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CFD Simulation of flow features and Vorticity Structures in Tuna-Like Swimming

China Ocean Engineering 2011年第1期25卷 73-82页

作者：杨亮苏玉民 State Key Laboratory of Autonomous Underwater Vehicle Harbin Engineering University

The theoretical research on the propulsive principle of aquatic animal becomes more important and attracted more researchers to make efforts on it. In the present study, a computational fluid dynamic （CFD） simulation of a three-dimensional traveling-wave undulations body of tuna has been developed to investigate the fluid flow features and vorticity structures around this body when moving in a straight line. The undulation only takes place in the posterior half of the fish, and the tuna-tail is considered as a lunate fin oscillating with the mode combined swaying with yawing. A Reynolds-averaged Navier-Stokes （RANS） equation is developed, employing a control-volume method and a k-omega SST turbulent model; meanwhile an unstructured tetrahedral grid, which is generated for the three-dimensional geometry, is used based on the deformation of the hind parts of the body and corresponding movement of the tail. We calculated the hydrodynamic performance of tuna-like body when a tuna swims in a uniform velocity, and compared the input power coefficient, output power coefficient and propulsive efficiency of the oscillating tuna-tail with or without body vortex shedding. Additionally, the load distribution on the body, flow features and vorticity structures around the body were demonstrated. The effect of interaction between the body-generated vortices and the tail-generated vorticity on the hydrodynamic performance can be obtained.

关键词： CFD flow features vorticity structures hydrodynamic performance

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CATH: an effective method for detecting denial-of-service attacks in software defined networks

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Science China(Information Sciences) 2019年第3期62卷 75-89页

作者： Yi GUO Fu MIAO Liancheng ZHANG Yu WANG State Key Laboratory of Mathematical Engineering and Advanced Computing Institute for Network Science and Cyberspace Tsinghua University School of Computer Science Henan University of Engineering

Software defined networks(SDNs) are innovative network frameworks that have recently received wide attention. Their programming flexibility facilitates automatic network management and control, thus mitigating existing issues in the traditional network architecture. However, SDNs face several security risks,in particular denial-of-service(DoS) attacks, the most common and serious network attacks. To address such a threat, an SDN-DoS attack detection method is proposed based on fusing multiple flow features for describing the network catastrophe between the normal and the attack state. Several statistic attributes of SDN flow information are first chosen as detection features; subsequently, the cusp model is used to establish a catastrophe equilibrium surface for SDN states. After being trained, the cusp catastrophe model can be utilized to infer whether an SDN is under DoS attack. The experimental results demonstrate that the method can effectively and timely perceive SDN-DoS attacks, not only in simple networks but also in larger enterprise networks.

关键词： DoS attacks software defined network flow features cusp model equilibrium surface

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Hepatocyte culture in a radial-flow bioreactor with plasma polypyrrole coated scaffolds

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BIOCELL 2015年第2期39卷 9-14页

作者： Odin RAMÍREZ-FERNÁNDEZ Rafael GODÍNEZ Esmeralda ZUÑIGA-AGUILAR Luis E.GÓMEZ-QUIROZ María C.GUTIÉRREZ-RUIZ Juan MORALES Roberto OLAYO Departamento de Ingeniería Eléctrica Universidad Autónoma MetropolitanaUnidad IztapalapaApdo.Postal 55-534IztapalapaMéxico. Departamento de Ciencias de la Salud Universidad Autónoma MetropolitanaUnidad IztapalapaApdo.Postal 55-534IztapalapaMéxico Departamento de Física Universidad Autónoma MetropolitanaUnidad IztapalapaApdo.Postal 55-534IztapalapaMéxico

We have designed and evaluated a radial-flow bioreactor for three-dimensional liver carcinoma cell culture on a new porous coated *** designed a culture chamber where a radial flow of culture medi-um was continuously delivered through *** this system was established,flow was simulated using flow dy-namics software based on numeric methods to solve Navier-Stockes flow *** within cell culture scaffolds was simulated using a flow velocity of 7 mL/min and found that cell culture medium was distributed unhindered in the bioreactor ***,the bioreactor was built according to the simulated design and was tested with liver carcinoma cells(HepG2)cultured over an L-polylactic acid scaffold whose surface was modified with iodine-doped *** bioreactor was tested under non-flow and in radial flow *** density under radial flow conditions was almost double than that under static conditions and both total protein and albumin output was also increased under radial flow conditions.

关键词： Cell Cultures flow Simulation flow features HepG2 Cells Plasma Polymerization

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