流体力学杂志“Journal of Fluid Mechanics”由剑桥大学教授George Batchelor在1956年5月创办，在国际流体力学界享有很高的学术声望，被公认为是流体力学最著名的学术刊物之一，2005年的影响因子为2．061，雄居同类期刊之首．在它创刊50周年之际，2006年5月JFM出版了第554卷的纪念特刊，其中刊登了现任主编（美国西北大学S．H．Davis教授和英国剑桥大学T．J．Pedley教授）合写的述评：“Editorial：JFM at50”，以JFM为背景，从独特的视角对近50年来流体力学的发展进行了简明的回顾和展望，并归纳了一系列非常有启发性的有趣统计数字．2006年7月21日在剑桥大学应用数学和理论物理研究所（DAMTP）举行了创刊50周年的庆祝会．下午2点，JFM的新老编辑和来宾会聚一堂，Pedley教授致开幕词，其后是5个精彩的报告：The mysterious rattleback and its fluid counterpart（Keith Moffatt），Developments in shear instabilities（Patrick Huerre），Falling clouds（Elisabeth Guazzelli），Ecotectural fluid mechanics（Paul Linden），The success of JFM（Herbert Huppert），最后由Davis教授致闭幕词．

Journal of Fluid Mechanics创刊50周年

Effects of large computational time steps on the computed turbulence were investigated using a fully implicit method. In turbulent channel flow computations the largest computational time step in wall units which led to accurate prediction of turbulence statistics was determined. Turbulence fluctuations could not be sustained if the computational time step was near or larger than the Kolmogorov time scale.

Effects of the computational time step on numerical solutions for turbulent flow

Lagrangian coherent structures

Influence of OPC replacement and manufacturing procedures on the properties of self-cured geopolymer

A concise and factual abstract is required. The abstract should state briefly the purpose of the research, the principal results and major conclusions. An abstract is often presented separately from the article, so it must be able to stand alone. For this reason, References should be avoided, but if essential, then cite the author(s) and year(s). Also, non-standard or uncommon abbreviations should be avoided, but if essential they must be defined at their first mention in the abstract itself.

Progress in aerospace sciences

The present study investigates the complex vortex interactions in two-dimensional flow-field behind a symmetric NACA0012 airfoil undergoing a prescribed periodic pitching-plunging motion in low Reynolds number regime. The flow-field transitions from periodic to chaotic through a quasi-periodic route as the plunge amplitude is gradually increased. This study unravels the role of the complex interactions that take place among the main vortex structures in making the unsteady flow-field transition from periodicity to chaos. The leading-edge separation plays a key role in providing the very first trigger for aperiodicity. Subsequent mechanisms like shredding, merging, splitting, and collision of vortices in the near-field that propagate and sustain the disturbance have also been followed and presented. These fundamental mechanisms are seen to give rise to spontaneous and irregular formation of new vortex couples at arbitrary locations, which are the primary agencies for sustaining chaos in the flow-field. The...

Investigating chaotic wake dynamics past a flapping airfoil and the role of vortex interactions behind the chaotic transition

This study investigates energy harvesting from vortex induced vibrations of a flexible cantilevered flapper placed in the wake of a rigid circular cylinder. The effect of the gap between the cylinder and the flapper on the energy harvested is investigated through wind tunnel experiments and numerical simulations. As the flow speed is varied, a transition in the flapper dynamics is observed, which in turn affects the power extracted by the harvester. Numerical investigations reveal that the flapper dynamics is different depending on whether the vortices are shed ahead or behind the flapper. This study concludes that the choice of the gap influences the energy harvesting potential of such harvesters.

Investigations on a vortex induced vibration based energy harvester

Chaotic wake patterns in the flow past flapping airfoils have been reported earlier for high plunge velocities. The present work focuses on analysing the dynamics and identifying the route to chaos in this phenomenon. The unsteady flow-field is investigated using an incompressible Navier–Stokes solver. A bifurcation analysis with the plunge amplitude as the control parameter reveals that, for high plunge amplitudes, periodic vortex patterns in the wake are interrupted by abrupt chaotic patterns. The frequency of occurrence of these chaotic patterns increases on further increasing the bifurcation parameter and eventually the flow-field becomes completely chaotic. This behaviour is typically observed in systems exhibiting intermittency route to chaos, and to the best of our knowledge this has not been reported for flows past flapping airfoils. The intermittency route to chaos is conclusively established using techniques from time series analysis, such as, phase space reconstruction and recurrence plots. A qualitative analysis of the patterns in the recurrence plots is used to identify the type of intermittency to be Type I. Moreover, the implication of Type I intermittency into the flow dynamics has been studied through various vortex interaction mechanisms and its effect on the thrust generation. Quantitative measures obtained from the recurrence plots provide more insights into the dynamics as well as an early indication for the onset of chaos.

Chandan Bose

Papers

Investigating chaotic wake dynamics past a flapping airfoil and the role of vortex interactions behind the chaotic transition

Investigations on a vortex induced vibration based energy harvester

Identifying the route to chaos in the flow past a flapping airfoil

Capturing the dynamical transitions in the flow-field of a flapping foil using Immersed Boundary Method

Dynamical Stability Analysis of a Fluid Structure Interaction System Using a High Fidelity Navier-stokes Solver