On the identification of a vortex

TL;DR: In this paper, the authors provide a detailed two-dimensional numerical analysis of the physical phenomena occurring during dynamic stall of a Darrieus wind turbine, which is particularly complex because as the turbine rotates, the incidence angle and the blade Reynolds number vary, causing unsteady effects in the flow field.

Abstract: The aim of this work is to provide a detailed two-dimensional numerical analysis of the physical phenomena occurring during dynamic stall of a Darrieus wind turbine. The flow is particularly complex because as the turbine rotates, the incidence angle and the blade Reynolds number vary, causing unsteady effects in the flow field. At low tip speed ratio, a deep dynamic stall occurs on blades, leading to large hysteresis lift and drag loops (primary effects). On the other hand, high tip speed ratio corresponds to attached boundary layers on blades (secondary effects). The optimal efficiency occurs in the middle range of the tip speed ratio where primary and secondary effects cohabit. To prove the capacity of the modeling to handle the physics in the whole range of operating condition, it is chosen to consider two tip speed ratios (λ=2 and λ=7), the first in the primary effect region and the second in the secondary effect region. The numerical analysis is performed with an explicit, compressible RANS k-ω code TURBFLOW , in a multiblock structured mesh configuration. The time step and grid refinement sensitivities are examined. Results are compared qualitatively with the visualization of the vortex shedding of Brochier (1986, "Water channel experiments of dynamic stall on Darrieus wind turbine blades," J. Propul. Power, 2(5), pp. 445-449). Hysteresis lift and drag curves are compared with the data of Laneville and Vitecoq (1986, "Dynamic stall: the case of the vertical axis wind turbine," Prog. Aerosp. Sci., 32, pp. 523-573).

TL;DR: In this paper, the authors used the large eddy simulation (LES) methodology to investigate how turbulent mixing can be enhanced by varying the angle between the jet and the oncoming cross-flow.

TL;DR: An improved method for stream surface computation that delivers accurate results in regions of intricate flow is presented, along with a novel method to determine boundary surfaces of vortex cores.

TL;DR: In this paper, the authors present a reference record created on 2005-11-18, modified on 2016-08-08 and used for the analysis of turbulence and transport in the context of energie.

TL;DR: In this paper, the basic equations of fluid mechanics are stated, with enough derivation to make them plausible but with-out rigour, and the physical meanings of the terms in the equations are explained.

TL;DR: In this article, the authors discuss the Reynolds equations and estimate of the Reynolds stress in the kinetic theory of gases, and describe the effects of shear flow near a rigid wall.

TL;DR: In this article, the probability density, Fourier transforms and characteristic functions, joint statistics and statistical independence, Correlation functions and spectra, the central limit theorem, and the relation functions are discussed.