Turbulent pipe flow is still an essentially open area of research, boosted in the last two decades by considerable progress achieved both on experimental and numerical frontiers, mainly related to identification characterization coherent structures as basic building blocks turbulence. It has been a challenging task, however, detect visualize these states. We address, means stereoscopic particle...

Abstract

A technique for adiabatic control of the population flow through a preselected decaying excited level in a three-level quantum ladder is presented. The population flow through the intermediate or upper level is controlled efficiently and robustly by varying the pulse delay between a pair of partly overlapping coherent laser pulses. The technique is analyzed theoretically and demonstrated in an ...

Development of coherent structures in the separated shear layer and wake of an airfoil in low-Reynolds-number flows was studied experimentally for a range of airfoil chord Reynolds numbers, 55×10 Rec 210×10, and three angles of attack, α=0◦, 5◦ and 10◦. To illustrate the effect of separated shear layer development on the characteristics of coherent structures, experiments were conducted for two...

We present an optical, noninvasive and label-free approach to characterize flow profiles in microfluidic devices. Coherent anti-Stokes Raman scattering signals were used to map the mass transport in a microfluidic device that was then related back to the local flow rate of dilute solutes having constant fluid properties. Flow characterization was demonstrated in two common types of microfluidic...

Understanding the long-time evolution of fluid motions is facilitated by studying the coherent structures of the flow. From an experimental perspective this has long been recognized since visualizations of complicated flows often exhibit very obvious structures. Some of the most commonly observed structures are vortices. These vortices may appear initially through some instability in an underly...

Streamline visualization can be formulated as the problem of streamline placement or streamline selection. In this paper, we present an importance-driven approach to view-dependent streamline selection that guarantees coherent streamline update when the view changes gradually. Given a large number of randomly or uniformly seeded and traced streamlines and sample viewpoints, our approach evaluat...

A study is made of some numerical calculations of two-dimensional and geostrophic turbulent flows. The primary result is that, under a broad range of circumstances, the flow structure has its vorticity concentrated in a small fraction of the spatial domain, and these concentrations typically have lifetimes long compared with the characteristic time for nonlinear interactions in turbulent flow (...