Some Aspects of the Aerodynamics of Gurney Flaps on a Double-Element Wing

2000 ◽  
Vol 123 (1) ◽  
pp. 99-104 ◽  
Author(s):  
David Jeffrey ◽  
Xin Zhang ◽  
David W. Hurst
Keyword(s):  
Laser Doppler Anemometry ◽  
Separated Flow ◽  
Surface Flow ◽  
Wake Flow ◽  
Single Element ◽  
Suction Surface ◽  
Gurney Flaps ◽  
Gurney Flap ◽  
Flow Features ◽  
Flap Deflection

Gurney flaps of different heights have been fitted to a generic double-element wing, and the effects at two typical flap angles have been observed using force and pressure measurements, and by performing flow surveys using Laser Doppler Anemometry. At a low flap setting angle of 20 deg the suction-surface flow remains attached to the trailing edge of the flap, and vortex flow features and perturbation velocities are all similar to those observed when Gurney flaps are fitted to single element wings. At a high flap deflection of 50 deg there is an extensive region of separated flow over the flap, yet the Gurney flap still alters the flow structure. The measurements suggest that the wake flow behind the Gurney flap consists of a von Karman vortex street of alternately shed vortices. The effects of the Gurney flap on the lift, zero-lift drag, and pressure distributions are reported, and the differences between the trends observed for single-element wings are discussed.

Some features of steady separated flow from low speed to hypersonic

2008 ◽  
Vol 112 (1128) ◽  
pp. 109-113
Author(s):  
S. L. Gai
Keyword(s):  
Shear Layer ◽  
Bluff Body ◽  
Separated Flow ◽  
Base Flow ◽  
The Body ◽  
Wake Flow ◽  
Recirculating Flow ◽  
Flow Features ◽  
Hypersonic Speeds ◽  
Low Speeds

Steady non-vortex shedding base flow behind a bluff body is considered. Such a flow is characterised by the flow separation at the trailing edge of the body with an emerging shear layer which reattaches on the axis with strong recompression and recirculating flow bounded by the base, the shear layer, and the axis. Steady wake flows behind a bluff body at low speeds have been studied for more than a century (for example, Kirchhoff; Riabouchinsky). Recently, research on steady bluff body wake flow at low speeds has been reviewed and reinterpreted by Roshko. Roshko has also commented on some basic aspects of steady supersonic base flow following on from Chapman and Korst analyses. In the present paper, we examine the steady base flow features both at low speeds and supersonic speeds in the light of Roshko’s model and expand on some further aspects of base flows at supersonic and hypersonic speeds, not covered by Roshko.

scholarly journals Characteristics of Boundary-Layer Transition and Reynolds-Number Sensitivity of Three-Dimensional Wings of Varying Complexity Operating in Ground Effect

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Luke S. Roberts ◽  
Mark V. Finnis ◽  
Kevin Knowles
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Separation Bubble ◽  
Ground Effect ◽  
Surface Flow ◽  
Boundary Layer Transition ◽  
Single Element ◽  
Suction Surface ◽  
Layer Transition ◽  
Reynolds Number Dependency

The influence of Reynolds number on the aerodynamic characteristics of various wing geometries was investigated through wind-tunnel experimentation. The test models represented racing car front wings of varying complexity: from a simple single-element wing to a highly complex 2009-specification formula-one wing. The aim was to investigate the influence of boundary-layer transition and Reynolds-number dependency of each wing configuration. The single-element wing showed significant Reynolds-number dependency, with up to 320% and 35% difference in downforce and drag, respectively, for a chordwise Reynolds number difference of 0.81 × 105. Across the same test range, the multi-element configuration of the same wing and the F1 wing displayed less than 6% difference in downforce and drag. Surface-flow visualization conducted at various Reynolds numbers and ground clearances showed that the separation bubble that forms on the suction surface of the wing changes in both size and location. As Reynolds number decreased, the bubble moved upstream and increased in size, while reducing ground clearance caused the bubble to move upstream and decrease in size. The fundamental characteristics of boundary layer transition on the front wing of a monoposto racing car have been established.

An Experimental Investigation of Suction Surface Flow Features on a High-Lift LPT

2008 ◽  
Author(s):  
Mark McQuilling ◽  
Mitch Wolff ◽  
Sergey Fonov ◽  
Jim Crafton ◽  
Rolf Sondergaard
Keyword(s):  
Experimental Investigation ◽  
Surface Flow ◽  
Suction Surface ◽  
High Lift ◽  
Flow Features

Investigation of the three-dimensional flow over a 40° swept wing

2011 ◽  
Vol 115 (1169) ◽  
pp. 441-449 ◽  
Author(s):  
S. Zhang ◽  
A. J. Jaworski ◽  
J. T. Turner ◽  
N. J. Wood
Keyword(s):  
Boundary Layer ◽  
Laser Doppler Anemometry ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Angle Of Incidence ◽  
Swept Wing ◽  
Suction Surface ◽  
Vortical Structures

AbstractThree-component laser Doppler anemometry (LDA) has been used to measure the complex flow distributions over the suction surface of a symmetrical 40°swept wing model at an angle of incidence of 9° and for the relatively low Reynolds number (based on the root chord) of 2·1 × 105. Emphasis was placed on the separation and reattachment of the boundary-layer flow, and the formation of vortical structures.The experimental programme now described utilised a large wind tunnel and several advanced measurement techniques to produce an unusually detailed collection of results. Thus, data are presented here for the behaviour of the three-dimensional boundary layer developing on the suction surface at positions from 30% to 90% semi-span. These results show the spatial variations of the time-averaged mean and fluctuating velocity components in three orthogonal directions, including the distributions of the normal and shear stress levels. Further analysis has enabled the time-averaged vortical structures to be identified and compared with the results of surface flow visualisation.Flow over a swept wing poses many challenges for the computational modeller. The underlying aim, here, therefore, was to produce a data archive for the validation of computer predictions. As will be shown, some of the experimental results have already been used in this way and the data base is available for use by other workers.

Measurement of surface flow features at the stagnation region of a swept cylinder

1994 ◽  
Author(s):  
S. Mangalam ◽  
S. Venkateswaran ◽  
S. Korategere
Keyword(s):  
Surface Flow ◽  
Stagnation Region ◽  
Flow Features

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

scholarly journals Urban Boundary Layers Over Dense and Tall Canopies

2021 ◽  
Author(s):  
Alexandros Makedonas ◽  
Matteo Carpentieri ◽  
Marco Placidi
Keyword(s):  
Packing Density ◽  
Laser Doppler Anemometry ◽  
Canopy Height ◽  
Roughness Sublayer ◽  
Average Height ◽  
Wind Tunnel Experiments ◽  
Mean Velocity ◽  
Flow Features ◽  
Stress Layer ◽  
Density Results

AbstractWind-tunnel experiments were carried out on four urban morphologies: two tall canopies with uniform height and two super-tall canopies with a large variation in element heights (where the maximum element height is more than double the average canopy height, $$h_{max}=2.5h_{avg}$$ h max = 2.5 h avg ). The average canopy height and packing density are fixed across the surfaces to $$h_{avg} = 80~\hbox {mm}$$ h avg = 80 mm , and $$\lambda _{p} = 0.44$$ λ p = 0.44 , respectively. A combination of laser Doppler anemometry and direct-drag measurements are used to calculate and scale the mean velocity profiles with the boundary-layer depth $$\delta $$ δ . In the uniform-height experiment, the high packing density results in a ‘skimming flow’ regime with very little flow penetration into the canopy. This leads to a surprisingly shallow roughness sublayer (depth $$\approx 1.15h_{avg}$$ ≈ 1.15 h avg ), and a well-defined inertial sublayer above it. In the heterogeneous-height canopies, despite the same packing density and average height, the flow features are significantly different. The height heterogeneity enhances mixing, thus encouraging deep flow penetration into the canopy. A deeper roughness sublayer is found to exist extending up to just above the tallest element height (corresponding to $$z/h_{avg} = 2.85$$ z / h avg = 2.85 ), which is found to be the dominant length scale controlling the flow behaviour. Results point toward the existence of a constant-stress layer for all surfaces considered herein despite the severity of the surface roughness ($$\delta /h_{avg} = 3 - 6.25$$ δ / h avg = 3 - 6.25 ). This contrasts with the previous literature.

Measurements of turbulent crossflow separation created by a curved body of revolution

2007 ◽  
Vol 589 ◽  
pp. 353-374 ◽  
Author(s):  
P. A. GREGORY ◽  
P. N. JOUBERT ◽  
M. S. CHONG
Keyword(s):  
Flow Visualization ◽  
Skin Friction ◽  
Cross Sections ◽  
Separated Flow ◽  
Surface Flow ◽  
The Body ◽  
Body Of Revolution ◽  
Outer Flow ◽  
Friction Measurements ◽  
Surface Flow Visualization

Using the method pioneered by Gurzhienko (1934), the crossflow separation produced by a body of revolution in a steady turn is examined using a stationary deformed body placed in a wind tunnel. The body of revolution was deformed about a radius equal to three times the body's length. Surface pressure and skin-friction measurements revealed regions of separated flow occurring over the rear of the model. Extensive surface flow visualization showed the presence of separated flow bounded by a separation and reattachment line. This region of separated flow began just beyond the midpoint of the length of the body, which was consistent with the skin-friction data. Extensive turbulence measurements were performed at four cross-sections through the wake including two stations located beyond the length of the model. These measurements revealed the location of the off-body vortex, the levels of turbulent kinetic energy within the shear layer producing the off-body vorticity and the large values of 〈uw〉 stress within the wake. Velocity spectra measurements taken at several points in the wake show evidence of the inertial sublayer. Finally, surface flow topologies and outer-flow topologies are suggested based on the results of the surface flow visualization.

Measurements of Secondary Losses in a Turbine Cascade With the Implementation of Nonaxisymmetric Endwall Contouring

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
D. C. Knezevici ◽  
S. A. Sjolander ◽  
T. J. Praisner ◽  
E. Allen-Bradley ◽  
E. A. Grover
Keyword(s):  
Kinetic Energy ◽  
Axial Flow ◽  
Surface Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Suction Surface ◽  
Blade Passage ◽  
Low Pressure Turbine ◽  
Endwall Contouring ◽  
Pressure And Velocity Measurements

An approach to endwall contouring has been developed with the goal of reducing secondary losses in highly loaded axial flow turbines. The present paper describes an experimental assessment of the performance of the contouring approach implemented in a low-speed linear cascade test facility. The study examines the secondary flows of a cascade composed of Pratt & Whitney PAKB airfoils. This airfoil has been used extensively in low-pressure turbine research, and the present work adds intrapassage pressure and velocity measurements to the existing database. The cascade was tested at design incidence and at an inlet Reynolds number of 126,000 based on inlet midspan velocity and axial chord. Quantitative results include seven-hole pneumatic probe pressure measurements downstream of the cascade to assess blade row losses and detailed seven-hole probe measurements within the blade passage to track the progression of flow structures. Qualitative results take the form of oil surface flow visualization on the endwall and blade suction surface. The application of endwall contouring resulted in lower secondary losses and a reduction in secondary kinetic energy associated with pitchwise flow near the endwall and spanwise flow up the suction surface within the blade passage. The mechanism of loss reduction is discussed in regard to the reduction in secondary kinetic energy.

scholarly journals Unsteady pressure measurement and numerical simulations in an end-wall region of a linear blade cascade

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Erik Flídr ◽  
Petr Straka ◽  
Milan Kladrubský ◽  
Tomáš Jelínek
Keyword(s):  
Numerical Simulations ◽  
Pressure Measurement ◽  
Power Spectra ◽  
Surface Flow ◽  
Wall Region ◽  
Suction Surface ◽  
Flow Angle ◽  
Unsteady Pressure ◽  
Flow Visualizations ◽  
End Wall

AbstractThis contribution describes experimental and numerical research of an unsteady behaviour of a flow in an end-wall region of a linear nozzle cascade. Effects of compressibility ($$M_\mathrm {2,is}$$ M 2 , is ) and inlet flow angle ($$\alpha _1$$ α 1 ) were investigated. Reynolds number ($$Re_\mathrm {2,is}$$ R e 2 , is $$=8.5\times 10^5$$ = 8.5 × 10 5 ) was held constant for all tested cases. Unsteady pressure measurement was performed at the blade mid-span in the identical position $${\mathfrak {s}}$$ s to obtain reference data. Surface flow visualizations were performed as well as the steady pressure measurement to support conclusions obtained from the unsteady measurements. Comparison of the surface Mach number distributions obtained from the experiments and from the numerical simulations are presented. Flow visualizations are then compared with calculated limiting streamlines on the blade suction surface. It was shown, that the flow structures in the end-wall region were not affected by the primary flow at the blade mid-span, even when the shock wave formed. This conclusion was made from the experimental, numerical, steady as well as unsteady points of view. Three significant frequencies in the power spectra suggested that there was a periodical interaction between the vortex structures in the end-wall region. Based on the data analyses, anisotropic turbulence was observed in the cascade.

Sign in / Sign up

Export Citation Format

Share Document