Flow visualization using fluorescence from locally seeded I2 excited by an ArF excimer laser

 A new concept for flow visualization is demonstrated in which fluorescence from locally seeded iodine is viewed in the wake of simple aerodynamic models at Mach 6. Localized seeding is performed by painting a small area of a ceramic model with a tincture of iodine. When the model is injected into the flow, the adsorbed iodine is entrained into the boundary layer, follows the model contour, and ultimately mixes into the wake region. Planar “snapshots” of the wake flow are taken by exciting the iodine with an ArF excimer laser sheet at 193 nm and observing the fluorescence in the 210–600 nm region with an intensified CCD camera. Received: 17 July 1997/Accepted: 12 August 1998     

Velocity domain and volume fraction distribution of heavy microparticles in low reynolds number flow in microchannel

In this paper, a two-dimensional Stokes flow having particle size distribution ranging from 10 to 50 µm in a rectangular channel is simulated numerically with focus on the hydrodynamic forces. The results show that due to the disparity between the density of the fluid and particles, velocity domain of particles deviates from the fluid velocity domain and this phenomenon occurs significantly for the larger particles. Also, with the increase of Reynolds number, the volume fraction of dispersed phase near the bottom wall of the channel increases either. Compared to similar studies, this investigation employs numerical simulation of microparticulate flow and interparticle hydrodynamic forces with emphasis on the dispersed phase volume fraction in order to present the microchannel flow properties.     

Nonlinear continuous integral-derivative observer

In this paper, a high-order nonlinear continuous integral-derivative observer is presented based on finite-time stability and singular perturbation technique. Not only the proposed integral-derivative observer can obtain the multiple integrals of a signal, but also the derivatives can be estimated. Conditions are given ensuring finite-time stability for the presented integral-derivative observer, and the stability and robustness in time domain are analyzed. The merits of the presented integral-derivative observer include its synchronous estimation of integrals and derivatives, finite-time stability, ease of parameters selection, sufficient stochastic noises rejection and almost no drift phenomenon. The theoretical results are confirmed by computational analysis and simulations.