Showing papers by "A-Man Zhang published in 2021"
TL;DR: Sun et al. as mentioned in this paper combined the multi-resolution δ + -SPH scheme and a total Lagrangian SPH method for more complex three-dimensional (3D) Fluid Structure Interaction (FSI) problems.
90 citations
TL;DR: In this article, a near-field underwater explosion simulation was carried out by coupling the SPH and RKPM solvers, in which the fluid solver is established based on the compressible SPH method, while the dynamic response of the structure is calculated based on RkPM shell formulation.
34 citations
22 citations
TL;DR: In this article, an experimental investigation of the dynamic properties of underwater explosion (UNDEX) bubble pairs produced with a range of phase differences is presented, defined as 2π(t1−t2)/Tosc, where ti (i) represents the bubble inception moment and Tosc is the experimentally obtained first period of a single UNDEX bubble.
Abstract: This study presents an experimental investigation of the dynamic properties of underwater explosion (UNDEX) bubble pairs produced with a range of phase differences Δθ, defined as 2π(t1−t2)/Tosc, where ti (i = 1,2) represents the bubble inception moment and Tosc is the experimentally obtained first period of a single UNDEX bubble. Each bubble was generated by a spherical hexogen explosive charge detonated in a cubical tank and observed via high-speed photography. The phase difference was adjusted by setting different delays between the two detonations, with an accuracy of 1.0 ms. Experiments were conducted with both horizontally and vertically positioned bubble pairs and with single bubbles as well. UNDEX bubble pairs are subject to a larger buoyancy effect than cavitation or spark-generated bubble pairs. The resultant bubble behavior in the bubble–bubble interaction is more complex and is yet to be understood. In our experiments, various bubble parameters, including bubble pulsation periods, bubble elongation ratios, and collapse-induced shock wave pressures bubble, were measured and studied. Dependence of the bubble dynamics on Δθ was found, demonstrating the significant influence of Δθ on the morphology and shock wave pressure of bubble pairs. The findings suggest a method of strengthening or weakening the damage potential of an UNDEX bubble pair based on the proper adjustment of the delay between two detonations. It may also lead to a better understanding of the dynamics of interacting bubbles with buoyancy effects.
20 citations
TL;DR: In this article, a comparative study of nonlocal differential operators is conducted for evaluating the computational performances of these two types of differential operators, and the results show that the second type of non-local differential operator is more suitable to deal with complex crack branching patterns than the first type of differential operator.
Abstract: In recent years, two types of nonlocal differential operators and their theories and formulations have been proposed and used in numerical modeling and computations, particularly simulations of material and structural failures, such as fracture and crack propagations in solids. Since the differences of these nonlocal operators are subtle, and they often cause confusion and misunderstandings. The first type of nonlocal differential operators is derived from the Taylor series expansion of nonlocal interpolation, e.g., Bergel and Li (Comput Mech 58(2):351–370, 2016), Madenci et al. (Comput Methods Appl Mech Eng 304:408–451, 2016) and Ren et al. (Comput Methods Appl Mech Eng 358:112621, 2020). The second type of nonlocal operators is based on the nonlocal operator theory in peridynamic theory, which is a class of antisymmetric nonlocal operators stemming from the nonlocal balance laws, e.g., Gunzburger and Lehoucq (Multiscale Model Simul 8(5):1581–1598, 2010) and Du et al. (SIAM Rev 54(4):667–696, 2012; Math Models Methods Appl Sci 23(03):493–540, 2013a). In this work, a comparative study is conducted for evaluating the computational performances of these two types of nonlocal differential operators. It is found that the first type of nonlocal differential operators can yield convergent results in both uniform and non-uniform particle distributions. In contrast, the second type of nonlocal differential operators can only converge in uniform particle distributions. Specifically, we have evaluated the performance of the two types of nonlocal differential operators in three crack propagation simulation examples. The results show that the second type of nonlocal differential operators is more suitable to deal with complex crack branching patterns than the first type of nonlocal differential operators, and the simulation results obtained by using the second type of nonlocal differential operators have better agreement with experimental observations. For modelings of simple crack growth and conventional elastic deformation problems, both nonlocal operators can provide good results in simulations.
20 citations
TL;DR: In this article, a particle regeneration technique is developed for smoothed particle hydrodynamics (SPH), where the fluid particles replaced by the background particles when the fluid density changes to a specific limitation.
19 citations
TL;DR: Several numerical tests show that the proposed WENO-SPH method is robust and able to accurately capture shockwaves, and benefiting from the low-dissipation property, it also has a good performance in resolving small-scale structures in flows.
17 citations
TL;DR: In this article, the tensile instability induced by negative pressures in Smoothed Particle Hydrodynamics (SPH) simulations is removed and new modifications for the Tensile Instability Control (TIC) and Particle Shifting Technique (PST) are proposed to simulate Fluid-Structure Interaction (FSI) phenomena with violent free-surface evolutions.
17 citations
TL;DR: Wang et al. as discussed by the authors proposed an improved solid boundary treatment technology that combines the dummy particle boundary and the normal flux method to simulate the water entry of a lifeboat in 3D complex geometries.
16 citations
TL;DR: In this paper, a high-speed camera and an acceleration sensor were used to investigate the cavity evolution and impact loads of high speed oblique water entry of high velocity high-energy projectiles.
15 citations
TL;DR: In this article, a nonlocal geometrically-exact shell theory and its computational formulation are developed, which can model fracture and crack growth in shell structures under finite deformations.
TL;DR: In this article, a 3D multi-fluid model is established based on the Eulerian finite element method and the adaptive mesh refinement technique to investigate the bubble evolution and its toroidal motion near a solid vertical wall.
TL;DR: An axisymmetric numerical model is established using the Eulerian Finite Element Method (EFEM) and the Volume of Fluid (VOF) method in dealing with the interface as discussed by the authors.
TL;DR: The computation results show that the newly-developed updated Lagrangian particle hydrodynamics (ULPH) method has the ability to simulate the complex solid object water entry precess accurately.
Abstract: Solid object water entry is a common problem in various natural, industrial and military applications, which involves large deformation of free surfaces and violent fluid–structure interactions. In computational fluid dynamics (CFD), this is a type of problem that tests the robustness and capacity of any CFD numerical algorithm. In this work, the newly-developed updated Lagrangian particle hydrodynamics (ULPH) method, which is a fluid version of peridynamics, is enhanced and applied to simulate solid object water entry problems. ULPH method is Lagrangian meshfree particle method that can ensure the specific free surface conditions automatically satisfied. The density filter and artificial viscosity diffusion are adopted in the ULPH scheme to stabilize and smooth the pressure field. In the process of a rigid body entering water, it may induce negative pressure in some areas of impact region, which can cause spurious tensile instability in some meshfree particle simulations, such as SPH and ULPH. A tensile instability control technique based on the ULPH framework has been developed to overcome the numerical instability. To validate the stability and accuracy of the ULPH approach in simulating water entry problems, several 2D and 3D examples of water entry have been carried out in this work. The necking and cavity pinch-off phenomena are visible in the numerical results. The simulation results of the ULPH method are well compared with experimental data and other numerical solutions. The water crown, cavity shapes and stream pattern formed around the rigid body entering the water can be well captured. The computation results show that the ULPH method has the ability to simulate the complex solid object water entry precess accurately.
25 Jan 2021
TL;DR: In this article, a three-dimensional fully coupled model was developed to investigate the interaction between a bubble and an elastic-plastic thin-walled plate, which can accurately calculate the bubble loading acting on the plate surface and describe the structural motion coupling with the flow field on two sides of the plate.
Abstract: On the basis of the boundary element method and explicit finite element method, a three-dimensional fully coupled model is developed to investigate the interaction between a bubble and an elastic-plastic thin-walled plate. The model can accurately calculate the bubble loading acting on the plate surface and describe the structural motion coupling with the flow field on two sides of the plate. As a result of the elastic-plastic effects of the thin-walled plate, the bubble displays attractive motion, repulsive motion, or splitting.
TL;DR: A novel cell-centered indirect Arbitrary-Lagrangian-Eulerian (ALE) discontinuous Galerkin (DG) scheme on moving unstructured triangular meshes with mesh topological adaptability aimed to deal with the strong distortions and large deformation flow problems.
TL;DR: Both the Euler equation and the level-set equation are discretized with the RKDG method which is compact and of high-order accuracy to simulate compressible two-medium problems with the Runge-Kutta discontinuous Galerkin (RKDg) method.
TL;DR: In this paper, the authors investigated the bubble behavior during multiple-bubble interaction and the resultant damage effect, especially the shock wave and its damage to ice, and showed that the damaging effect of bubbles can be affected by bubble-bubbles and bubble-boundary interaction and thus manipulated in such ways when needed.
TL;DR: In this article, a shock-capturing scheme based on smoothed particle hydrodynamics (SPH) is proposed to investigate strongly compressible flows with strong discontinuities in nature and engineering applications.
TL;DR: In this article, a multiphase Riemann-SPH model is developed to investigate water entry problems, and a special treatment, a cut-off value for the particle density, is arranged to avoid the occurrence of negative pressure.
Abstract: The water entry is a classic fluid-structure interaction problem in ocean engineering. The prediction of impact loads on structure during the water entry is critical to some engineering applications. In this paper, a multiphase Riemann-SPH model is developed to investigate water entry problems. In this model, a special treatment, a cut-off value for the particle density, is arranged to avoid the occurrence of negative pressure. A remarkable advantage of the present multiphase SPH model is that the real speed of sound in air can be allowed when simulating water-air flows. In the present work, considering the air effect, several typical water entry problems are studied, and the evolution of multiphase interface, the motion characteristic of structure and complex fluid-structure interactions during the water entry are analyzed. Compared with the experimental data, the present multiphase SPH model can obtain satisfactory results, and it can be considered as a reliable tool in reproducing some fluid-structure interaction problems.
TL;DR: In this article, the authors investigated the nonlinear bubble-plate interaction via boundary integral (BI) simulations with a particular focus on the effect of fluid-structure interaction (FSI) with a series of experiments of electric discharge cavitation bubbles.
TL;DR: In this article, the authors used the finite volume and volume of fluid methods to establish a compressible, three-dimensional air-gun bubble model in OpenFOAM (Open Field Operation and Manipulation).
TL;DR: In this article, the penalty immersed boundary method is adopted to couple the fluid and the submerged solid body, which is improved by considering both the normal and tangential relative velocities of the solid surface with an upwind scheme when updating the penetrated depth.
TL;DR: In this article, the dynamics of spark-generated cavitation bubbles near a deformable rubber sheet are investigated and the dependence of bubble behaviors and rubber response on two governing parameters (the bubble-rubber stand-off distance and the rubber thickness T) are systematically studied.
Abstract: Dynamics of spark-generated cavitation bubbles near a deformable rubber sheet are experimentally investigated in this study. The transient bubble–rubber interaction is captured by high-speed photography, including the expansion and collapse of the bubble, jetting behaviors, large deformation, and rupture of the rubber sheet. The dependence of bubble behaviors and rubber response on two governing parameters (the bubble–rubber stand-off distance $$\gamma $$
and the rubber thickness T) are systematically studied. Firstly, the bubble collapse patterns or jetting directions are categorized into three regimes. If the bubble is initially located at a large $$\gamma $$
from the rubber sheet, the jet is directed towards the boundary (regime I). Unexpectedly, when the generated bubble is close to the rubber sheet, it develops a jet away from the boundary (regime III). Bubble splitting and the formation of two axial liquid jets directing in opposite directions can only be observed with an intermediate $$\gamma $$
(regime II). A phase diagram of the bubble behaviors is given in the $$\gamma $$
–T space. For a large rubber sheet thickness (e.g., $$T=5$$
mm), only a downward jet is observed. From the perspective of jet direction, the effect of such a thick rubber sheet on the bubble dynamics is similar to that of a rigid wall. Note that the jet velocity and jet width may be slightly different. Secondly, the results reveal that bubble expansion can cause the boundary to deform. The strong axial jet towards the rubber sheet can damage and even rupture the rubber boundary. A parameter range within which the bubble jetting can rupture the rubber boundary is obtained. Besides, for a thin rubber sheet (
$$T \le 4$$
mm), the rupture is more likely to occur in regime II. For a thick rubber sheet (e.g., $$T=5$$
mm), the rupture can be seen when the jet directly impacts the rubber sheet (regime I).