Spatiotemporal analysis of fluctuating base pressure and velocity in a blunt trailing edge wake

2016 ◽  
Author(s):  
Heather A. Clark ◽  
Philippe Lavoie
Keyword(s):  
Spatiotemporal Analysis ◽  
Base Pressure ◽  
Trailing Edge ◽  
Blunt Trailing Edge

The Effect of Base Bleed on the Flow behind a Two-Dimensional Model with a Blunt Trailing Edge

1967 ◽  
Vol 18 (3) ◽  
pp. 207-224 ◽  
Author(s):  
P. W. Bearman
Keyword(s):  
Vortex Formation ◽  
Reynolds Numbers ◽  
Base Pressure ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Trailing Edge ◽  
Model Base ◽  
Blunt Trailing Edge ◽  
Two Dimensional Model ◽  
Base Bleed

SummaryThe effects of base bleed on the flow about a two-dimensional model with a blunt trailing edge were examined at Reynolds numbers, based on model base height, between 1·3×104 and 4·1×104. The ratio of boundary layer thickness at the trailing edge to half the model base height was approximately 0·4. Measurements were made of base pressure, vortex shedding frequency and the distance to vortex formation. With a sufficiently large bleed quantity the regular vortex street pattern disappeared and the base drag of the section was reduced to about a third of its value without bleed. The base pressure was found to vary linearly with the inverse of the vortex formation distance. Results of a previous splitter plate investigation were found to agree closely with those of the present experiments.

A study of three-dimensional aspects of vortex shedding from a bluff body with a mild geometric disturbance

1997 ◽  
Vol 330 ◽  
pp. 85-112 ◽  
Author(s):  
N. TOMBAZIS ◽  
P. W. BEARMAN
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Vortex Formation ◽  
Three Dimensional ◽  
Base Pressure ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Trailing Edges ◽  
Mode Transitions

Experiments have been carried out to study the three-dimensional characteristics of vortex shedding from a half-ellipse shape with a blunt trailing edge. In order to control the occurrence of vortex dislocations, the trailing edges of the models used were constructed with a series of periodic waves across their spans. Flow visualization was carried out in a water tunnel at a Reynolds number of 2500, based on trailing-edge thickness. A number of shedding modes were observed and the sequence of mode transitions recorded. Quantitative data were obtained from wind tunnel measurements performed at a Reynolds number of 40000. Two shedding frequencies were recorded with the higher frequency occurring at spanwise positions coinciding with minima in the chord. At these same positions the base pressure was lowest and the vortex formation length longest. Arguments are put forward to explain these observations. It is shown that the concept of a universal Strouhal number holds, even when the flow is three-dimensional. The spanwise variation in time-average base pressure is predicted using the estimated amount of time the flow spends at the two shedding frequencies.

The effect of base bleed on vortex shedding and base pressure in compressible flow

1981 ◽  
Vol 110 ◽  
pp. 273-292 ◽  
Author(s):  
F. Motallebi ◽  
J. F. Norbury
Keyword(s):  
Supersonic Flow ◽  
Compressible Flow ◽  
Vortex Shedding ◽  
Transonic Flow ◽  
Vortex Formation ◽  
Base Pressure ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Base Bleed ◽  
The Relationship

Experiments have been carried out to investigate the phenomenon of vortex shedding from the blunt trailing edge of an aerodynamic body in transonic and supersonic flow. The effect of a discharge of bleed air from a slot in the trailing edge has been included and the relationship between the vortex formation and base pressure has been considered.In transonic flow a small amount of bleed air was found to produce a rearward shift in the point of origin of the vortices with a consequent substantial increase in base pressure. The effect was less marked in supersonic flow. At higher rates of bleed two different regimes of vortex shedding were identified and increase in bleed rate caused a reduction in base pressure. For bleed rates giving near-maximum base pressure no vortex shedding occurred.

A Method for Reducing the Base Drag of Wings with Blunt Trailing Edge

1972 ◽  
Vol 23 (1) ◽  
pp. 15-23 ◽  
Author(s):  
M Tanner
Keyword(s):  
Aspect Ratio ◽  
Base Pressure ◽  
Wind Tunnels ◽  
Trailing Edge ◽  
Total Drag ◽  
Blunt Trailing Edge ◽  
The Mean ◽  
Drag And Lift ◽  
Base Drag ◽  
Local Base

SummaryTo study the possibilities of reducing the base drag of profiles with a blunt trailing edge, experiments were performed in two low-speed wind-tunnels at the DFVLR-AVA, Göttingen, some on models between walls and some on rectangular wings with an aspect ratio of 2.5. The results show that the mean base pressure can be increased, and so the base drag reduced, by using a special form of the blunt trailing edge. The variation of local base pressure along the span, and the way in which this variation is influenced by the form of the trailing edge, is also shown. Some results for the total drag and lift are also indicated.

Flow behind castellated blunt-trailing-edge aerofoils at supersonic speeds

1998 ◽  
Vol 375 ◽  
pp. 85-111 ◽  
Author(s):  
E. C. MAGI ◽  
S. L. GAI
Keyword(s):  
Quantitative Data ◽  
Base Pressure ◽  
Qualitative Description ◽  
Wake Flow ◽  
Spanwise Direction ◽  
Pressure Measurements ◽  
Near Wake ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
The Mean

A study of the near-wake flow of castellated blunt-trailing-edge aerofoils at a Mach number of 2 was conducted to understand the nature of the flow and the mechanisms of base pressure recovery. The investigation has shown that strong gradients exist in the spanwise direction and that the formation of the wake recompression shock occurs further away from the wake axis. Also, the wake neck is broader and diffused. Detailed quantitative data involving pressure measurements, schlieren and holographic interferometry, and laser transit velocimetry, are presented. A theoretical model to predict the mean base pressure on a castellated base is also proposed. Comparison with experimental data shows that the model provides a qualitative description of the flow behind a castellated base at supersonic speeds.

Analysis of Blunt Trailing Edge Airfoils

2003 ◽  
Author(s):  
K. J. Standish ◽  
C. P. van Dam
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Computational Techniques ◽  
Wind Turbine Blades ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Large Wind ◽  
Structural Volume

The adoption of blunt trailing edge airfoils for the inner regions of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide increased structural volume, but have also been found to improve the lift characteristics of airfoils and therefore allow for section shapes with a greater maximum thickness. Limited experimental data makes it difficult for wind turbine designers to consider and conduct tradeoff studies using these section shapes. This lack of experimental data precipitated the present analysis of blunt trailing edge airfoils using computational fluid dynamics. Several computational techniques are applied including a viscous/inviscid interaction method and several Reynolds-averaged Navier-Stokes methods.

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