Effect of Trailing Edge Geometry on Vortex Shedding and Acoustic Radiation

2002 ◽  
Author(s):  
Claudia Kunze ◽  
Denis Lynch ◽  
Thomas Mueller ◽  
William Blake
Keyword(s):  
Vortex Shedding ◽  
Acoustic Radiation ◽  
Trailing Edge ◽  
Edge Geometry

Influence of Trailing-Edge Geometry on Hydraulic-Turbine-Blade Vibration Resulting From Vortex Excitation

1960 ◽  
Vol 82 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Gunnar Heskestad ◽  
D. R. Olberts
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Vortex Shedding ◽  
Hydraulic Turbine ◽  
Trailing Edge ◽  
Blade Vibration ◽  
Edge Geometry ◽  
Blade Thickness ◽  
Vortex Induced Vibrations ◽  
Approach Velocity

A study was made to determine effects of trailing-edge geometry on the vortex-induced vibrations of a model blade designed to simulate the conditions at the trailing edge of a hydraulic-turbine blade. For the type of trailing-edge flow encountered, characterized by a thick boundary layer relative to the blade thickness, the vortex-shedding frequency could not be represented by any modification of the Strouhal formula. The amplitude of the induced vibrations increased with the strength of a vortex in the von Karman vortex street of the wake; one exception was provided by a grooved edge, which is discussed in some detail. For a particular approach velocity, the vortex strength is primarily a function of the ratio of distance between separation points to boundary-layer thickness, the degree of “shielding” between regions of vortex growth, and frequency of vortex shedding.

Particle Image Velocimetry Measurements of Wake Flows of Various Bridge Sections

2006 ◽  
Author(s):  
Emanuela Palombi ◽  
Gregory A. Kopp ◽  
Roi Gurka
Keyword(s):  
Particle Image Velocimetry ◽  
Vortex Shedding ◽  
Particle Image ◽  
Uniform Flow ◽  
Pressure Measurements ◽  
Trailing Edge ◽  
Wake Flows ◽  
Edge Geometry ◽  
Image Velocimetry ◽  
The Mean

Using Particle Image Velocimetry (PIV) we investigate the influence of leading and trailing edge geometry on the wake flows of various elongated cylinders in smooth uniform flow. The results present a comparison between the mean wake flows, as well as the vortex shedding activity found to occur in each case. Pressure measurements were recorded on the surface of the cylinders to examine the corresponding fluctuating and mean forces exhibited by each model tested. Significant variations in the wake topology and aerodynamic behaviour of the four cylinder geometries tested were observed.

Some modeling issues on trailing-edge vortex shedding

AIAA Journal ◽  
2001 ◽  
Vol 39 ◽  
pp. 787-793
Author(s):  
Wei Ning ◽  
Li He
Keyword(s):  
Vortex Shedding ◽  
Trailing Edge ◽  
Edge Vortex

Computational Study of the Risø-B1-18 Airfoil with a Hinged Flap Providing Variable Trailing Edge Geometry

2005 ◽  
Vol 29 (2) ◽  
pp. 89-113 ◽  
Author(s):  
Niels Troldborg
Keyword(s):  
Reynolds Number ◽  
Unsteady Flow ◽  
Computational Study ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Flow Conditions ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Edge Geometry ◽  
Fully Developed Turbulent Flow

A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Risø-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades. It is concluded that a moderately curved flap with flap chord to airfoil curve ratio between 0.05 and 0.10 would be an optimum choice.

Vortex Shedding Analysis in the Wake of a Flat Plate at Low Incidence and Low Reynolds Number

2021 ◽  
Author(s):  
Bastav Borah ◽  
Anand Verma ◽  
Vinayak Kulkarni ◽  
Ujjwal K. Saha
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Flat Plate ◽  
Vortex Shedding ◽  
Low Reynolds Number ◽  
General Tendency ◽  
Flat Plates ◽  
Trailing Edge ◽  
Low Reynolds ◽  
Low Incidence

Abstract Vortex shedding phenomenon leads to a number of different features such as flow induced vibrations, fluid mixing, heat transfer and noise generation. With respect to aerodynamic application, the intensity of vortex shedding and the size of vortices play an essential role in the generation of lift and drag forces on an airfoil. The flat plates are known to have a better lift-to-drag ratio than conventional airfoils at low Reynolds number (Re). A better understanding of the shedding behavior will help aerodynamicists to implement flat plates at low Re specific applications such as fixed-wing micro air vehicle (MAV). In the present study, the shedding of vortices in the wake of a flat plate at low incidence has been studied experimentally in a low-speed subsonic wind tunnel at a Re of 5 × 104. The velocity field in the wake of the plate is measured using a hot wire anemometer. These measurements are taken at specific points in the wake across the flow direction and above the suction side of the flat plate. The velocity field is found to oscillate with one dominant frequency of fluctuation. The Strouhal number (St), calculated from this frequency, is computed for different angles of attack (AoA). The shedding frequency of vortices from the trailing edge of the flat plate has a general tendency to increase with AoA. In this paper, the generation and subsequent shedding of leading edge and trailing edge vortices in the wake of a flat plate are discussed.

Sound diffraction at a trailing edge

1981 ◽  
Vol 108 ◽  
pp. 443-460 ◽  
Author(s):  
S. W. Rienstra
Keyword(s):  
Vortex Shedding ◽  
Pulse Wave ◽  
Layer Structure ◽  
Harmonic Wave ◽  
Sound Field ◽  
Edge Condition ◽  
Trailing Edge ◽  
Kutta Condition ◽  
High Reynolds ◽  
Sound Diffraction

The diffraction of externally generated sound in a uniformly moving flow at the trailing edge of a semi-infinite flat plate is studied. In particular, the coupling of the sound field to the hydrodynamic field by way of vortex shedding from the edge is considered in detail, both in inviscid and in viscous flow.In the inviscid model the (two-dimensional) diffracted fields of a cylindrical pulse wave, a plane harmonic wave and a plane pulse wave are calculated. The viscous proess of vortex shedding is represented by an appropriate trailing-edge condition. Two specific cases are compared, in one of which the full Kutta condition is applied, and in the other no vortex shedding is permitted. The results show good agreement with Heavens’ (1978) observations from his schlieren photographs, and confirm his conclusions. It is further demonstrated, by an explicit expression, that the sound power absorbed by the wake may be positive or negative, depending on Mach number and source position. So the process of vortex shedding does not necessarily imply an attenuation of the sound.In the viscous model a high-Reynolds-number approximation is constructed, based on a triple-deck boundary-layer structure, matching the harmonic plane wave outer solution to a known incompressible inner solution near the edge, to obtain the viscous correction to the Kutta condition.

PIV Analysis on the Effect of Stator Loading on Transonic Blade-Row Interactions

2010 ◽  
Author(s):  
Scott B. Reynolds ◽  
Steven E. Gorrell ◽  
Jordi Estevadeordal
Keyword(s):  
Vortex Shedding ◽  
Bow Shock ◽  
Trailing Edge ◽  
Shock Interactions ◽  
Transonic Compressor ◽  
Close Spacing ◽  
Topological Features ◽  
Blade Row ◽  
Vortex Size ◽  
Increased Strength

Experiments have been performed to investigate interactions between a loaded stator and transonic rotor. The Blade Row Interaction (BRI) rig is used to simulate an embedded transonic fan stage with realistic geometry (thin trailing edge) which produces a wake through diffusion. Details of the unsteady flow field between the stator and rotor were obtained using PIV. Flow-visualization images and PIV data that facilitate analysis of vortex shedding, wake motion, and wake-shock-interaction phenomena are presented. Stator wake and rotor-bow-shock interactions are analyzed for three stator/rotor axial spacings, and two stator loadings. Specific shed vortices and wake topological features are isolated for each configuration. The data analysis focuses on measuring the vortex size, strength, and location as it forms on the stator trailing edge and propagates downstream into the rotor passage. It was observed that vortex shedding is synchronized to the passing of a rotor bow shock. Results show that the circulation of a vortex increased by 19 to 23% from far to close spacing due to the increased strength of the rotor bow shock impacting the stator trailing edge. Reduction in stator loading decreased shed vortex circulation for the same stator/rotor axial spacing by 20 to 25%. Pitchwise radius of vortices also decreased by 13 to 19% from far to close spacing. Such changes in vortex size and strength should be accounted for to predict the effect of unsteady blade-row interactions on transonic compressor performance.

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