Numerical investigation of blade-tip-vortex dynamics

The tip leakage flow affects turbomachines performance generating losses and reducing the effective blading; in addition, unsteady phenomena arise, negatively influencing the machine stability. In this paper, an overview of the existing models is presented. Local measurements of the pressure pulsations, visual flow observations and high quality video recordings from a high speed camera are performed in a novel pump laboratory, which provides the desired visualization of the rotating channels, and allows to study the fluctuating and intermittent nature of this phenomenon, and detect any asymmetry among the channels. A detailed comparison of the vortex tip structure for various tip clearances and with a whole set of numerical simulations finally completes the analysis. The three main focus areas are: tip vortex location, structure and evolution, performance comparison between shrouded and open impeller, at different tip clearance sizes, and study of the rotating instabilities.

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Near Wake Regime Study on Wind Turbine Blade Tip Vortex

Volume 2: Combustion, Fuels, and Emissions; Renewable Energy: Solar and Wind; Inlets and Exhausts; Emerging Technologies: Hybrid Electric Propulsion and Alternate Power Generation; GT Operation and Maintenance; Materials and Manufacturing (Including Coatings, Composites, CMCs, Additive Manufacturing); Analytics and Digital Solutions for Gas Turbines/Rotating Machinery ◽

10.1115/gtindia2019-2493 ◽

2019 ◽

Author(s):

Ojing Siram ◽

Niranjan Sahoo

Keyword(s):

Wind Turbine ◽

Strouhal Number ◽

Vortex Shedding ◽

Flow Condition ◽

Pitch Angle ◽

Tip Vortex ◽

Near Wake ◽

Helical Vortex ◽

Blade Tip ◽

Blade Pitch Angle

Abstract In the present research article results on wind turbine blade tip vortex have been presented, the measurements have been done behind a model scale of horizontal axis wind turbine rotor. The rotor used for flow characterization is a three-bladed having NACA0012 cross-section, the study has been performed for low range tip speed ratio of 0–2 and wind speeds range of 3–6 m/s. The investigation has been conducted specifically to near wake regime, which is often expressed as the region of regular helical vortex structures. Although this nature of regular helical vortex pattern has always been a question of debate with respect to changes in the flow condition, rotor geometry and point of measurements. A systematic experiment was done mainly on the frequency of vortex shedding through hot-wire anemometry (HWA), and the corresponding frequency is express in terms of Strouhal number. Present article work within near wake regime includes tip vortex shedding stability analysis for different blade pitch angle and flow condition. From the systematic experimental observation, the evaluated data indicate that the Strouhal number has an incremental trend when the blade pitch angle is close to 40°, and above it inconsistency in frequency response is observed.

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An Investigation of the Vibratory and Acoustic Benefits Obtainable by the Elimination of the Blade Tip Vortex

Journal of the American Helicopter Society ◽

10.4050/jahs.18.35 ◽

1973 ◽

Vol 18 (4) ◽

pp. 35-44

Author(s):

Richard P. White

Keyword(s):

Tip Vortex ◽

Blade Tip

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Experimental Investigation of the Flow Field of a Ceiling Fan

Volume 3 ◽

10.1115/ht-fed2004-56226 ◽

2004 ◽

Cited By ~ 4

Author(s):

Ankur Jain ◽

Rochan Raj Upadhyay ◽

Samarth Chandra ◽

Manish Saini ◽

Sunil Kale

Keyword(s):

Experimental Investigation ◽

Energy Consumption ◽

Flow Field ◽

Three Dimensional ◽

Flow Characteristics ◽

Tip Vortex ◽

Optimal Designs ◽

Tropical Regions ◽

Fundamental Understanding ◽

Blade Tip

A ceiling fan is the predominating comfort provider in tropical regions worldwide. It consists of an assembly of an electric motor with 3–4 blades suspended from the ceiling of a room. Despite its simplicity and widespread use, the flow induced by a ceiling fan in a closed room has not been investigated, and sub-optimal designs are in wide use. There is vast potential for energy conservation and improved comfort by developing optimized fan designs. This work develops a fundamental understanding of the flow characteristics of a ceiling operating inside a closed room. Using smoke from thick incense sticks, the flow field created by the ceiling fan is visualized. In most regions, the flow is periodic and three-dimensional. Vortices are seen to be attached to the blade tip and hub, which reduces downward flow and increases energy consumption. Only the middle 75% of blade actually pushes the air downwards, and the comfort region is limited to a cylinder directly under the blades; velocities in this region were measured with a vane anemometer. Winglets and spikes attached to the blade tip disrupted the tip vortex, and increased downflow by about 13% without any increase in power consumption.

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