Search results for " turbulence"

Mixing processes in vegetated rivers: experimental investigation in a laboratory flume

2018

The presence of vegetation in rivers exerts an important ecological function and is very important to maintain suitable habitat. Especially in recent years, some researchers (among others Perrucca et al., 2007) have focused their attention on the role of vegetation in channel’s morphodynamics. Alteration of hydrological conditions in fluvial systems inevitably leads to changes in river morphology, riparian or riverbed vegetation and ecosystems. Riparian vegetation distribution could also change in time and in space depending on the combination of factors affecting the settling and growth of vegetated elements. In the present paper attention is focused on the turbulent and mixing processes i…

Generalization of Vinen's equation including transition to superfluid turbulence

2005

The two-fluid extended model of superfluid helium

2019

In this paper we perform the first numerical comparison between the two main existing models of superfluid helium: the two-fluid model proposed by Landau and the one-fluid extended model proposed from the extended thermodynamics. The numerical experiments in this paper regard the profiles of the so-called normal and superfluid components in 2D counterflow turbulence.

Eperimental observations on the effect of flexible vegetation on flow velocity and turbulence fields

2011

Vegetation altering hydrodynamic conditions of an open channel flow controls the exchanges of sediment, nutrients and contaminants. Thus, the knowledge of the hydraulic characteristics of flow over vegetation is very important to support the management of fluvial processes. But, the analysis of the hydrodynamic conditions is complex because vegetation is flexible in varying degrees and it oscillates in the flow changing position. Furthermore, because of temporal changing of roughness due to natural vegetative growth, the response of vegetation to the flow can change in time. Many theoretical and experimental investigations have been performed in order to analyze both the mean flow and turbu…

Phenomenological description of the vortex density in rotating BEC superfluids

2008

The close analogy of a purely magnetic excitation scheme, used in the experiments on Bose-Einstein condensate by Hodby et al., and the rotating bucket experiments with liquid helium 4 has suggested us to apply a phenomenological equation for the vortex line density, previously proposed for rotating superfluid helium 4, to describe the vortex density in a rotating Bose-Einstein condensate as a function of the angular speed. In both systems, the phenomenological equation provides a reasonable description of the observed data.

MR2997965 (Review) 37D45 Viana, R. L.; Lopes, S. R.; Szezech, J.D., Jr.; Caldas, I. L. Synchronization of chaos and the transition to wave turbulence…

2013

In this paper the authors analyze the onset of the wave turbulence in the spatially extended threewave interacting model by using the concept of synchronization. In order to work with a set of ordinary differential equations, they make a pseudo-spectral decomposition of the wave field and identify the onset of wave turbulence as the excitation of spatial modes in the presence of underlying temporally chaotic dynamics. Each spatial point is regarded as a nonlinear oscillator and the onset of wave turbulence is the point where the oscillators lose phase synchronization. The authors use an extremely sensitive complex-order parameter to estimate the threshold of weak turbulence and perform a Ly…