Comparative effects of vortex generators on Ahmed’s squareback and minivan car models

2017 ◽  
Vol 231 (9) ◽  
pp. 1287-1293 ◽  
Author(s):  
Antoine Evrard ◽  
Olivier Cadot ◽  
Christophe Sicot ◽  
Vincent Herbert ◽  
Denis Ricot ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Car Model ◽  
Bubble Length ◽  
Base Drag ◽  
Scale Roughness ◽  
Ahmed Body

This work aims to evaluate the base suction and drag modifications caused by a boundary layer manipulation due to large scale roughness prior its salient separation. A real car model, a Peugeot 208, and a squareback Ahmed body are both tested and compared in a scale 1 wind tunnel at 120 km/h with road effect and rotating wheels. The roughnesses are vortex generators placed in the boundary layer that develops on the roof of the model. They produce longitudinal vortices in the free shear. Two types of vortex generators are used, wall mounted cylinders for weak disturbances and inclined blades for stronger disturbances. It is found that whatever the vehicle is, the drag is always increased. For the squareback Ahmed body, the base suction is decreased with similar magnitudes for both vortex generators showing a beneficial effect of the vortex generator on the base drag. On the contrary, the base suction is always increased for the real car whatever the vortex generators used. In that case the effects of magnitude depends on the vortex generator types. While the cylinders degrade slightly the base suction with almost no modification in the wake, the blades are able to reduce considerably the bubble length causing a huge increase in drag, lift and base suction.

Steady longitudinal vortices in supersonic turbulent separated flows

2011 ◽  
Vol 672 ◽  
pp. 451-476 ◽  
Author(s):  
ERICH SCHÜLEIN ◽  
VICTOR M. TROFIMOV
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Roughness Element ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Leading Edge ◽  
Separated Flows ◽  
Vortex Generators ◽  
Longitudinal Vortices ◽  
Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

scholarly journals Numerical Simulation of the Boundary Layer Control on the NACA 0015 Airfoil Through Vortex Generators

2020 ◽  
Author(s):  
Douglas da Silva ◽  
Vinicius Malatesta
Keyword(s):  
Boundary Layer ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Boundary Layer Control ◽  
Recirculation Bubble ◽  
Longitudinal Vortices ◽  
Before And After ◽  
Drag And Lift ◽  
Naca 0015 ◽  
Layer Control

This paper studies the influence caused by a vortex generator (VG) on a wing section with NACA 0015 airfoil when this generator is located before and after a recirculation bubble caused by the boundary layer detachment. The study was numerically carried out and concentrated under conditions of flow with Rec = 2.38 × 105 and angles of attack AoA = 3 and 6, characterized by the fact that they undergo detachment of the boundary layer before and after the location of the VG, respectively. The use of the generator in AoA = 3 strongly influenced the reduction of the recirculation bubble, leading to a drag reduction of 1.43%. In AoA = 6 with a bubble recirculation, the effect was much lower, with no well-defined formation of longitudinal vortices, resulting in increased drag and lift at 0.33 and 0.35%, respectively.

Flow Physics of a Race Car Wing With Vortex Generators in Ground Effect

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Yuichi Kuya ◽  
Kenji Takeda ◽  
Xin Zhang ◽  
Scott Beeton ◽  
Ted Pandaleon
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Vortex Generator ◽  
Ground Effect ◽  
Surface Flow ◽  
Vortex Generators ◽  
Separation Control ◽  
Race Car ◽  
Horseshoe Vortices ◽  
Large Scale Vortex

This paper experimentally investigates the use of vortex generators for separation control on an inverted wing in ground effect using off-surface flow measurements and surface flow visualization. A typical racing car wing geometry is tested in a rolling road wind tunnel over a wide range of incidences and ride heights. Rectangular vane type of sub-boundary layer and large-scale vortex generators are attached to the suction surface, comprising counter-rotating and corotating configurations. The effects of both device height and spacing are examined. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators suppress the flow separation at the center of each device pair, while the counter-rotating large-scale vortex generators induce horseshoe vortices between each device where the flow is separated. The corotating sub-boundary layer vortex generators tested here show little evidence of separation control. Increasing the spacing of the counter-rotating sublayer vortex generator induces significant horseshoe vortices, comparable to those seen in the counter-rotating large-scale vortex generator case. Wake surveys show significant spanwise variance behind the wing equipped with the counter-rotating large-scale vortex generators, while the counter-rotating sub-boundary layer vortex generator configuration shows a relatively small variance in the spanwise direction. The flow characteristics revealed here suggest that counter-rotating sub-boundary layer vortex generators can provide effective separation control for race car wings in ground effect.

Computational Investigation of a Race Car Wing With Vortex Generators in Ground Effect

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Yuichi Kuya ◽  
Kenji Takeda ◽  
Xin Zhang
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Flow Separation ◽  
Large Scale ◽  
Vortex Generator ◽  
Ground Effect ◽  
Experimental Results ◽  
Vortex Generators ◽  
Flow Physics ◽  
Large Scale Vortex

Vortex generators can be applied to control separation in flows with adverse pressure gradients, such as wings. In this paper, a study using three-dimensional steady computations for an inverted wing with vortex generators in ground effect is described. The main aim is to provide understanding of the flow physics of the vortex generators, and how they affect the overall aerodynamic performance of the wing to complement previous experimental studies of the same configuration. Rectangular vane type sub-boundary layer and large-scale vortex generators are attached to the suction surface of the wing, including both counter-rotating and co-rotating configurations. In order to provide confidence, Reynolds-averaged Navier–Stokes simulations using the Spalart–Allmaras turbulence model are validated against the experimental results regarding force, pressure, and wake characteristics, with the validation exhibiting close agreement with the experimental results. The streamwise friction shows the downwash induced by the generated vortex acts to suppress flow separation. The flow field survey downstream of the vortex generators features breakdown and dominance of the generated vortex in the flow. The vortex generated by the counter-rotating sub-boundary layer vortex generator grows in size and breaks down as it develops downstream, while the vortex generated by the counter-rotating large-scale vortex generator shows high vorticity even further downstream, indicating the persistence of the vortex in the flow. The flow field behind the co-rotating sub-boundary layer vortex generator is dominated by a lateral flow, having the spanwise flow component rather than a swirling flow, and the vortex quickly dissipating as it develops downstream. The results from this paper complement previous experimental measurements by highlighting the flow physics of how vortex generators can help control flow separation for an inverted wing in ground effect, and how critical vortex generator type and size are for its effectiveness.

Flow Separation Control on a Race Car Wing With Vortex Generators in Ground Effect

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Yuichi Kuya ◽  
Kenji Takeda ◽  
Xin Zhang ◽  
Scott Beeton ◽  
Ted Pandaleon
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Large Scale ◽  
Vortex Generator ◽  
Ground Effect ◽  
Vortex Generators ◽  
Separation Control ◽  
Suction Surface ◽  
Flow Separation Control ◽  
Generator Type

Flow separation control using vortex generators on an inverted wing in ground effect is experimentally investigated, and its performance is characterized in terms of forces and pressure distributions over a range of incidence and ride height. Counter-rotating and co-rotating rectangular-vane type vortex generators are tested on the suction surface of the wing. The effect of device height and spacing is investigated. The counter-rotating sub-boundary layer vortex generators and counter-rotating large-scale vortex generators on the wing deliver 23% and 10% improvements in the maximum downforce, respectively, compared with the clean wing, at an incidence of one degree, and delay the onset of the downforce reduction phenomenon. The counter-rotating sub-boundary layer vortex generators exhibit up to 26% improvement in downforce and 10% improvement in aerodynamic efficiency at low ride heights. Chordwise pressure measurement confirms that both counter-rotating vortex generator configurations suppress flow separation, while the co-rotating vortex generators exhibit negligible effectiveness. This work shows that a use of vortex generators, notably of the counter-rotating sub-boundary layer vortex generator type, can be effective at controlling flow separation, with a resultant improvement in downforce for relatively low drag penalty.

Control of Separated Boundary-Layer on Subsonic Airfoil Using Vortex Generator Jet Devices

2006 ◽  
Author(s):  
A. Kourta ◽  
G. Petit ◽  
J. C. Courty ◽  
J. P. Rosenblum
Keyword(s):  
Boundary Layer ◽  
Friction Coefficient ◽  
Skin Friction ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Leading Edge ◽  
Skin Friction Coefficient ◽  
Synthetic Jets ◽  
High Lift ◽  
Longitudinal Vortices

The control of subsonic high lift induced separation on airfoil may improve the flight envelope of current aircraft or even simplify the complex and heavy high-lift devices on commercial airframes. Until now, synthetic jets have proved a really interesting efficiency to delay or remove even leading-edge located separated areas on high-lift configuration but are not efficient for real scale aircrafts. In case of pressure-like separation (i.e. from trailing-edge), synthetic jets can be replaced by so the called “Vortex Generator Jets” which create strong longitudinal vortices that increase mixing in inner boundary layer and consequently the skin friction coefficient is increased to prevent separation. In this study, numerical simulations were undertaken on a generic three dimensional flat plate in order to quantify the effect of the longitudinal vortices on the natural skin friction coefficient. Both counter and co-rotative devices were tested at different exhaust velocities and distances between each others. Finally co-rotative vortex generators jets were tested on a three dimensional generic airfoil ONERA D. Results show a delay of the separation occurence but this solution does not seem to be as robust as synthetic jets. The study of jets spacing with respect to the efficiency of the devices shows a maximum for a given ratio of spacing to exhaust velocity.

scholarly journals Computational Modelling of Three Different Sub-Boundary Layer Vortex Generators on a Flat Plate

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3107 ◽  
Author(s):  
Ruben Gutierrez-Amo ◽  
Unai Fernandez-Gamiz ◽  
Iñigo Errasti ◽  
Ekaitz Zulueta
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Flow Separation ◽  
Computational Modelling ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Primary Vortex ◽  
Good Efficiency ◽  
Local Boundary ◽  
Passive Flow Control

Flow separation is the source of several problems in a wind turbine including load fluctuations, lift losses, and vibrations. Vortex generators (VGs) are passive flow control devices used to delay flow separation, but their implementation may produce overload drag at the blade section where they are placed. In the current work, a computational model of different geometries of vortex generators placed on a flat plate has been carried out throughout fully meshed computational simulations using Reynolds Averaged Navier-Stokes (RANS) equations performed at a Reynolds number of R e θ = 2600 based on local boundary layer (BL) momentum thickness θ = 2.4 mm. A flow characterization of the wake behind the vortex generator has been done with the aim of evaluating the performance of three vortex generator geometries, namely Rectangular VG, Triangular VG, and Symmetrical VG NACA0012. The location of the primary vortex has been evaluated by the vertical and lateral trajectories and it has been found that for all analyzed VG geometries the primary vortex is developed below the boundary layer thickness δ = 20 mm for a similar vorticity level ( w x m a x ). Two innovative parameters have been developed in the present work for evaluating the vortex size and the vortex strength: Half-Life Surface S 05 and Mean Positive Circulation Γ 05 + . As a result, an assessment of the VG performance has been carried out by all analyzed parameters and the symmetrical vortex generator NACA0012 has provided good efficiency in energy transfer compared with the Rectangular VG.

The Response of Injection of Vortex Generator Jets to a Backward Facing Step Flow

2003 ◽  
Author(s):  
Koichi Yamagata ◽  
Manabu Saito ◽  
Tadashi Morioka ◽  
Shinji Honami
Keyword(s):  
Shear Layer ◽  
Large Scale ◽  
Flow Behavior ◽  
Velocity Ratio ◽  
Vortex Generator ◽  
Step Response ◽  
Backward Facing Step ◽  
Longitudinal Vortices ◽  
Step Flow ◽  
Vortex Generator Jets

In this paper, the flow behavior of a reattachment process over a backward facing step flow is reported. The reattachment process is controlled by injection of vortex generator jets. The injection of jets upstream of the step produces the co-rotating longitudinal vortices in a separating shear layer. The experiment of the step response of the injection jet is also conducted in order to investigate the evolution process of the longitudinal vortices. A large scale of primary and counter vortices are observed, when the velocity ratio of the free stream to injected jet is 6. The detailed structure of the longitudinal vortices is clarified. The remarkable effect of the vortices on the separating shear layer downstream of the step is observed.

Application of Boundary Layer Fences and Vortex Generators in Improving Performance of S-Duct Diffusers

2001 ◽  
Vol 124 (1) ◽  
pp. 136-142 ◽  
Author(s):  
R. K. Sullerey ◽  
Sourabh Mishra ◽  
A. M. Pradeep
Keyword(s):  
Boundary Layer ◽  
Total Pressure ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Pressure Rise ◽  
Vortex Generator ◽  
Substantial Improvement ◽  
Vortex Generators ◽  
Flow Distortion ◽  
Flow Quality

An experimental investigation was undertaken to study the effect of various fences and vortex generator configurations in reducing the exit flow distortion and improving total pressure recovery in two-dimensional S-duct diffusers of different radius ratios. Detailed measurements including total pressure and velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken in a uniform inlet flow at a Reynolds number of 7.8×105. These measurements are presented here along with static pressure rise, distortion coefficient, and the transverse velocity vectors at the duct exit determined from the measured data. The results indicate that substantial improvement in static pressure rise and flow quality is possible with judicious deployment of fences and vortex generators.

scholarly journals Heat Transfer Characteristic on Wing Pairs Vortex Generator using 3D Simulation of Computational Fluid Dynamic

2021 ◽  
Vol 3 (2) ◽  
pp. 215-224
Author(s):  
Petrus Setyo Prabowo ◽  
◽  
Stefan Mardikus ◽  
Ewaldus Credo Eukharisto ◽  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Vortex Generator ◽  
Transfer Characteristic ◽  
Vortex Generators ◽  
Working Fluid ◽  
Longitudinal Vortices ◽  
Delta Winglet ◽  
Fluid Flow Characteristics

Vortex generators are addition surface that can increase heat transfer area and change the fluid flow characteristics of the working fluid to increase heat transfer coefficient. The use of vortex generators produces longitudinal vortices that can increase the heat transfer performance because of the low pressure behind vortex generators. This investigation used delta winglet vortex generator that was combined with rectangular vortex generator to Reynold numbers ranging 6,000 to 10,000. The parameters of Nusselt number, friction factor, velocity vector and temperature distribution will be evaluated.

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