To simulate the effect of free st ream turbulence on turbulent spot formation, experiments were conducted on the interaction of localized three-dimensional disturbances with the harmonic waves in a laminar boundary layer on a flat plate. Experiments conducted in three-dimensional diverging flow (but zero pressure gradient) show, while individually the disturbances decay downstream, their intera...

In this paper propagation of combined laser beam through atmosphere is investigated. Laser beam is combined via lens array arrangement. Turbulence is considered as an affecting factor of atmosphere and its effects on transverse coherence length (Fried parameter), peak intensity, propagation efficiency, and spot size of the laser beam is investigated. Coherent and incoherent combined beam are co...

The design and implementation of an interactive spot noise algorithm is presented. Spot noise is a technique which utilizes texture for the visualization of flow fields. Various design tradeoffs are discussed that allow an optimal implementation on a range of high end graphical workstations. Two applications are given: the steering of a smog prediction simulation and browsing a very large data ...

We use a quasi-geostrophic numerical model to study the turbulence of rotating flows in a sphere, with realistic Ekman friction and bulk viscous dissipation. The forcing is caused by the destabilization of an axisymmetric Stewartson shear layer, generated by differential rotation, resulting in a forcing at rather large scales. The equilibrium regime is strongly anisotropic and inhomogeneous but...

Adaptive optics takes its servo feedback error cue from a wavefront sensor. The common Hartmann-Shack spot grid that represents the wavefront slopes is usually analyzed by finding the spot centroids. In a novel application, we used the Fourier decomposition of a spot pattern to find deviations from grid regularity. This decomposition was performed either in the Fourier domain or in the image do...

In developed turbulence, the effective magnetic pressure of a large-scale field (non-turbulent plus turbulent contributions) can become negative. This is known to lead to a large-scale instability in strongly stratified turbulence that produces spontaneous magnetic flux concentrations. Previous studies using a horizontal magnetic field resulted in elongated field concentrations with a strength ...

We analyze, within the wavelet theory framework, the wandering over a screen of the centroid of a laser beam after it has propagated through a time-changing laboratory-generated turbulence. Following a previous work (Fractals 12 (2004) 223) two quantifiers are used, the Hurst parameter,H, and the Normalized Total Wavelet Entropy, NTWS. The temporal evolution of both quantifiers, obtained from t...

Brown dwarfs and giant gas planets are substellar objects whose spectral appearance is determined by the chemical composition of the gas and the solids/liquids in the atmosphere. Atmospheres of substellar objects possess two major scale regimes: large-scale convective motions + gravitational settling and small-scale turbulence + dust formation. Turbulence initiates dust formation spot-like on s...

Since financial derivatives are key instruments for risk taking as well as risk reduction, it is only straightforward to examine their role in currency crises. This paper addresses this issue by investigating the impact of currency futures trading on the underlying exchange rates. After a discussion of trading mechanisms and trader types, the linkage between futures trading activity and spot ma...

Numerical simulations of a model of plane Couette flow focusing on its in-plane spatio-temporal properties are used to study the dynamics of turbulent spots. While the core of a spot is filled with small scale velocity fluctuations, a large scale flow extending far away and occupying the full gap between the driving plates is revealed upon filtering out small scales. It is characterized by stre...