Draft is one of the most common complaints in the indoor environment. It may be caused by convective air currents along windows and other cold surfaces providing air movement in the occupied zone of heated spaces. The present paper comprises measurements of airflow characteristics (mean velocity, turbulence intenSity, energy spectra of the velocity fluctuations, etc.) in a wide range of spaces ...

We show quantitatively how the collision rate of droplets of visible moisture in turbulent air increases very abruptly as the intensity of the turbulence passes a threshold, due to the formation of fold caustics in their velocity field. The formation of caustics is an activated process, in which a measure of the intensity of the turbulence, termed the Stokes number St, is analogous to temperatu...

This work is motivated by the need to understand the ultimate capacity of the outdoor long-distance optical wireless communication with intensity modulation and direct detection. The channel under weak atmospheric turbulence is modeled as a stationary ergodic channel with lognormal intensity fading, where signals experience asymmetric statistics due to on-off keying signaling. Ergodic channel c...

We present estimates of the angular power spectra of the synchrotron radiation intensity fluctuations at 6 and 20 cm for the shell type supernova remnant Cas A and the filled-centre Crab supernova remnant. We find that the intensity fluctuations of both sources have a power law power spectrum with index −3.24 ± 0.03. This power law power spectrum is consistent with the magnetohydrodynamic turbu...

In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of received light signal, impairing link performance. In this paper, we describe several communication techniques to mitigate turbulence-induced intensity fluctuations, that is signal fading. These techniques are applicable in the regime in which the receiver aperture is sma...

High-resolution numerical simulations of a tethered model bumblebee in forward flight are performed superimposing homogeneous isotropic turbulent fluctuations to the uniform inflow. Despite tremendous variation in turbulence intensity, between 17% and 99% with respect to the mean flow, we do not find significant changes in cycle-averaged aerodynamic forces, moments, or flight power when average...

Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a fixed elevation angle and the resulting measurements are used to derive an estimate of the nminute horizontal mean wind velocity (speed and direction). Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind fluctuation...

In this paper the impact of atmospheric turbulence on helicopter handling qualities is investigated using a simple random turbulence representation and a structural human pilot model. Linear approximation of the turbulence field and the frozen field concept are assumed. Effects of uniform field component and spatial gradients in the horizontal plane are individually evaluated on each axis. Turb...

Turbulence is a challenging feature common to a wide range of complex phenomena. Random fibre lasers are a special class of lasers in which the feedback arises from multiple scattering in a one-dimensional disordered cavity-less medium. Here we report on statistical signatures of turbulence in the distribution of intensity fluctuations in a continuous-wave-pumped erbium-based random fibre laser...