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...

1 The propagation of a laser beam through turbulent media is modeled as a fractional Brownian motion (fBm). Time series corresponding to the center position of the laser spot (coordinates x and y) after traveling across air in turbulent motion, with different strength, are analyzed by the wavelet theory. Two quantifiers are calculated, the Hurst exponent and the Normalized Total Wavelet Entropy...

The implications of twist in active region magnetic elds is considered in this paper. The latitudinal distribution of twist that has been derived from recent vector magnetogram observations may be explained by the eeects of convective turbulence with a non-zero kinetic helicity acting on active region scale magnetic ux tubes as they rise through the convection zone. Highly twisted, kink unstabl...

Measurements of partially spatially coherent infra-red laser beam intensity fluctuations propagating through a hot-air turbulence emulator are compared with visible laser beam intensity fluctuations in the maritime and IR laser beam intensity fluctuations in the terrestrial environment at the United States Naval Academy. The emulator used in the laboratory for the comparison is capable of gener...

Abstract Aiming at the low sensitivity of weak turbulent wake detection underwater vehicles, studied laser propagation characteristics in turbulence, and then proposed a method based on statistical scintillation peak Gaussian vortex beam for detecting turbulence fluctuation. According to refractive index power spectrum flume, intensity distribution images propagating through flume are simulated...

An aperture composed of multiple small apertures has several advantages over a large continuous aperture when practical issues are included in the analysis. For example, a single bullet can easily produce a catastrophic failure of the laser communication link if all the optical gain for the transmitter (or receiver) is derived from a single large-diameter telescope. In addition to battlefield c...

in this paper, inflow turbulence effects on the flow wake parameters around a naca0012 airfoil at zero incidence angle and reynolds number of 38,700 were investigated. various turbulence promoter networks were used to achieve turbulence intensity of 5% and 6%. experiments have been conducted for three different turbulence intensities in which mean velocity parameters, turbulence intensity, freq...

The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited...

We define turbulent-turbulent spot as a local concentration of vortices with high level of swirling strength originating from hairpin packet in a turbulent boundary layer. We also define bypass transition in the narrow sense as the breakdown of the Blasius boundary layer beneath freestream homogeneous isotropic turbulence with an initial amplitude of 1 to 4 percent. We present evidence for the ...

1 The propagation of a laser beam through turbulent media is modeled as a fractional Brownian motion (fBm). Time series corresponding to the center position of the laser spot (coordinates x and y) after traveling across air in turbulent motion, with different strength, are analyzed by the wavelet theory. Two quantifiers are calculated, the Hurst exponent, H, and the mean Normalized Total Wavele...