Wake Measurements and Loss Evaluation in a Controlled Diffusion Compressor Cascade

1991 ◽  
Vol 113 (4) ◽  
pp. 591-599 ◽  
Author(s):  
R. P. Shreeve ◽  
Y. Elazar ◽  
J. W. Dreon ◽  
A. Baydar
Keyword(s):  
Large Scale ◽  
Velocity Profiles ◽  
Laser Doppler Velocimeter ◽  
Pressure Probe ◽  
Compressor Cascade ◽  
Near Wake ◽  
Trailing Edge ◽  
Controlled Diffusion ◽  
Edge Surface ◽  
Probe Measurements

The results of two component laser-Doppler velocimeter (LDV) surveys made in the near wake (to one fifth chord) of a controlled diffusion (CD) compressor blade in a large-scale cascade wind tunnel are reported. The measurements were made at three positive incidence angles from near design to angles thought to approach stall. Comparisons were made with calibrated pressure probe and hot-wire wake measurements and good agreement was found. The flow was found to be fully attached at the trailing edge at all incidence angles and the wake profiles were found to be highly skewed. Despite the precision obtained in the wake velocity profiles, the blade loss could not be evaluated accurately without measurements of the pressure field. The blade trailing edge surface pressures and velocity profiles were found to be consistent with downstream pressure probe measurements of loss, allowing conclusions to be drawn concerning the design of the trailing edge.

Wake Measurements and Loss Evaluation in a Controlled Diffusion Compressor Cascade

1990 ◽  
Author(s):  
R. P. Shreeve ◽  
Y. Elazar ◽  
J. W. Dreon ◽  
A. Baydar
Keyword(s):  
Large Scale ◽  
Velocity Profiles ◽  
Laser Doppler Velocimeter ◽  
Pressure Probe ◽  
Compressor Cascade ◽  
Near Wake ◽  
Trailing Edge ◽  
Controlled Diffusion ◽  
Edge Surface ◽  
Probe Measurements

The results of two component laser-Doppler velocimeter (LDV) surveys made in the near wake (to one fifth chord) of a controlled diffusion (CD) compressor blade in a large scale cascade wind tunnel, are reported. The measurements were made at three positive incidence angles from near-design to angles thought to approach stall. Comparisons were made with calibrated pressure probe and hot-wire wake measurements and good agreement was found. The flow was found to be fully attached at the trailing edge at all incidence angles and the wake profiles were found to be highly skewed. Despite the precision obtained in the wake velocity profiles, the blade loss could not be evaluated accurately without measurements of the pressure field. The blade trailing edge surface pressures and velocity profiles were found to be consistent with downstream pressure probe measurements of loss, allowing conclusions to be drawn concerning the design of the trailing edge.

Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage

2010 ◽  
Author(s):  
Hongwei Ma ◽  
Jun Zhang ◽  
Jinghui Zhang ◽  
Zhou Yuan
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
High Loss ◽  
Static Pressure Distribution ◽  
Blade Tip

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade respectively with two tip clearance configurations, including flat tip and grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower spanwise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0° and 5° with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.

Effect of the wing trailing-edge flaps and spoilers position on the jet-vortex wake behind an aircraft during takeoff and landing run

2019 ◽  
pp. 095441001988215
Author(s):  
Yu M Tsirkunov ◽  
MA Lobanova ◽  
AI Tsvetkov ◽  
BA Schepanyuk
Keyword(s):  
Large Scale ◽  
Stokes Equations ◽  
Computational Simulation ◽  
Leading Edge ◽  
Velocity Profiles ◽  
Essential Elements ◽  
Trailing Edge ◽  
Structure Of Flow ◽  
Trailing Edge Flaps ◽  
Calculated Velocity

The large-scale vortex structure of flow in the near wake behind an aircraft during its run on a runway is investigated numerically. The geometrical aircraft configuration was taken close to a mid-range commercial aircraft like Boeing 737-300. It included all essential elements: a body (fuselage), wings with winglets, horizontal and vertical stabilizers, engine nacelles, nacelle pylons, inboard flap track fairings, leading-edge and trailing-edge flaps, and spoilers. The position of flaps and spoilers corresponded to the takeoff and landing run conditions. Computational simulation was based on solving the Reynolds averaged Navier–Stokes equations closed with the Menter Shear Stress Transport turbulence model. Patterns of streamlines, fields of the axial vorticity and the turbulent intensity, vertical and horizontal velocity profiles in the wake are compared and discussed for both run regimes. The flow model was preliminary tested for validity by comparison of the calculated velocity profiles behind a reduced-scale aircraft model with those obtained in special wind tunnel experiments.

Effect of Trailing Edge Suction on Coherent Structures in Near Wake

1998 ◽  
Vol 120 (2) ◽  
pp. 378-384
Author(s):  
S. D. Sharma ◽  
R. K. Sahoo
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Marked Change ◽  
Sampling Technique ◽  
Hot Wire ◽  
Near Wake ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Base Drag ◽  
Vorticity Balance

Experimental results, obtained from hot-wire measurements using a conditional sampling technique, demonstrate feasibility of controlling large-scale spanwise vortices (coherent structures) in the near wake region behind a rectangular base by means of suction through a slit at just one of the trailing edges. The suction thus employed, is found to influence the near wake topology with strong asymmetry and disturb the net vorticity balance. Moreover, a significant reduction in the base drag is achieved as a consequence of the trailing edge suction. The mechanism of the drag reduction is understood to lie in a marked change in the wake dynamics including attenuation in the size and strength of the coherent structures.

The Measurement of Boundary Layers on a Compressor Blade in Cascade: Part 3—Pressure Surface Boundary Layers and the Near Wake

1988 ◽  
Vol 110 (1) ◽  
pp. 146-152 ◽  
Author(s):  
S. Deutsch ◽  
W. C. Zierke
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Velocity Profiles ◽  
Compressor Blade ◽  
Laser Doppler Velocimeter ◽  
Surface Boundary ◽  
Local Pressure ◽  
Near Wake ◽  
Mean Velocity ◽  
Pressure Surface

Using the facility described in Part 1 [23], 11 detailed velocity and turbulence intensity profiles are obtained on the pressure surface of a double circular arc compressor blade in cascade. Two profiles are obtained in the near wake. Laminar boundary layer profiles, which agree well with profiles calculated from Falkner–Skan theory at the local pressure gradient, persist through 57.2 percent chord. The measurements indicate that the onset of transition occurs near 60 percent chord—a value in good agreement with the sublimation flow visualization studies (see Part 1). The lack of a logarithmic region in the data measured at the last chord position (97.9 percent chord) indicates that transition is not complete. The thin laminar boundary layers near the leading edge lead to some measurement problems, which are characterized by large turbulence intensities, in using the laser-Doppler velocimeter (LDV). Close examination of this problem shows that a combination of velocity-gradient broadening and a vibration of the LDV measurement volume causes an elevation of the measured turbulence levels. Fortunately only small errors in mean velocity are introduced. Because of the detached boundary layer on the suction surface, both of the near-wake velocity profiles exhibit regions of backflow. As expected, these near-wake velocity profiles do not exhibit similarity when tested against criteria derived for the far wake.

Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

2021 ◽  
Vol 933 ◽  
Author(s):  
Yong Cao ◽  
Tetsuro Tamura ◽  
Dai Zhou ◽  
Yan Bao ◽  
Zhaolong Han
Keyword(s):  
Large Scale ◽  
Side Wall ◽  
Wake Vortex ◽  
Junction Region ◽  
Near Wake ◽  
Trailing Edge ◽  
Tip Vortices ◽  
Wall Flows ◽  
High Reynolds ◽  
Near Wall

This study topologically describes near-wall flows around a surface-mounted cylinder at a high Reynolds number ( $Re$ ) of $5\times 10^4$ and in a very thick boundary layer, which were partially measured or technically approximated from the literature. For complete and rational flow construction, we use high-resolution simulations and critical-point theory. The large-scale near-wake vortex is composed of two connected segments rolled up from the sides of the cylinder and from the free end. Another large-scale side vortex clearly roots on two notable foci on the lower side wall. In the junction region, the side vortex moves upwards with a curved trajectory, which induces the formation of nodes on the ground surface. In the free-end region, the side vortex is compressed, which results in a smaller trailing-edge vortex and its downstream movement. Only tip vortices are observed in the far wake. The origin of the tip vortices and their distinction from the near-wake vortex are discussed. Further analyses suggest that $Re$ independence should be treated with high caution when $Re$ increases from 500 to ${O}(10^4)$ . The occurrence of upwash flow behind the cylinder strongly depends on the increase in $Re$ , the mechanism of which is also provided. The separation–reattachment process in the junction region and the trailing-edge vortices are discovered only at a high $Re$ . The former should significantly affect the strength of the side vortex in the junction region and the latter should cause a sharp drop in pressure near the trailing edge.

Viscous Flow in a Controlled Diffusion Compressor Cascade With Increasing Incidence

1990 ◽  
Vol 112 (2) ◽  
pp. 256-265 ◽  
Author(s):  
Y. Elazar ◽  
R. P. Shreeve
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Suction Side ◽  
Laminar Separation Bubble ◽  
Compressor Cascade ◽  
Preliminary Assessment ◽  
Near Wake ◽  
Laminar Separation ◽  
Controlled Diffusion ◽  
Flow Through

A detailed two-component LDV mapping of the flow through a controlled diffusion compressor cascade at low Mach number ( ~ 0.25) and Reynolds number of about 7 × 105, at three inlet air angles from design to near stall, is reported. It was found that the suction-side boundary layer reattached turbulent after a laminar separation bubble, and remained attached to the trailing edge even at the highest incidence, at which losses were 3 to 4 times the minimum value for the geometry. Boundary layer thickness increased to fill 20 percent of the blade passage at the highest incidence. Results for pressure-side boundary layer and near-wake also are summarized. Information sufficient to allow preliminary assessment of viscous codes is tabulated.

Characterization of Vortex Dynamics in the Near Wake of an Oscillating Flexible Foil

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Firas F. Siala ◽  
Alexander D. Totpal ◽  
James A. Liburdy
Keyword(s):  
Large Scale ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Wake Flow ◽  
Small Scale ◽  
Mean Flow ◽  
Near Wake ◽  
Trailing Edge ◽  
Swirling Strength ◽  
The Mean

An experimental study was conducted to explore the effect of surface flexibility at the leading and trailing edges on the near-wake flow dynamics of a sinusoidal heaving foil. Midspan particle image velocimetry (PIV) measurements were taken in a closed-loop wind tunnel at a Reynolds number of 25,000 and at a range of reduced frequencies (k = fc/U) from 0.09 to 0.20. Time-resolved and phase-locked measurements are used to describe the mean flow characteristics and phase-averaged vortex structures and their evolution. Large-eddy scale (LES) decomposition and swirling strength analysis are used to quantify the vortical structures. The results demonstrate that trailing edge flexibility has minimal influence on the mean flow characteristics. The mean velocity deficit for the flexible trailing edge and rigid foils remains constant for all reduced frequencies tested. However, the trailing edge flexibility increases the swirling strength of the small-scale structures, resulting in enhanced cross-stream dispersion. Flexibility at the leading edge is shown to generate a large-scale leading edge vortex (LEV) for k ≥ 0.18. This results in a reduction in the swirling strength due to vortex interactions when compared to the flexible trailing edge and rigid foils. Furthermore, it is shown that the large-scale LEV is responsible for extracting a significant portion of energy from the mean flow, reducing the mean flow momentum in the wake. The kinetic energy loss in the wake is shown to scale with the energy content of the LEV.

Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Hongwei Ma ◽  
Jun Zhang ◽  
Jinghui Zhang ◽  
Zhou Yuan
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
High Loss ◽  
Static Pressure Distribution ◽  
Blade Tip

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade, respectively, with two tip-clearance configurations, including the flat tip and the grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower span-wise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0 deg and 5 deg with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.

scholarly journals Viscous Flow in a Controlled Diffusion Compressor Cascade With Increasing Incidence

1989 ◽  
Author(s):  
Y. Elazar ◽  
R. P. Shreeve
Keyword(s):  
Boundary Layer ◽  
Separation Bubble ◽  
Suction Side ◽  
Laminar Separation Bubble ◽  
Compressor Cascade ◽  
Preliminary Assessment ◽  
Near Wake ◽  
Laminar Separation ◽  
Controlled Diffusion ◽  
Flow Through

A detailed two-component LDV mapping of the flow through a controlled diffusion compressor cascade at low Mach number (∼0.25) and Reynolds number of about 7×105, at three inlet air angles from design to near stall, is reported. It was found that the suction side boundary layer reattached turbulent after a laminar separation bubble, and remained attached to the trailing edge even at the highest incidence, at which losses were 3 to 4 times the minimum value for the geometry. Boundary layer thickness increased to fill 20% of the blade passage at the highest incidence. Results for pressure-side boundary layer and near wake are also summarized. Information sufficient to allow preliminary assessment of viscous codes is tabulated.

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