[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This paper assesses some recent trends in the novel numerical meshless method smoothed particle hydrodynamics, with particular focus on its potential use in modelling free-surface flows. Due to its Lagrangian nature, smoothed particle hydrodynamics (SPH) appears to be effective in solving diverse fluid-dynamic problems with highly nonlinear deformation such as wave breaking and impact, multi-phase mixing processes, jet impact, sloshing, flooding and tsunami inundation, and fluid–structure interactions. The paper considers the key areas of rapid progress and development, including the numerical formulations, SPH operators, remedies to problems within the classical formulations, novel methodologies to improve the stability and robustness of the method, boundary conditions, multi-fluid approaches, particle adaptivity, and hardware acceleration. The key ongoing challenges in SPH that must be addressed by academic research and industrial users are identified and discussed. Finally, a roadmap is propose...

Smoothed particle hydrodynamics (SPH) for free-surface flows: past, present and future

Smoothed particle hydrodynamics method for fluid flows, towards industrial applications: Motivations, current state, and challenges

Comparative study on accuracy and conservation properties of two particle regularization schemes and proposal of an optimized particle shifting scheme in ISPH context

The article aims at providing an up-to-date review on several latest advancements related to particle methods with applications in coastal and ocean engineering. The latest advancements corresponding to accuracy, stability, conservation properties, multiphase multi-physics multi-scale simulations, fluid-structure interactions, exclusive coastal/ocean engineering applications and computational efficiency are reviewed. The future perspectives for further enhancement of applicability and reliability of particle methods for coastal/ocean engineering applications are also highlighted.

/pdf/on-the-state-of-the-art-of-particle-methods-for-coastal-and-4emfnigqnn.pdf

On the state-of-the-art of particle methods for coastal and ocean engineering

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.

Interaction of two out-of-phase underwater explosion bubbles

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.

A-Man Zhang

Papers

Interaction of two out-of-phase underwater explosion bubbles

On differences and comparisons of peridynamic differential operators and nonlocal differential operators

Continuous simulation of the whole process of underwater explosion based on Eulerian finite element approach

A hydroelastic fluid–structure interaction solver based on the Riemann-SPH method

A 3D meshfree crack propagation algorithm for the dynamic fracture in arbitrary curved shell