Effects of Particle Size on Dilute Particle Dispersion in a Karman Vortex Street Flow

It is shown that in a Karman vortex street flow, particle size influences the dilute particle dispersion. Together with an increase of the particle size, there is an emergence of a period-doubling bifurcation to a chaotic orbit, as well as a decrease of the corresponding basins of attraction. A crisis leads the attractor to escape from the central region of flow. In the motion of dilute particles, a drag term and gravity term dominate and result in a bifurcation phenomenon.

Attractor crisis and bursting in a fluid flow with two no-slip directions

Characteristic burtsing behavior is observed in a driven, two-dimensional viscous flow, confined to a square domain and subject to no-slip boundaries. Passing a critical parameter value, an existing chaotic attractor undergoes a crisis, after which the flow initially enters a transient bursting regime. Bursting is caused by ejections from and return to a limited subdomain of the phase space, whereas the precrisis chaotic set forms the asymptotic attractor of the flow. For increasing values of the control parameter the length of the bursting regime increases progressively. Passing another critical parameter value, a second crisis leads to the appearance of a secondary type of bursting, of very large dynamical range. Within the bursting regime the flow then switches in irregular intervals from the primary to the secondary type of bursting. Peak enstrophy levels for both types of bursting are associated to the collapse of a primary vortex into a quadrupolar state.

“微/纳系统国际会议(ICMNS 2002)”简介

<正>由中国力学学会、中科院力学所非线性力学国家重点实验室（LNM）、香港中文大学和香港科技大学联合主办的“微/纳系统国际会议（ICMNS 2002）”于 2002年8月11～14日在云南昆明万怡酒店隆重举行. 该会议国际学术委员会主席为中科院力学所郑哲敏院士,联合主席为中科院力学所白以龙院士、美国UCLA何志明教授和中科院副院长江绵恒研究员;国际程序委员会主席由中科院副院长白春礼院士担任;中科院力学所赵亚溥研究员和香港中文大学的李文荣分别担任大会组织委员会主席和联合主席.出席会议的正式代表为150人,其中来自北美、欧洲、亚洲以及港台地区的境外代表为47人.正如何志明教授所

中国科学院力学研究所2002年度科研进展

<正> 2002年是力学所整体进入院知识创新工程试点的第二年,对力学所科研人员而言,这是十分充实的一年.力学所在中科院新时期办院方针的指引下,锐意进取,在诸多方面取得了重要的进展.

2002年度非线性力学国家重点实验室学术年会简介

<正> 2002年度非线性力学国家重点实验室(LNM)第14届学术年会于2002年12月21—22日在中国科学院力学研究所隆重举行.本次年会受到了所内外学术同行的广泛关注和重视,有10余个单位的近200人参加了本次LNM学术年会.

Characterization of airborne carbonate over a site near Asian dust source regions during spring 2002 and its climatic and environmental significance

IEECAS SKLLQG

A Global Crisis for Seagrass Ecosystems

Seagrasses, marine flowering plants, have a long evolutionary history but are now challenged with rapid environmental changes as a result of coastal human population pressures. Seagrasses provide key ecological services, including organic carbon production and export, nutrient cycling, sediment stabilization, enhanced biodiversity, and trophic transfers to adjacent habitats in tropical and temperate regions. They also serve as “coastal canaries,” global biological sentinels of increasing anthropogenic influences in coastal ecosystems, with large-scale losses reported worldwide. Multiple stressors, including sediment and nutrient runoff, physical disturbance, invasive species, disease, commercial fishing practices, aquaculture, overgrazing, algal blooms, and global warming, cause seagrass declines at scales of square meters to hundreds of square kilometers. Reported seagrass losses have led to increased awareness of the need for seagrass protection, monitoring, management, and restoration. However, seagrass science, which has rapidly grown, is disconnected from public awareness of seagrasses, which has lagged behind awareness of other coastal ecosystems. There is a critical need for a targeted global conservation effort that includes a reduction of watershed nutrient and sediment inputs to seagrass habitats and a targeted educational program informing regulators and the public of the value of seagrass meadows.