A recent study [D. Helbing, A. Johansson, and H. Z. Al-Abideen, Phys. Rev. E 75, 046109 (2007)] has revealed a "turbulent" state of pedestrian flows, which is characterized by sudden displacements and causes the falling and trampling of people. However, turbulent crowd motion is not reproduced well by current many-particle models due to their insufficient representation of the local interaction...

Owing to complex geometry, gyrokinetic simulations in stellarator geometry produce large numbers of subdominant unstable and stable, near-orthogonal eigenmodes. Here, results based on the full eigenmode spectrum in stellarator geometry are presented for the first time. In the nonlinear state of a low-magnetic-shear ion-temperature-gradient-driven case, a multitude of these modes are active and ...

Free space optical (FSO) communication in a maritime environment involves unique challenges due to the existing environmental conditions. An important degradation factor is atmospheric turbulence that causes irradiance fluctuations (scintillation) at detector. A significant amount of theoretical and experimental research has been conducted quantify those effects. This paper presents results an ...

Stochastic flows mimicking 2D turbulence in compressible media are considered. Particles driven by such can collide and we study the collision (caustic) frequency. Caustics occur when Jacobian of a flow vanishes. First, system nonlinear stochastic differential equations involving is derived reduced to smaller number unknowns. Then, for special cases forcing, upper lower bounds found mean causti...

In this study we highlight the influence of mean dilatation and mean density gradient on the Reynolds stress modeling of compressible, heat-releasing and supercritical turbulent flows. Firstly, the modeling of the rapid pressure-strain correlation has been extended to self-consistently account for the influence of mean dilatation. Secondly, an algebraic model for the turbulent density flux has ...

Understanding turbulent flows is a "grand challenge" comparable to other prominent scientific problems such as the large-scale structure of the universe and the nature of subatomic particles. In contrast to many of the other grand challenges, progress on the basic theory of turbulence translates nearly immediately into a wide range of engineering applications and technological advances that aff...