In this chapter, we present and discuss time-averaged turbulence parameters based on time and Fourier-domain analyses. In particular, we stress how the different configurations influence such parameters. All data analyzed in this chapter are obtained from velocity records sampled at a frequency of 4000Hz over a period of 180 seconds. The velocity measurements were taken at the height of 7.92cm,...

A hot-air turbulence emulator is employed for generating controlled optical clear air turbulence in the weak fluctuation regime in laboratory conditions. The analysis of the first and second-order statistical moments of the fluctuating intensity of a propagating infra-red (IR) laser beam through the turbulence emulator is made and the results are compared with bi-directional shore-to-ship marit...

To elucidate the influence of shear flow on the generation of magnetic field (the dynamo effect), we study the kinematic limit where the magnetic field does not backreact on the velocity field. By non-perturbatively incorporating the effect of shear in a helically forced turbulence, we show that turbulence intensity and turbulent transport coefficients (turbulent viscosity, α and β effect) are ...

We compute the structure function scaling of the integrated intensity images of two J=1-0 CO maps of Taurus and Perseus. The scaling exponents of the structure functions follow the velocity scaling of super–sonic turbulence, suggesting that turbulence plays an important role in the fragmentation of cold interstellar clouds. The data also allows to verify the validity of the two basic assumption...

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...

In free-space optical communication links using intensity modulation and direct detection (IM/DD), atmospheric turbulence-induced intensity fluctuations can significantly impair link performance. Communication techniques can be applied to mitigate turbulence-induced intensity fluctuations (i.e., signal fading) in the regime in which the receiver aperture 0 is smaller than the fading correlation...

Turbulence is a major aviation hazard for both commercial and private aircraft. Currently, the clear-air turbulence forecasting tool Graphical Turbulence Guidance (GTG) is used by airline meteorologists and dispatchers for flight planning, and in part to determine operational Airman’s Meteorological Information (AIRMET) turbulence advisories; however, GTG has much higher resolution and intensit...

We investigated the scintillation properties of nonuniformly correlated (NUC) beams in atmospheric turbulence and have shown that NUC beams can not only have lower scintillation but also higher intensity than Gaussian-Schell model beams and even higher intensity than coherent Gaussian beams over certain propagation distances.

in this study, the characteristics of the wake around a rotating circular cylinder have been investigated experimentally. to this end, a cylinder with a circular cross-section of plexiglas with the length of 400 mm and a diameter of 20 mm have been tested in the wind tunnel. using existing methods, the characteristics of the wake and the drag coefficients of the model in different cases have be...

The bit error rate (BER) expression and performance of free-space optical communication link in clear but turbulent atmosphere using subcarrier intensity modulation (SIM) with differential phase shift keying (DPSK) is presented. The practical linear combining technique suitable for differentially modulated data (selection combining) is considered and its performance evaluated under weak atmosph...