Publication

Interaction of Freestream Turbulence with Vortex Structures in Vertical Axis Turbines

2024

Abstract

We investigate the performance of an H-type vertical axis turbine in a turbulent freestream, focusing on the interaction of the turbulence with the vortical structures created by the turbine. Emphasis is placed on understanding the combined effects of turbulence intensity in the freestream and the turbulence integral scale relative to the generated vortices. A series of regular grids, creating turbulence intensity levels ranging from 3 % to 12 %, and turbulent integral scales that are comparable in size to the leading edge vortex, are placed upstream of the turbine. Turbulence is found to generally increase the performance of the turbine by roughly 30% for tip-speed ratios below the optimal case in a laminar flow. Freestream turbulence was found to generally weaken the leading edge vortex, but also increased the standard deviation of the total forces on the blade.

Official source

https://infoscience.epfl.ch/entities/publication/a88de6f1-7dcf-4ebc-a296-d63efb9ef03d

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2024

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/a88de6f1-7dcf-4ebc-a296-d63efb9ef03d

About this result

Related concepts (32)

Turbulence

In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers. Turbulence is commonly observed in everyday phenomena such as surf, fast flowing rivers, billowing storm clouds, or smoke from a chimney, and most fluid flows occurring in nature or created in engineering applications are turbulent.

Vortex

In fluid dynamics, a vortex (: vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil. Vortices are a major component of turbulent flow. The distribution of velocity, vorticity (the curl of the flow velocity), as well as the concept of circulation are used to characterise vortices.

Boundary layer

In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condition (zero velocity at the wall). The flow velocity then monotonically increases above the surface until it returns to the bulk flow velocity. The thin layer consisting of fluid whose velocity has not yet returned to the bulk flow velocity is called the velocity boundary layer.

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Interaction of Freestream Turbulence with Vortex Structures in Vertical Axis Turbines

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