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Where and under what conditions the transfer of energy between electromagnetic fields and particles takes place in the solar wind remains an open question. We investigate the conditions that promote the growth of kinetic instabilities…

A certain appeal to the alpha model for turbulence and related viscosity in accretion disks was that one scales the Reynolds stresses simply on the thermal pressure, assuming that turbulence driven by a certain mechanism will attain a…

Earth and Planetary Astrophysics · Physics 2021-09-22 Natascha Manger , Thomas Pfeil , Hubert Klahr

Mitigating climate change demands a transition towards renewable electricity generation, with wind power being a particularly promising technology. Long periods either of high or of low wind therefore essentially define the necessary amount…

Atmospheric and Oceanic Physics · Physics 2020-01-07 Juliane Weber , Mark Reyers , Christian Beck , Marc Timme , Joaquim G. Pinto , Dirk Witthaut , Benjamin Schäfer

A statistically stationary and nearly homogeneous turbulent shear flow is established by an additional volume forcing in combination with stress-free boundary conditions in the shear direction. Both turbulent energy and enstrophy are…

Chaotic Dynamics · Physics 2019-06-19 Joerg Schumacher

This work presents numerical results on the transport of heat and chemical species by shear-induced turbulence in strongly stratified but thermally diffusive environments. The shear instabilities driven in this regime are sometimes called…

Solar and Stellar Astrophysics · Physics 2016-04-20 Pascale Garaud , Logithan Kulenthirarajah

Using the Lagrangian transport of momentum, the Reynolds shear stress can be expressed in terms of basic turbulence parameters. In this view, the Reynolds stress gradient represents the lateral transport of streamwise momentum, balanced by…

Fluid Dynamics · Physics 2020-07-28 T. -W. Lee

We perform molecular dynamics simulations of model granular systems undergoing boundary-driven planar shear flow in two spatial dimensions with the goal of developing a more complete understanding of how dense particulate systems respond to…

Soft Condensed Matter · Physics 2009-11-11 Ning Xu , Corey S. O'Hern , Lou Kondic

Reliably predicting the geomorphology and climate of planetary bodies requires knowledge of the dynamic threshold wind shear velocity below which saltation transport ceases. Here we measure this threshold in a wind tunnel for four…

Geophysics · Physics 2019-10-28 Wei Zhu , Xinghui Huo , Jie Zhang , Peng Wang , Thomas Pähtz , Ning Huang , Zhiguo He

Kinetic-scale current sheets observed in the solar wind are frequently approximately force-free despite the fact that their plasma $\beta$ is of the order of one. In-situ measurements have recently shown that plasma density and temperature…

Space Physics · Physics 2020-03-18 T. Neukirch , I. Y. Vasko , A. V. Artemyev , O. Allanson

Although the notion of mechanical noise is expected to play a key role in the non-linear rheology of athermally sheared amorphous systems, its characterization has so far remained elusive. Here, we show using molecular dynamic simulations…

Soft Condensed Matter · Physics 2015-08-27 Francesco Puosi , Julien Olivier , Kirsten Martens

We analyze the linear stability of monoclinal traveling waves on a constant incline, which connect uniform flowing regions of differing depths. The classical shallow-water equations are employed, subject to a general resistive drag term.…

Fluid Dynamics · Physics 2022-05-18 Jake Langham , Andrew J. Hogg

The linear stability of a stratified shear flow for smooth density profiles is studied. This work focuses on the nature of the stability boundaries of flows in which both Kelvin-Helmholtz and Holmboe instabilities are present. For a fixed…

Fluid Dynamics · Physics 2009-11-11 Alexandros Alexakis

Data available in literature from direct numerical simulations of two-dimensional turbulent channels by Lee & Moser (2015), Bernardini et al. (2014), Yamamoto and Tsuji (2018) and Orlandi et al. (2015) in a large range of Reynolds number…

Fluid Dynamics · Physics 2019-01-08 Paolo Orlandi

We propose a procedure to estimate the fatigue loads on wind turbines, based in a recent framework used for reconstructing data series of stochastic properties measured at wind turbines. Through a standard fatigue analysis, we show that it…

Data Analysis, Statistics and Probability · Physics 2014-10-30 Pedro G. Lind , Matthias Wächter , Joachim Peinke

Offshore wind turbine towers are pre-assembled and temporarily held in close proximity to each other in group arrangements on port quaysides. Accurate estimates of the aerodynamic loads on the individual towers and on the overall group are…

Fluid Dynamics · Physics 2023-02-23 Claudio Mannini , Tommaso Massai , Andrea Giachetti , Alessandro Giusti

Historically, meteorological and climate studies have been prompted by the need for understanding precipitation to have better logistics in food production. Despite all efforts, nonlinearity in atmosphere dynamics is still a source of…

Analysis of PDEs · Mathematics 2020-07-17 Carla Victoria Valencia-Negrete

Linear and weakly nonlinear stability analyses of an externally shear-imposed, gravity-driven falling film over a uniformly heated wavy substrate are studied. The longwave asymptotic expansion technique is utilized to formulate a single…

Fluid Dynamics · Physics 2024-05-22 Md. Mouzakkir Hossain , Sukhendu Ghosh , Harekrushna Behera , G. P. Raja Sekhar

Vertical profiles for mean wind, standard deviations of velocity fluctuations, and wave-induced part of the momentum flux over a wavy fluid surface are calculated in the Cartesian coordinates on the basis of recent numerical results by…

Atmospheric and Oceanic Physics · Physics 2010-06-21 Vladislav G. Polnikov

Two-dimensional simulations of Rayleigh-B\'enard convection at $Ra = 5\times10^{10}$ show that vertical logarithmic mean temperature profiles can be observed in regions of the boundary layer where thermal plumes are emitted. The profile is…

Many traditional methods for wind turbine design and analysis assume quasi-steady aerodynamics, but atmospheric flows are inherently unsteady and modern turbine blades are susceptible to aeroelastic deformations. This study therefore…

Fluid Dynamics · Physics 2024-06-18 Nathaniel J. Wei , Omkar B. Shende