of the entry trajectory and the structural bearing capacity of torpedoes.

Analysis of fluid force and flow fields during gliding in swimming using smoothed particle hydrodynamics method

Gliding is a crucial phase in swimming, yet the understanding of fluid force and flow fields during gliding remains incomplete. This study analyzes gliding through Computational Fluid Dynamics simulations. Specifically, a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method for flow-object interactions is established. Fluid motion is governed by continuity, Navier-Stokes, state, and displacement equations. Modified dynamic boundary particles are used to implement solid boundaries, and steady and uniform flows are generated with inflow and outflow conditions. The reliability of the SPH model is validated by replicating a documented laboratory experiment on a circular cylinder advancing steadily beneath a free surface. Reasonable agreement is observed between the numerical and experimental drag force and lift force. After the validation, the SPH model is employed to analyze the passive drag, vertical force, and pitching moment acting on a streamlined gliding 2D swimmer model as well as the surrounding velocity and vorticity fields, spanning gliding velocities from 1 m/s to 2.5 m/s, submergence depths from 0.2 m to 1 m, and attack angles from −10° to 10°. The results indicate that with the increasing gliding velocity, passive drag and pitching moment increase whereas vertical force decreases. The wake flow and free surface demonstrate signs of instability. Conversely, as the submergence depth increases, there is a decrease in passive drag and pitching moment, accompanied by an increase in vertical force. The undulation of the free surface and its interference in flow fields diminish. With the increase in the attack angle, passive drag and vertical force decrease whereas pitching moment increases, along with the alteration in wake direction and the increasing complexity of the free surface. These outcomes offer valuable insights into gliding dynamics, furnishing swimmers with a scientific basis for selecting appropriate submergence depth and attack angle.

Dynamic analysis of field-scale rockslides based on three-dimensional discontinuous smoothed particle hydrodynamics: A case study of Tangjiashan rockslide

To improve the understanding of the dynamic disastrous process of field-scale rockslides, a novel numerical approach, Three-dimensional Discontinuous Smoothed Particle Hydrodynamics (3DSPH), was originally developed. This method comprehensively captures sequential stages of crack initiation and propagation, formation of contacts, frictional slip, catastrophic slides of rock masses, and final deposition, which was verified by three benchmark tests including the bouncing test of rigid balls, block sliding test and unconfined compression test of layered rock specimens. The approach was subsequently employed in the case of the Tangjiashan rockslide blocking valley event with particular attention paid to the influence of layered rock structure on the sliding and deposition processes. Field survey, geomorphological analysis and laboratory test of rock specimens were conducted to determine fundamental geological conditions and parameters required by the numerical simulation. Finally, 3D rockslide simulations with different rock layer thickness and strength subject to seismicity were conducted. The duration of the actual Tangjiashan rockslide's valley-blocking event (approximately 60 s) and the deposition area derived from the numerical simulation closely align with the field investigation. The rockslide mode is characterized by an ‘en masse’ motion with a peak sliding velocity of approximately 35–37 m/s. This single numerical code systematically elucidated the authentic attributes of the sliding process of large-scale rockslides, and realistically captured the characteristics of preservation of layered features within the sliding mass and ‘high-speed and short-distance’ movements with fluidization. These insights offer a fresh perspective for understanding the dynamics of large-scale rockslides with complex geological structures and subsequent accumulation processes.

Metal-silicate mixing in planetesimal collisions

Impacts between differentiated planetesimals are ubiquitous in protoplanetary discs and may mix materials from the core, mantle, and crust of planetesimals, thus forming stony-iron meteorites. The surface composition of the asteroid (16) Psyche represents a mixture of metal and non-metal components. However, the velocities, angles, and outcome regimes of impacts that mixed metal and silicate from different layers of planetesimals are debated. Our aim is to investigate the impacts between planetesimals that can mix large amounts of metal and silicate, and the mechanism of stony-iron meteorite formation. We used smooth particle hydrodynamics to simulate the impacts between differentiated planetesimals with various initial conditions that span different outcome regimes. In our simulations, the material strength was included and the effects of the states of planetesimal cores were studied. Using a statistical approach, we quantitatively analysed the distributions of metal and silicate after impacts. Our simulations modelled the mass, depth, and sources of the metal-silicate mixture in different impact conditions. Our results suggest that the molten cores in planetesimals could facilitate mixing of metal and silicate. Large amounts of the metal-silicate mixture could be produced by low-energy accretional impacts and high-energy erosive impacts in the largest impact remnant, and by hit-and-run and erosive impacts in the second-largest impact remnant. After impact, most of the metal-silicate mixture was buried at depth, consistent with the low cooling rates of stony-iron meteorites. Our results indicate that mesosiderites potentially formed in an erosive impact, while pallasites potentially formed in an accretional or hit-and-run impact. The mixing of metal and non-metal components on Psyche may also be the result of impacts.

Improved Smoothed Particle Hydrodynamics for the Three-Dimensional Solid Impact Problems

Total Lagrangian-Smoothed Particle Hydrodynamics (TL-SPH) method is an important method to improve the tensile instability of traditional SPH, but it still faces some defects, such as insufficient accuracy at boundary region, difficulty in obtaining damage and applying interface conditions. Therefore, the high-order TL-SPH is applied for the elastic–plastic solid. A damage model is proposed by adaptively transforming the type of kernel function. Furthermore, a Riemann contact algorithm is introduced for different solids. The advantages of the methods in improving tensile instability and simulating damage are verified by the cases of the plates and the notched beams with an impact load.

Effect of Geopolymerization Reaction on the Flexural Strength of Kaolin-Based Systems.

Geopolymers exhibit broad application prospects, including construction and radiation shielding, which require excellent mechanical performances. However, investigations on the nature of geopolymerization reactions and their consequential impact on mechanical performance are still vague. In this study, the effect of the major factors of Si/Al ratio and curing time on the geopolymerization reaction and flexural strength were studied based on the microstructure evolution and chemical bonding formation analyzed using the SEM, FTIR, peak deconvolution, and XRD methods. The microstructure of geopolymers was transferred from initially layered smooth particles of kaolinite to a 3D network porous structure, corresponding to sodalite. A spectrum exclusive to the geopolymer structure occurred at 973 cm-1, corresponding to the sodium aluminum silicate hydrate (N-A-S-H) links, the integral area of which represents the degree of geopolymerization reaction. Furthermore, a controllable reaction degree was achieved by adjusting the Si/Al ratio and curing time, where the maximum reaction degree of 55% was achieved at a Si/Al ratio of 1.94 when cured for 7 d. The correlation between the flexural strength and reaction degree was found to follow a proportional relationship, achieving a flexural strength of 21.11 MPa with a degree of 45%. This study provides insight into the development of mechanical strength through controlling the reaction process.

Improvement in the Accuracy and Efficiency of Smoothed Particle Hydrodynamics: Point Generation and Adaptive Particle Refinement/Coarsening Algorithms

Improvement in the Accuracy and Efficiency of Smoothed Particle Hydrodynamics: Point Generation and Adaptive Particle Refinement/Coarsening Algorithms

An improved algorithm for Finite Particle Method considering Lagrange-type remainder

The Finite Particle Method (FPM) is a significant improvement to the traditional Smoothed Particle Hydrodynamics method (SPH), which can greatly improve the computational accuracy of the entire computational domain. However, unstable calculation results and long computational time are still major obstacles to the development of FPM. Based on matrix decomposition, the fundamental equations of the traditional Finite Particle Method are rewritten and a Generalized Finite Particle Method (GFPM) is derived by introducing Lagrange-type remainder. By deriving and rewriting the fundamental equations, the GFPM method can be theoretically proven to be always stable. Numerical examples show that the GFPM method can utilize a smaller computational scale to achieve the same computational accuracy as the FPM method, with a corresponding reduction in computational time. Finally, the GFPM method is applied to a one-dimensional stress wave propagation problem and a one-dimensional heat conduction problem, and the computational results are compared with those of the SPH method and the FPM method, which verify that the GFPM has higher computational accuracy and stability.