Hydrodynamics Method Research Articles

Ultrasonic cavitation finishing of 316 L stainless steel using different abrasive particles: A combined SPH simulation and experimental study

Ultrasonic cavitation and its driving effect on abrasive particles have been studied and applied to the surface finishing of 316 L stainless steel. To explore the influence of abrasive characteristic parameters on the surface finishing process, a cavitation-driven single abrasive impact model was established by coupling the smoothed particle hydrodynamics (SPH) method with the finite element method (FEM). The changes in the workpiece surface and the wear of abrasive particles after the impact were analysed, the effects of the abrasive particle size, material and shape were discussed, and the effectiveness of the model was verified through ultrasonic finishing experiments. SiC abrasive particles possessing irregular shape and Al2O3 abrasive particles possessing irregular and spherical shapes were used for comparison. Both simulation and experimental results indicate that the abrasive particle with a high hardness and a spherical shape has better material removal capability. However, the spherical abrasive particles tended to occur large cracks and split into small pieces, which accelerated the wear of the abrasives. In this work, the best finishing result was obtained by using irregularly shaped SiC abrasive particles, and the surface roughness Ra was improved by 12.87 %. This study provides a comprehensive understanding of the material removal process using cavitation-driven abrasives and examines the influence of key characteristics of abrasive particles. These insights are significant for advancing the application and enhancement of this technology in metal surface treatment.

A High-Order Shifted Interface Method for Lagrangian Shock Hydrodynamics

We present a new method for two-material Lagrangian hydrodynamics, which combines the Shifted Interface Method (SIM) with a high-order Finite Element Method. Our approach relies on an exact (or sharp) material interface representation, that is, it uses the precise location of the material interface. The interface is represented by the zero level-set of a continuous high-order finite element function that moves with the material velocity. This strategy allows to evolve curved material interfaces inside curved elements. By reformulating the original interface problem over a surrogate (approximate) interface, located in proximity of the true interface, the SIM avoids cut cells and the associated problematic issues regarding implementation, numerical stability, and matrix conditioning. Accuracy is maintained by modifying the original interface conditions using Taylor expansions. We demonstrate the performance of the proposed algorithms on established numerical benchmarks in one, two and three dimensions.

A simulation platform for slender, semiflexible, and inextensible fibers with Brownian hydrodynamics and steric repulsion

The last few years have witnessed an explosion of new numerical methods for filament hydrodynamics. Aside from their ubiquity in biology, physics, and engineering, filaments present unique challenges from an applied-mathematical point of view. Their slenderness, inextensibility, semiflexibility, and meso-scale nature all require numerical methods that can handle multiple lengthscales in the presence of constraints. Accounting for Brownian motion while keeping the dynamics in detailed balance and on the constraint is difficult, as is including a background solvent, which couples the dynamics of multiple filaments together in a suspension. In this paper, we present a simulation platform for deterministic and Brownian inextensible filament dynamics, which includes nonlocal fluid dynamics and steric repulsion. For nonlocal hydrodynamics, we define the mobility on a single filament using line integrals of Rotne–Prager–Yamakawa regularized singularities and numerically preserve the symmetric positive definite property by using a thicker regularization width for the nonlocal integrals than for the self-term. For steric repulsion, we introduce a soft local repulsive potential defined as a double integral over two filaments, then present a scheme to identify and evaluate the nonzero components of the integrand. Using a temporal integrator developed in previous work, we demonstrate that Langevin dynamics sample from the equilibrium distribution of free filament shapes and that the modeling error in using the thicker regularization is small. We conclude with two examples, sedimenting filaments and cross-linked fiber networks, in which nonlocal hydrodynamics does and does not generate long-range flow fields, respectively. In the latter case, we show that the effect of hydrodynamics can be accounted for through steric repulsion.

Attitude motion and nonlinear free-surface deformation of stone-skipping over shallow water

Stone-skipping is a common yet complex motion that involves rigid-body dynamics and fluid–structure interaction (FSI). While many computational fluid dynamics methods are used to simulate the interaction between a stone and fluid, little research has been done to consider the stone, fluid, and fluid boundary as a whole in a simulation. This study, focuses on the attitude motion and free-surface deformation of stone-skipping over shallow water to investigate how the boundary effect of FSI impacts ricochet behaviors. Initially, we establish an iteration framework for the stone-skipping FSI issue based on a weakly compressible smoothed particle hydrodynamics (SPH) method with a Riemann solver. We conduct particle-independence verification and simulate several cases under varying water heights. Additionally, we analyze and compare ricochets in deep and shallow cases with different incident angles and initial pitch angles. The numerical results demonstrate that in shallow flow scenarios, the “comma-shaped” high-pressure area is compressed by the stone and the fluid boundary, leading to a more moderate variation in pitch angle. Stone-skipping in shallow water typically covers a shorter distance and reaches a lower height compared to deep water cases. Changes in the incident angle show that shallow water hinders successful skipping. Futhermore, different initial pitch angles reveal that water height directly impact the stone's trajectory in both horizontal and vertical directions. These highlight the connection between motion patterns and parameters, offering a reliable numerical prediction for the stone-skipping problem using the Riemann SPH method.

Generalized and high-efficiency arbitrary-positioned buffer for smoothed particle hydrodynamics

This paper develops a generalized, high-efficiency buffer for particle generation and deletion at arbitrary-positioned in-/outlets in the smoothed particle hydrodynamics method. To achieve generality, we standardize the position comparison of particles with an arbitrary-positioned in-/outlet bound by introducing coordinate transformation. To enhance efficiency, particle candidates subjected to position comparison at a specific in-/outlet are restricted to those within the local cell-linked lists near the defined buffer region, thereby avoiding the inefficiency in the straightforward approach of sequentially checking all fluid particle positions across the computational domain. We validate the effectiveness and versatility of the developed buffer through two-dimensional and three-dimensional non-orthogonal and orthogonal, uni- and bidirectional flows with arbitrary-positioned in- and outlets, driven by pressure or velocity boundary conditions.

SPH simulations of non-isothermal viscoplastic free-surface flows incorporating Herschel-Bulkley-Papanastasiou model

In this paper, an improved smoothed particle hydrodynamics (SPH) method is employed to accurately simulate non-isothermal viscoplastic free surface flows, wherein the viscoplastic behavior of the fluid is precisely captured through the incorporation of the Herschel-Bulkley-Papanastasiou constitutive model. To suppress the non-physical oscillation arising from the weakly compressible hypothesis within the pressure field, the density dissipation term is incorporated into the mass conservation equation. To address the tensile instability arising from the uneven distribution of particles, the particle shifting technique is incorporated as a solution. To enhance the precision and ensure numerical stability of the gradient operator, a kernel gradient correction algorithm is implemented. The improved SPH method is employed for numerically simulating the non-isothermal viscoplastic mixed convection, dam-break flow and droplet impacting the solid wall. The effectiveness of the improved SPH method in tackling the complexities of non-isothermal viscoplastic fluid is validated through a rigorous comparison of its outcomes with those derived from alternative numerical methodologies. The assessment of the numerical convergence of the improved SPH method is undertaken through the utilization of varying initial particle spacings. The numerical outcomes demonstrate that the improved SPH method adeptly and precisely delineates the heat transfer mechanisms, intricate rheological properties, as well as the dynamic variation characteristics of the free surface in non-isothermal viscoplastic free surface flows.

Numerical investigation of free surface flow impact using an accelerated three-dimensional smoothed particle hydrodynamics

Water impact problems are inevitable in the realm of ocean engineering. The smoothed particle hydrodynamics method (SPH), as a meshless particle approach, can effectively reproduce the slamming process which involves large deformation of the free surface. In this study, an accelerated three-dimensional SPH model is constructed based on the graphic processing unit (GPU) with the speedup of up to 40. The six-degree-of-freedom motion equation is introduced to realize the responses of the solid. The fluid-solid interaction system is achieved by regarding the rigid body as the moving boundary of the fluid. The computational accuracy and efficiency of the developed model are respectively verified by the wedge water entry, dam breaking and inclined cylinder water entry. Finally, the developed model is applied to a complex flight vehicle landing problem, and the effect of the initial horizontal velocity, vertical velocity and pitch angle on the impact process are qualitatively and quantitively studied.

Analysis and Application of Particle Backtracking Algorithm in Wind–Sand Two-Phase Flow Using SPH Method

Due to the high sensitivity of grid-based micro-scale wind–sand flow models to deformation and distortion, this study employs the Smooth Particle Hydrodynamics (SPH) method for numerical simulations. The advantage of the SPH method is that it can dynamically analyze the entire trajectory of the particles, thus allowing the initial positional distribution of sand-buried particles to be traced. This study utilizes the advantages of the SPH method. It develops particle backtracking algorithms based on the SPH method using the C language. It analyses the initial location distribution, concentration, velocity, and particle size distribution of sand-buried particles to formulate targeted measures to cope with wind–sand disasters. Meanwhile, this paper improves a particle modeling algorithm to realize arbitrary mixing particle size and mixing ratio by programming in C language and combining it with pixel recognition technology. In addition, this paper will use the particle backtracking algorithm to analyze the classical embankment wind and sand flow field and then propose adequate measures for embankment wind and sand disaster management by investigating sand particle movement characteristics.

3D WCSPH modelling of landslide-water dynamics during 1963 Vajont disaster

This study illustrates the full-scale 3D numerical simulation of the coupled water-landslide dynamics of the 1963 Vajont catastrophic event. The focus is given to the early phase of the event when about 270 million cubic meters of rock fell into the reservoir within an estimated runout time of about 25 s. A complex surge wave system developed throughout the basin in the first 40–55 s, producing maximum run-up of 270 m above the dam crowning. The mesh-free Lagrangian Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) method is adopted to discretize and solve the coupled system of governing equations for the landslide and water dynamics. The adopted model, which is based on SPHERA v.9.0.0 (Amicarelli et al. Comput Phys Commun, 2020), has been derived by introducing relevant modifications in the research code SPHERA (RSE SpA). The derived model is validated and the influence of water saturated soil on prediction of surge wave run-up is analysed. The average values from technical literature are assigned to mechanical parameters without tuning or calibration. The maximum flooding on the opposite side of the valley and the peak flow rate of the discharge hydrograph through the dam section show good agreement with reference data and improvements with respect to published results. The validated derived model proves to be a promising engineering tool for quantifying the level of risk in analogous applications.

Optimization Simulation of Mooring System of Floating Offshore Wind Turbine Platform Based on SPH Method

ABSTRACTIn this paper, the Smoothed Particle Hydrodynamics method is used to simulate the dynamic response of the floating offshore wind turbine mooring system in a complex marine environment by using its advantages of dealing with free surface flow and fluid–structure interaction. The single‐cable mooring system and the double‐cable mooring system are introduced into the numerical simulation model of fluid–solid coupling interaction. The first‐order irregular wave and the second‐order regular wave are used to simulate different wave conditions. The operating state of the platform in these two cases is analyzed, and the accurate data such as the velocity change of the geometric center of the platform and the change of six degrees of freedom are obtained. Using visual processing and data analysis, it is found that the optimized double‐cable mooring system structure improves the vibration reduction ability of the platform.

Investigations of high-speed projectile impact on symmetric sandwich structures containing solid propellant with core perforations

The response of solid rocket motors (SRMs) to high-speed fragment impacts is crucial for their safety design and operational use in scenarios such as rocket launches and space applications. The visualized Burn to Violent Reaction (BVR) test is used to observe intense reactions induced by high-speed projectile impacts. Employing a two-stage light gas gun and optical diagnostic techniques including high-speed schlieren imaging and direct photography, the impact-induced deflagration/explosion behavior, and reaction growth behavior were investigated. The damage mechanisms of the casing and propellant samples were assessed, and the reaction growth and afterburn effects of the impact-induced fragment cloud were quantitatively analyzed. The results indicate that the ignition delay time is inversely correlated with the impact velocity, decreasing from ms to μs scale. Across a wide range of velocities (1050–2058 m/s), higher projectile velocities induce more sustained and vigorous combustion reactions within the propellant. Furthermore, increasing the propellant air gap to 7.8 cm does not trigger further reactions under the studied configurations. The reaction mechanisms are closely linked to the characteristics of the fragment cloud induced by the impact. The developed Smoothed Particle Hydrodynamics (SPH) method, incorporating material constitutive models, ignition criteria, and reaction growth models, was used to study the influence of projectile velocity on the reaction mechanisms. The simulation results were compared with experimental data, demonstrating satisfactory accuracy.

Investigations on the fracture mechanisms of Z-shaped fissured rock-like specimens

Complex shapes of cracks exist in natural rock masses, however, present research has simplified it into straight line-shaped fissures. In view of this, three-dimensional (3D) printing is employed to make Z-shaped fissured specimens with different main fissure angle α and secondary fissure angle β. The compress fracture experiments are conducted, and full-field strain distributions during crack propagations are obtained using Digital Image Correlation (DIC) technology. Traditional Smoothed Particle Hydrodynamics (SPH) method is improved to examine damage process as well as fracture mechanisms in Z-shaped fissured specimens. It can be concluded that: Wing Crack (WC), Main Crack (MC), Outer Crack (OC) and Inner Crack (IC) are observed in the experiment. The secondary fissure angle β guides the initiation of MC, while the main fissure angle α guides the initiation of WC. Stress–strain curve of 3D printing samples with Z-shaped fissures shows similar trends to that of real rock, experiencing four typical parts. Numerical results show high similarities with experimental results. We have also discussed the crack initiation mechanisms in various main fissure angle α and secondary fissure angle β in the end, and concluded the stress distribution characters. The findings of this research will offer some references for correct understanding of the crack evolution processes and fracture mechanics of Z-shaped fissured rock masses.

An algorithm for the incorporation of relevant FVM boundary conditions in the Eulerian SPH framework

The finite volume method (FVM) is widely recognized as a computationally efficient and accurate mesh-based technique. However, it has notable limitations, particularly in mesh generation and handling complex boundary interfaces or conditions. In contrast, the smoothed particle hydrodynamics (SPH) method, a popular meshless alternative, inherently circumvents the challenges of mesh generation and yields smoother numerical outcomes. Nevertheless, this approach comes at the cost of reduced computational efficiency. Consequently, researchers have strategically combined the strengths of both methods to investigate complex flow phenomena, producing precise and computationally efficient outcomes. However, algorithms involving the weak coupling of these two methods tend to be intricate and face challenges regarding versatility, implementation, and mutual adaptation to hardware and coding structures. Thus, achieving a robust and strong coupling of FVM and SPH within a unified framework is essential. A mesh-based FVM has recently been integrated into the SPH-based library SPHinXsys. However, due to the differing boundary algorithms between these methods, the crucial step for establishing a strong coupling of both methods within a unified SPH framework is to incorporate the FVM boundary algorithm into the Eulerian SPH method. In this paper, we propose a straightforward algorithm within the Eulerian SPH method, which is algorithmically equivalent to that in FVM and based on the principle of zero-order consistency. Moreover, several numerical examples, including compressible and incompressible flows with various boundary conditions in the Eulerian SPH method, demonstrate the stability and accuracy of the proposed algorithm.

Numerical investigation of spreading phenomena of molten corium using EISPH method

Understanding the behavior of molten corium is crucial for effective heat management and ensuring the integrity of reactor containment during severe nuclear incidents. Corium spreading is a complex multi-physics phenomenon influenced by hydrodynamics, heat transfer, and phase change. The Smoothed Particle Hydrodynamics (SPH) method is utilized to study corium flow, leveraging its ability to handle complex fluid dynamics and its compatibility with parallel computing architectures. This research examines two specific corium spreading cases: the VULCANO VE-U7 experiment, which is characterized by a wide mushy zone, and the FARO L26S experiment, noted for its narrow mushy zone. The study compares spreading lengths and temperature profiles over time with experimental data, offering a detailed analysis of the observed spreading behaviors. Variations in physicochemical properties result in distinct spreading patterns between the cases, highlighting the complexity of corium behavior under different scenarios. The findings demonstrate the applicability and capability of the SPH method in capturing various characteristics of corium spreading effectively.

Efficient smoothed particle hydrodynamics modeling of airtanker water dropping: From basic validations to practical applications

The water-dropping (by water-dropping, we mean the phenomenon of water flow dispersing into droplets under the influence of airflows) of airtankers (by airtankers, we mean the aircraft carrying out firefighting missions) has always been a challenge in computational fluid dynamics simulation due to its complex mechanism and vast splashing space. Although the smoothed particle hydrodynamics (SPH) method has advantages in dealing with splashing problems, the multiphase flow SPH model faces the challenge of low computational efficiency in simulating splashing problems in the vast space. An efficient SPH model considering airflow resistance based on the single-phase coupling algorithm between fluid particles and airflows is proposed in this paper. The SPH model can calculate the airflow resistance of fluid particles based on their windward surface and surface normal and then simulate the splashing trajectory and pattern of SPH particles under the influence of high-speed airflows. In this article, two benchmark cases, including water jet and dropped water in the wind, are simulated based the SPH model. The simulation results are consistent with experimental results, verifying the computational accuracy and efficiency of the proposed SPH model. After that, the entire pattern of water-dropping about an airtanker is simulated, proving the feasibility of the algorithm for simulating large-scale water-dropping engineering problems.

An improved smoothed particle hydrodynamics method for the coupled simulation of fixed net structures in currents and waves

In the present paper, a numerical model, named smoothed particle hydrodynamics (SPH)-net model, is proposed for the coupled simulation of fixed net structures in currents and waves based on the coupling between the SPH method and screen model. The fluid is solved by the SPH method and the net structures are handled by the screen model, both of which are represented by a number of Lagrangian particles. A coupling algorithm between the SPH method and screen model is derived based on the momentum disturbance, which allows for accurate simulation of interactions between net structures and fluid. Thanks to the quasi-static assumption of the screen model, the proposed model can both handle the net structures in currents and waves. To validate the SPH-net model, numerical simulations were conducted on three distinct cases: fixed net panels in currents, a fixed net cage in currents, and a fixed net panel in the regular wave. The comparison of hydrodynamic forces on the net between the numerical results and experimental data demonstrates that the proposed SPH-net model has accuracy and reliability in predicting the hydrodynamic forces acting on fixed net structures in currents and regular waves.

Hydrodynamization and resummed viscous hydrodynamics

In this paper, I review our current understanding of the applicability of hydrodynamics to modeling the quark–gluon plasma (QGP), focusing on the question of hydrodynamization/thermalization of the QGP and the anisotropic hydrodynamics (aHydro) far-from-equilibrium hydrodynamic framework. I discuss the existence of far-from-equilibrium hydrodynamic attractors and methods for determining attractors within different hydrodynamical frameworks. I also discuss the determination of attractors from exact solutions to the Boltzmann equation in relaxation time approximation and effective kinetic field theory applied to quantum chromodynamics. I then present comparisons of the kinetic attractors with the attractors obtained in standard second-viscous hydrodynamics frameworks and aHydro. I demonstrate that, due to the resummation of terms to all orders in the inverse Reynolds number, the aHydro framework can describe both the weak- and strong-interaction limits. I then review the phenomenological application of aHydro to relativistic heavy-ion collisions using both quasiparticle aHydro and second-order viscous aHydro. The phenomenological results indicate that aHydro provides a controlled extension of dissipative relativistic hydrodynamics to the early-time far-from-equilibrium stage of heavy-ion collisions. This allows one to better describe the data and to extract the temperature dependence of transport coefficients at much higher temperatures than linearized second-order viscous hydrodynamics.

NOTCH1 drives tumor plasticity and metastasis in hepatocellular carcinoma.

Liver cancer, the third leading cause of cancer-related mortality worldwide, has two main subtypes: hepatocellular carcinoma (HCC), accounting most of the cases, and cholangiocarcinoma (CAA). NOTCH pathway regulates the intrahepatic development of bile ducts, which are lined with cholangiocytes, but it can also be upregulated in 1/3 of HCCs. To better understand the role of NOTCH in HCC, we developed a novel mouse model driven by activated NOTCH1 intracellular domain (NICD1) and MYC overexpression in hepatocytes. Using the hydrodynamic tail vein injection method for establishing primary liver tumors, we generated a novel murine model of liver cancer harboring MYC overexpression and NOTCH1 activation. We characterized this model histopathologically as well as transcriptomically, utilizing both bulk and single cell RNA-sequencing. MYC;NICD1 tumors displayed a combined HCC-CCA phenotype with temporal plasticity. At early time-points, histology was predominantly cholangiocellular, which then progressed to mainly hepatocellular. The hepatocellular component was enriched in mesenchymal genes and gave rise to lung metastasis. Metastatic cells were enriched in the TGFB and VEGF pathways and their inhibition significantly reduced the metastatic burden. Our novel mouse model uncovered NOTCH1 as a driver of temporal plasticity and metastasis in HCC, the latter of which is, in part, mediated by angiogenesis and TGFß pathways.

NDUFS3 alleviates oxidative stress and ferroptosis in sepsis induced acute kidney injury through AMPK pathway

In recent years, ferroptosis has been found to play an important role in various acute kidney injury (AKI). However, relatively little research has been conducted on sepsis-induced acute kidney injury (SI-AKI). As an important trigger of ferroptosis, how mitochondrial damage plays a regulatory role in SI-AKI is still unclear. To explore the potential relationship between mitochondria and ferroptosis, we established a SI-AKI rat model by intraperitoneal injection of lipopolysaccharide (LPS). Transcriptome sequencing was used to detect changes in gene transcription levels in the control group, LPS 3 h group, LPS 6 h group and LPS 12 h group. The severity of kidney injury was determined based on serum creatinine (CRE), blood urea nitrogen (BUN), tissue HE staining, TUNEL staining and inflammatory factor levels. Cytoscape software was utilized to screen several mitochondria-related HUB genes, and NADH dehydrogenase [ubiquinone] ferrithionein 3 (NDUFS3) was selected for subsequent validation due to its novelty and feasibility. qRT-PCR, Western blot was employed to evaluate the expression of NDUFS3 in kidney tissues. GO enrichment analysis revealed that up-regulated genes in the LPS 12 h group were enriched in several cell death terms while down-regulated genes were enriched in lipid metabolic process and oxidation–reduction progress terms. Furthermore, Western blot, IHC, MDA, GSH and iron content levels were used to assess ferroptosis in the kidney tissue of the SI-AKI rats, dihydroethidium (DHE) assay and ATP kit were used to assess mitochondrial ROS levels and mitochondrial function. To further validate the function of NDUFS3, we constructed overexpression rats using hydrodynamic method by tail vein injection of pc DNA3.1-NDUFS3 overexpression plasmid. we utilized LPS to stimulate HK-2 cells and establish an in vitro model. We then overexpressed NDUFS3 using pcDNA 3.1. The overexpression of NDUFS3 was found to inhibit LPS-induced ferroptosis and mitochondrial damage in HK-2 cells, as evidenced by Western blot, MDA, GSH, divalent iron, ROS levels, Mitosox red, ATP content and transmission electron microscopy. Finally, the use of Compound C to inhibit AMPK in HK-2 cells demonstrated that NDUFS3 plays a protective role through the AMPK pathway. Therefore, our study supports the emerging role of NDUFS3 in SI-AKI, providing new potential mitochondria-related targets for the treatment of SI-AKI.

Modeling multiple-pipe failures in stormwater networks using graph theory

ABSTRACT One way to enhance the resilience of urban stormwater networks is to identify critical components of the network for targeted management and maintenance strategies. However, tackling multiple-pipe failures poses a significant hurdle due to the computational burden of conventional methods, making it impractical to analyze all potential combinations of pipe failures. To address this research gap, this study proposes a novel method based on complex network analysis to determine critical pipe failure combinations. The method incorporates network topology and estimates flooding impacts based on graph measures instead of solving complex hydraulic equations. The method is tested on two case studies with varying loop degrees and for different failure levels and compared with the state-of-the-art hydrodynamic modeling method (HMM) in terms of accuracy and computational time. Results show that the proposed graph theory method (GTM) can be used to identify the most critical pipe failure combinations. However, the accuracy of the GTM decreases slightly with increasing failure level and with increasing loop degree of the network. A hybrid graph-hydrodynamic model (GHM) is also developed as part of the study which combines advantages from both GTM and HMM.