2019-01

Smoothed particle hydrodynamics (SPH) for complex fluid flows: Recent developments in methodology and applications

Ting Ye, Dingyi Pan, Can Huang, and Moubin Liu

Abstract:

Computer modeling of complex fluid flows usually presents great challenges for conventional grid-based numerical methods. Smoothed particle hydrodynamics (SPH) is a meshfree Lagrangian particle method and has special advantages in modeling complex fluid flows, especially those with large fluid deformations, fluid-structure interactions, and multi-scale physics. In this paper, we review the recent developments of SPH in methodology and applications for modeling complex fluid flows. Specifically, in methodology, some important issues including modified SPH particle approximation schemes for improving discretization accuracy, different particle regularization techniques, and various boundary treatment algorithms for solid boundary, free surface, or multiphase interface are described. More importantly, the SPH method with ideas from the dissipative particle dynamics for complex fluids in macro-or meso-scales is discussed. In applications, different complex fluid flows, including biological flows, microfluidics and droplet dynamics, non-Newtonian fluid flows, free surface flows, multiphase flows, and flows with fluid-structure interaction, are reviewed. Some concluding remarks in SPH modeling of complex fluid flows are provided.

Reference:

T. Ye, D.Y. Pan, C. Huang, M.B. Liu, Smoothed particle hydrodynamics (SPH) for complex fluid flows: Recent developments in methodology and applications, Physics of Fluids, 2019, 31: 011301.

2019-01

事件驱动的强化学习多智能体编队控制

徐鹏 谢广明 文家燕 高远

Abstract:

针对经典强化学习的多智能体编队存在通信和计算资源消耗大的问题,本文引入事件驱动控制机制,智能体的动作决策无须按固定周期进行,而依赖于事件驱动条件更新智能体动作。在设计事件驱动条件时,不仅考虑智能体的累积奖赏值,还引入智能体与邻居奖赏值的偏差,智能体间通过交互来寻求最优联合策略实现编队。数值仿真结果表明,基于事件驱动的强化学习多智能体编队控制算法,在保证系统性能的情况下,能有效降低多智能体的动作决策频率和资源消耗。

2019-01-15

High-accuracy transient response fiber optic seismic accelerometer using a shock-absorbing ring as a mechanical antiresonator

Yi, Duo; Liu, Fei; Zhang, Min; Tao, Qingchang

Abstract:

This study proposes a high-accuracy transient response fiber optic seismic accelerometer based on the resonance suppression mechanism. A shock-absorbing ring is embedded in the accelerometer structure, which acts as a mechanical antiresonator. The experimental results show that the sensitivity at the resonance frequency is suppressed by 21.79 dB, and the 3 dB operating bandwidth is extended without reducing the average sensitivity. Under this condition, the high-accuracy transient response is obtained during the vibration-event test. This study provides a practical seismic acquisition technique solution for vertical seismic profiling monitoring in the smart oilfield. (C) 2019 Optical Society of America

Reference:

Duo, Yi, et al. "High-accuracy transient response fiber optic seismic accelerometer using a shock-absorbing ring as a mechanical antiresonator."Optics letters 44.2 (2019): 183-186.