Hydrodynamics Algorithm Research Articles

Numerical Simulation Study on Ice–Water–Ship Interaction Based on FEM-SPH Adaptive Coupling Algorithm

To address the impact of layered ice and seawater on polar vessels navigating in icy waters, this study employs a coupled finite element method (FEM) and smoothed particle hydrodynamics (SPH) algorithm to simulate the collision dynamics between the bow and stern of a designated icebreaker and the ice layers. The foundational principles and deployment strategies of the coupling algorithm have been meticulously delineated, with a subsequent simulation conducted to model the trajectory of icebreakers navigating through stratified ice conditions. The ice load on the hull, the movement of broken ice bodies, and the temporal variation of ice resistance during collision were analyzed. The method’s applicability and precision were substantiated through a comparative analysis between the simulated ice resistance outcomes and the ice load estimations derived from the Lindqvist formula. Finally, the differences between the bow and stern icebreaking methods were compared. The research findings indicate that the coupling algorithm demonstrates high precision in simulating the navigation of icebreakers under layered ice conditions, aligning with actual scenarios. This provides a solid foundation for further exploration of the ice load on polar vessels. Furthermore, at equivalent speeds and ice thicknesses, stern icebreaking was observed to induce greater oscillations in ice load and yield a higher mean resistance compared to bow icebreaking.

Simulating Nonlinear Radiation Diffusion Through Quantum Computing

The recent success of the fusion ignition experiment at Lawrence-Livermore National Laboratory has renewed excitement for inertial confinement fusion. Designing such experiments relies on computational modeling using radiation hydrodynamic codes run on massively parallel supercomputers which simulate hydrodynamic flows, radiation diffusion, and thermonuclear burn. Constructing a quantum algorithm for radiation hydrodynamics that provides a quantum speedup is of great interest. A recent quantum algorithm that solves the Navier-Stokes equations of hydrodynamics with a quadratic speedup marks a first step towards this goal. Here we take the next step and present a quantum algorithm for nonlinear radiation diffusion that also has a quadratic speedup. To verify the algorithm we consider radiation striking a cold, optically thick target that generates a Marshak wave in the target. Results of numerical simulation of the quantum algorithm are compared with those of a standard partial differential equation solver and excellent agreement is found.

Reliability analysis using Limit equilibrium and Smoothed Particle Hydrodynamics-based method for homogeneous soil slopes.

This paper develops a combined method to predict the volume of sliding mass for homogeneous slopes in an efficient manner. Firstly, the failure surface with minimum factor of safety (FS) in Limit Equilibrium Method is equated to that one determined by Smoothed Particle Hydrodynamics algorithm to obtain the threshold displacement value for unstable and stable particles. Secondly, the threshold displacement value is used to identify the volume of sliding mass using SPH. Finally, a regression model is developed based on a finite number of SPH simulations for homogeneous soil slopes. The proposed LEM-SPH based method is illustrated through a cohesive soil slope. It is concluded that the use of failure surface with minimum FS in LEM tends to underestimate the volume of sliding mass and to give an unconservative risk value. The Coefficient of Variation (Cov) of volume of sliding mass are 0.14, 0.28, 0.4, 0.48, 0.53 for Cov of soil properties = 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. The uncertainty of soil properties has a significant effect on the mean value of volume of sliding mass and therefore the landslide risk value. The proposed method is necessitated for cases where large uncertainties in soil properties exist.

High efficiency integrated urban flood inundation simulation based on the urban hydrologic unit

As the impact of flooding intensifies globally in metropolitan areas, there is an urgent need for high-resolution flood forecasting models to facilitate preparedness and mitigate flood impacts. In response, we have proposed a high efficiency algorithm (HEA) designed to simulate urban flood inundation, leveraging the urban hydrologic unit (UHU) concept from an urban hydrological cycle perspective. The HEA significantly reduces the computational demands associated with high-resolution modeling by using a hydrologic unit derived from the digital elevation model (DEM). This approach effectively shifts the overwhelming burden of computational load to the hydrodynamic algorithm (HDA), which is grounded in the Shallow Water Equations (SWEs), thus enabling efficient flood inundation simulation crucial for time-critical decision making during extreme events. Our research also incorporated the HEA and HDA methods into a self-developed, distributed-framework basin modeling system, named the Taihu Basin Model (TBM). Both the HEA and HDA models were calibrated and validated with observed data on pipe level, flow rate, and inundation depth from our Shuangqiaobang experimental fields. Comparative analysis, focusing on simulated urban flood inundation distribution characteristics, simulation accuracy and timeliness, demonstrated the superior effieicney of the HEA method by three orders of magnitude. The consistency between observed data and the simulated results of both HEA and HDA models underscores the accuracy and reliablility of these models. The HEA model’s simulated urban flood inundation distribution appears more patchy and localized compared to the HDA model, due to the generalization of urban UHUs in the TBM.

Stream-disk shocks as the origins of peak light in tidal disruption events.

Tidal disruption events (TDEs) occur when stars are ripped apart1,2 by massive black holes and result in highly luminous, multi-wavelength flares3-5. Optical-ultraviolet observations5-7 of TDEs contradict simple models of TDE emission2,8, but the debate between alternative models (for example, shock power9,10 or reprocessed accretion power11-16) remains unsettled, as the dynamic range of the problem has so far prevented ab initio hydrodynamical simulations17. Consequently, past simulations have resorted to unrealistic parameter choices10,12,18-21, artificial mass injection schemes22,23 or very short run-times24. Here we present a three-dimensional radiation-hydrodynamic simulation of a TDE flare from disruption to peak emission, with typical astrophysical parameters. At early times, shocks near pericentre power the light curve and a previously unknown source of X-ray emission, but circularization and outflows are inefficient. Near peak light, stream-disk shocks efficiently circularize returning debris, power stronger outflows and reproduce observed peak optical-ultraviolet luminosities25,26. Peak emission in this simulation is shock-powered, but upper limits on accretion power become competitive near peak light as circularization runs away. This simulation shows how deterministic predictions of TDE light curves and spectra can be calculated using moving-mesh hydrodynamics algorithms.

Investigations on geopolymer-based seawater sea-sand high performance concrete slabs reinforced with basalt FRP bars under direct contact explosions

Adopting locally available raw materials like seawater and sea-sand in coastal areas and oceanic islands has facilitated meeting the demands of marine engineering. However, these raw materials contain corrosive elements that could threaten the steel reinforcement in concrete structures, thus non-corrosive fibre-reinforced polymer (FRP) bars are proposed. In the present study, the geopolymer-based seawater sea-sand high performance concrete (G-SHPC) slab reinforced with basalt FRP bars was designed to preliminarily evaluate its dynamic behaviour under contact explosions. Tests were conducted on three large-sized slabs with different TNT charge weights, including 0.8 kg, 1.6 kg and 2.2 kg. To complement the experimental investigation, a numerical simulation was then performed in ANSYS-DYNA. A Continuous Surface Cap (CSC) model was developed to accommodate the unique characteristics of G-SHPC. Two different blast modelling methods, including the Arbitrary Lagrangian-Eulerian (ALE) algorithm and a hybrid Finite-Element (FE) and Smooth Particle Hydrodynamics (SPH) algorithm, were examined to faithfully reproduce the contact explosion phenomena. The structural models considered the bond-slip behaviour, and three bond-slip models were compared. The numerical results obtained through the ALE algorithm and the beam-in-solid bond-slip model exhibited fair agreement with the test results, with a maximum error of less than 6.3%. A parametric study was further conducted to establish the damage identification diagram. Formulas based on empirical data were formulated to anticipate the damage degrees of G-SHPC slabs exposed to contact explosions.

Dynamic Topology Optimization of Constrained Layer Damping Structure Considering Non-Uniform Blast Load

The non-uniform distributed pressure of impact wave is usually simplified into concentrated or uniform load equivalently in the optimization design of constrained layer damping structure. However, for the thin-walled structure, it becomes necessary to regard the load as a non-uniform distribution. In this paper, a topology optimization approach is proposed considering the blast load with non-uniform distribution, aiming to unveil its impact on optimization layouts and dynamic responses. Initially, the smoothed particle hydrodynamics (SPH) algorithm is used to obtain the blast pressure what are extracted and integrated into the optimization model. Subsequently, the relative density is regarded as design variable. The construction of material penalty model and the topology optimization model are based on polynomial interpolation scheme (PIS). The sensitivity of objective function is deduced employing an improved adjoint variable method (AVM) to fit the load forms, and the Newmark-[Formula: see text] method is used to calculate the dynamic response. The optimization criterion (OC) is adopted to update the design variables. Finally, two numerical examples are used to exhibit the validity and accuracy of the presented methodology. The findings indicate that the distributed form, spread velocity, excited position and excited amplitude of the blast load all exert a notable influence on optimization results and dynamic response. These results underscore the valuable engineering application of this research and introduce a fresh perspective to the challenge of topology optimization under the blast case.

Multiscale Smoothed Particle Hydrodynamics based on a domain-decomposition strategy

A multi-resolution algorithm for weakly-compressible Smoothed Particle Hydrodynamics is hereby proposed. The approach chosen is based on a domain decomposition to subdivide the computational domain into regions with different resolutions. Each sub-problem is closed by appropriate Dirichlet boundary conditions that are enforced via buffer regions, populated by particles whose physical quantities are obtained by means of an interpolation over adjacent sub-domains.The algorithm has been implemented into the DualSPHysics open-source code and it has been tested and validated through a series of different study cases. The capability of the numerical scheme to simulate multiscale fluid flow has been demonstrated by solving the flow past a cylinder for a Reynolds number of 9,500 and a ratio between the largest and smallest particle size equal to 28. Furthermore, the proposed SPH multi-resolution algorithm can also be used for flow around moving objects, such as an oscillating cylinder in cross-flow, and free-surface flow, such as the simulation of a triangular wedge impacting on the free surface of a quiescent liquid.

Numerical simulations for largely deformed beams and rings adopting a nontensile smoothed particle hydrodynamics algorithm

Three typical elastic problems, including beam bending, truss extension and compression, and two-rings collision are simulated with smoothed particle hydrodynamics (SPH) using Lagrangian and Eulerian algorithms. A contact-force model for elastic collisions and equation of state for pressure arising in colliding elastic bodies are also analytically derived. Numerical validations, on using the corresponding theoretical models, are carried out for the beam bending, truss extension and compression simulations. Numerical instabilities caused by largely deformed particle configurations in finite/large elastic deformations are analysed. The numerical experiments show that the algorithms handle small deformations well, but only the Lagrangian algorithm can handle large elastic deformations. The numerical results obtained from the Lagrangian algorithm also show a good agreement with the theoretical values. doi: 10.1017/S1446181123000160

Parametric sensitivity of crane ship numerical model with experimental verification in a wave basin

Numerical modeling of crane ship dynamics has become widely used with the development of computational fluid dynamics methods. However, the high number of components in the hydrodynamic forces calculation algorithm introduces a degree of uncertainty, so researchers face difficulties in assessing the influence of various force contributions and model parameters on the result. In this regard, the authors of this paper investigate the parametric sensitivity of a reduced-scale crane ship numerical model. The study should provide some insight for research engineers on how the dynamics of the vessel visually change when different approaches to force calculations, mesh sizes, and cable modeling are taken into account. It would also facilitate optimized model creation for marine engineers since it is not always possible to perform the determination of all the terms of a complex multiphysics model. The comparison of simulation results with the wave-basin experiments on the determination of ship wave-induced motions accompanies the authors’ conclusions.

Hydrodynamic Model of Hydraulic Engineering Based on Trigonometric Function Relation Equation

Abstract In order to explore the application of fluid mechanics technology in water conservancy and hydropower stations, the author proposes the study of hydraulic engineering fluid mechanics model based on trigonometric function relationship equation. According to standard k- ε Double equation and Reynolds time average (N-S) equation, given the runner boundary conditions, establish the mathematical model of the internal flow of the hydraulic turbine. Through CFD simulation technology, the runner of hydraulic turbine is numerically simulated to obtain the velocity distribution and blade pressure distribution inside the runner, movable guide vane and fixed guide vane, the reliability of the design is improved, and the application of CFD technology in hydropower project is analyzed with an example. The results show that, when the diameter of guide vane distribution circle is 4760mm, the scheme is optimal, and the relative efficiency under the optimal working condition is 96.35%. The flow of the modified runner from the inlet of the volute to the outlet of the draft tube is very stable under the optimal working condition, and there is no obvious vortex, especially there is no obvious vortex belt and vortex at the outlet of the runner; There is no obvious vortex in the draft tube, the flow on both sides of the pier is very uniform, and the flow on one side is not significantly greater than that on the other side, which fully shows that the flow performance of the modified runner is good. After reconstruction, the runner outlet flow field is good, and the internal flow line of the draft tube is smooth. The application prospect of hydrodynamic algorithm for hydraulic engineering is relatively broad.

Coupled FEM-SPH simulation of the protective properties for metal/ceramic composite armor

To support the structural optimization design of metal-ceramic armor against penetration protection performance, this paper optimizes the armor in terms of protection material, armor structure, and bullet resistance mechanism, and envisages a new metal-constrained ceramic composite armor, which overcomes the disadvantages of ceramic material fragility. A coupled finite element-smooth particle hydrodynamics (FEM-SPH) algorithm is used to simulate the penetration process, and the influence of ceramic unit shape and size on the armor protection performance is investigated by quantitatively comparing the bullet energy loss, velocity change, penetration depth, and other indicators that reflect the ballistic protection mechanism. The results show that metal-confined ceramic armor has repairable performance, and filling ceramic units can reduce armor failure area, save armor repair time, and extend armor service life. When the velocity of the projectile is less than 500 m/s, the damaged area of the armor filled with small-sized unit ceramics (1/4 bullet caliber) is small and easy to repair; when the velocity of the projectile is greater than 500 m/s, the armor filled with large-sized unit ceramics (2 times the bullet caliber) can effectively increase the bullet residence time and improve the armor's resistance to elasticity. The results of this paper can provide a reference for the optimal design of the armor structure.

Comparing methods for permeability computation of porous materials and their limitations

AbstractEfficient numerical simulations of fluid flow on the pore scale allow for the numerical estimation of effective material properties of porous media, e.g. intrinsic permeability or tortuosity. These parameters are essential for various applications where hydro‐mechanical properties on larger scales have to be known. Numerical tools based intrinsically on pore scale simulations are known e.g. as Digital Rock Physics in geosciences and have even more and more replaced physical experiments. For these reasons, the validation of numerical methods as well as the establishment of clear limits regarding the application areas play an important role. Here, we compute single‐phase flow through a porous matrix, e.g. irregular sphere packings, sandstones, artificially created thin porous media, on the pore scale. Therefore we implement on the one hand a Smoothed Particle Hydrodynamics algorithm for solving the Navier‐Stokes equations and on the other hand a Finite Difference solver for the Stokes equations. Both methods work directly and seamlessly on voxel data of porous materials which are generated by µXRCT‐scans or by microfluidic experiments that have undergone segmentation and binarization. We compare both solvers from a parallel performance point of view as well as their results for flows in the Darcy regime. In addition, we investigate the limitations of the solvers using the example of a porous material whose pore geometry changes over time and precipitation affects the flow conditions.

An entropy-stable updated reference Lagrangian smoothed particle hydrodynamics algorithm for thermo-elasticity and thermo-visco-plasticity

This paper introduces a novel upwind Updated Reference Lagrangian Smoothed Particle Hydrodynamics (SPH) algorithm for the numerical simulation of large strain thermo-elasticity and thermo-visco-plasticity. The deformation process is described via a system of first-order hyperbolic conservation laws expressed in referential description, chosen to be an intermediate configuration of the deformation. The linear momentum, the three incremental geometric strains measures (between referential and spatial domains), and the entropy density of the system are treated as conservation variables of this mixed coupled approach, thus extending the previous work of the authors in the context of isothermal elasticity and elasto-plasticity. To guarantee stability from the SPH discretisation standpoint, appropriate entropy-stable upwinding stabilisation is suitably designed and presented. This is demonstrated via the use of the Ballistic free energy of the coupled system (also known as Lyapunov function), to ensure the satisfaction of numerical entropy production. An extensive set of numerical examples is examined in order to assess the applicability and performance of the algorithm. It is shown that the overall algorithm eliminates the appearance of spurious modes (such as hour-glassing and non-physical pressure fluctuations) in the solution, typical limitations observed in the classical Updated Lagrangian SPH framework.

Research on non-cohesive jet formed by Zr-based amorphous alloys

The shaped charge jet formation of a Zr-based amorphous alloy and the applicability of different numerical algorithms to describe the jet formed were experimentally and numerically investigated. X-ray experiments were performed to study jet characteristics. The numerical results for the Zr-based amorphous alloy jet formed via the Euler and smooth particle hydrodynamics (SPH) algorithms were compared and analyzed using the Autodyn hydrocode. Particle motion was examined based on material properties. The Zr-based amorphous alloy formed a noncohesive jet driven by an 8701 explosive. Both the Euler and SPH algorithms achieved high accuracy for the determination of jet velocity. When the improved Johnson-Holmquist constitutive model (JH-2) was used, numerical results confirmed the model’s suitability for the Zr-based amorphous alloy. The Euler algorithm effectively reflected jet shape within a short computing time, whereas the SPH algorithm was highly suitable for showing the shape of the jet tail within a long computing time. In the 3D Euler model, the flared jet mouth indicated radial particle dispersion; however, in the 2D model, particle dispersion in the head was directly observed by using the JH-2 material model. The brittle fracture of the material reduced the proportion of particles near the liner apex forming a jet. Furthermore, a new method in which stagnation pressure was used to predict jet formation and its coherence was proposed since the collapse angle was difficult to obtain.

An improved multiphase SPH algorithm with kernel gradient correction for modelling fuel–coolant interaction

Fuel–coolant interaction (FCI) has a pivotal role in the development of core disruptive accident in a sodium-cooled fast reactor. The drastic deformation of multiphase interface in the FCI is hard to deal with in the traditional grid method. In this paper, an improved multiphase smoothed particle hydrodynamics (SPH) algorithm corrected with the kernel gradient correction (KGC) technique is presented for multiphase flow with a large density ratio and complex interfacial behaviors. The density discontinuity across the multiphase interface is described with the use of special volume, which only depends on the position information of adjacent particles. This multiphase SPH algorithm, which is troubled by an unstable and mixed-interface problem under a large density ratio, is significantly improved with the KGC technique. The accuracy and robustness of the improved method are demonstrated in the numerical simulations of the deformation of a square droplet, Rayleigh–Taylor instability, and bubble rising in water. The verified corrected multiphase SPH is applied to simulate the hydrodynamic behaviors of the general FCI and the interaction between fuels coated with stainless steel film and coolant. Boundary layer stripping, Rayleigh–Taylor instability, and Kelvin–Helmholtz instability are observed as important mechanisms of hydraulic fracturing. The fragments’ distribution and the influence of stainless steel film are analyzed. The existence of a stainless steel film has been shown to inhibit breakage.

Viscous Damping Performance Analysis and Prediction of Axisymmetric Cylindrical Oscillating Buoys With Different Geometrical Configurations

Abstract With the intensification of the world's energy demand, clean and efficient marine energy has received more attention, and energy conversion devices are particularly important. As an important part of the oscillating wave energy conversion device, the hydrodynamic characteristics of cylindrical absorbers have a great impacton wave energy conversion efficiency. When cylindrical buoys with different bottom configurations heave under the action of waves, the oscillating motion and flow field become more complex. At present, potential flow theory is usually used to predict the motion response of cylindrical buoys in waves. Although the calculation speed is fast, there will be large errors due to the lack of consideration of the effect of fluid viscosity. To explore this error range, a three-dimensional numerical wave pool is established based on the viscous fluid theory and STARCCM+ software to study the response of buoy and wave coupling action considering the viscous effect. At the same time, based upon the potential flow theory, the analytical solution of the cylindrical buoy oscillating in waves is established. Combined with the computational fluid dynamics numerical simulation results, the oscillation laws of the buoys with different bottom configurations in waves with different periods are compared, and the effects of viscosity on the buoys' motion are also explored. According to the calculation results of floating buoy movement under viscous and nonviscous fluid, the statistical correction algorithmis adopted to obtain the viscous hydrodynamic correction algorithm of floating buoy movement based on the potential flow theory, and the feasibility is verified by viscous numerical simulation under other wave periods.

Experimental and numerical studies of fragmentation shells filled with advanced HMX-plastic explosive compared to various explosive charges

The wide usage of TNT as a main charge for fragmentation shells has been eliminated due to its lower performance and exudation on the fuze thread and relevant safety measures inconvenience. These disadvantages have not become accepted anymore due to the desired safety requirements and the limited efficiency of the TNT, especially when different new explosives are introduced into researches. This research studies the fragmentation calculations of the 120 mm high explosive shell when its is loaded with different explosives rather than TNT. Different explosives have been used in the current research include the melt cast compositions such as Octol and composition B, a cast cured composition based on RDX with HTPB polymer matrix and the plastic explosive composition HMX-silicone. The fingerprint of the fragmentation pattern of each shell loaded with different explosive has been obtained using Autodyn smooth particle hydrodynamic (SPH) algorithm, whose numerical model has been validated with previous measurements using TNT explosive. Based on obtained numerical estimates, the HMX-silicone explosive has been proposed to replace the traditional TNT explosive material. This explosive has been then manufactured and casted into the studied 120 mm shell, where the experimental field pit test was established to collect, separate and analyse the resultant fragments. Current calculations and experimental results showed that the shell loaded by composition HMX-silicone produced the highest fragmentation velocities (i.e. 1.5 times that of TNT) and the largest number of fragments (i.e. 2.7 times that of TNT) with lower masses, which will be recommended for our next production stages instead of the traditional TNT.

A Combined O/U-Tube Oscillatory Water Tunnel for Fluid Flow and Sediment Transport Studies: The Hydrodynamics and Genetic Algorithm

This study proposes an oscillatory water tunnel (O/U-tube) equipped with two impellers to drive flows. The O/U-tube consists of two modes: U-tube mode and O-tube mode. The former can generate oscillatory flow, while the latter can produce both oscillatory and unidirectional flows with velocities up to 1.6 m/s. The hydrodynamics of the U-tube and O-tube modes were examined analytically. For the U-tube mode, a sine-varying rotational speed for the impeller caused higher harmonic components for the velocity, owing to the local inertia and gravity forces. In the steady state of the O-tube mode, owing to the resistance force, the flow velocity was proportional to the rotational speed. To generate the target flow conditions, two open-loop control schemes were proposed according to the analytic approach for the U-tube mode and a genetic algorithm for the O-tube mode. The analytic approach was based on a hydrodynamic model with a given flow condition. In the genetic algorithm, the rotational speed was represented by a square root of the Fourier series. The optimal coefficients of the Fourier series to generate the target flow were determined by using the genetic algorithm and the hydrodynamic model. Both approaches were experimentally validated. Consequently, the O/U-tube with the open-loop schemes can be used to generate the desired oscillatory and unidirectional flows.

Dynamical response of a floating plate to water waves using a smoothed particle hydrodynamics algorithm for nonlinear elasticity

In this work, a newly developed Smoothed Particle Hydrodynamics (SPH) algorithm for nonlinear elasticity is combined with an incompressible SPH fluid solver to investigate the dynamics of a floating plate under impacts of regular water waves with a high steepness. Two scenarios of the plate's rigidity are investigated. The simulation results show that deformations of the stiffer plate mainly occur in a simple bending mode with small amplitudes, and the plate is almost submerged by a strong fluid flow over its surface. In the other scenario, the plate deforms more complexly with much higher deformation amplitudes but experiences a much weaker overwash. The more flexible plate is less resistant to wave motions and converts more wave energy into elastic deformations, and therefore, the overwash is less severe. A strong overflow exerts a pressure force onto the plate that alters the plate's dynamics and adds a viscous (damping) effect on the plate's elastic vibrations, especially in high-frequency modes. A rigorous examination of the numerical convergence and validation using the linear thin plate theory is also carried out. The new SPH algorithm for nonlinear elasticity shows its stability and reliability in evaluating finite and large elastic deformations. Therefore, it is promising for simulating elastic structures in fluid–structure interaction problems.