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.

scholarly journals Computational Characterization of a Rectangular Vortex Generator on a Flat Plate for Different Vane Heights and Angles

2019 ◽  
Vol 9 (5) ◽  
pp. 995 ◽  
Author(s):  
Iosu Ibarra-Udaeta ◽  
Iñigo Errasti ◽  
Unai Fernandez-Gamiz ◽  
Ekaitz Zulueta ◽  
Javier Sancho
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Stokes Equations ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Local Boundary ◽  
Passive Flow Control ◽  
Vortex Size

Vortex generators (VG) are passive flow control devices used for avoiding or delaying the separation of the boundary layer by bringing momentum from the higher layers of the fluid towards the surface. The Vortex generator usually has the same height as the local boundary layer thickness, and these Vortex generators can produce overload drag in some cases. The aim of the present study was to analyze the characteristics and path of the primary vortex produced by a single rectangular vortex generator on a flat plate for the incident angles of β = 10 ∘ , 15 ∘ , 18 ∘ and 20 ∘ . A parametric study of the induced vortex was performed for six VG heights using Reynolds average Navier–Stokes equations at Reynodls number R e = 27,000 based on the local boundary layer thickness, using computational fluid dynamics techniques with OpenFOAM open-source code. In order to determine the vortex size, the so-called half-life radius was computed and compared with experimental data. The results showed a similar trend for all the studied vortex generator heights and incident angles with small variations for the vertical and the lateral paths. Additionally, 0.4H and 0.6H VG heights at incident angles of β = 18 ∘ and β = 20 ∘ showed the best performance in terms of vortex strength and generation of wall shear stress.

scholarly journals Potential of Micro-Vortex Generators in Enhancing the Quality of Flow in a Hypersonic Inlet-Isolator

2020 ◽  
Vol 77 (1) ◽  
pp. 1-10
Author(s):  
Azam Che Idris ◽  
Mohd Rashdan Saad ◽  
Konstantinos Kontis
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Structural Damage ◽  
Vortex Generator ◽  
Transition To Turbulence ◽  
Cruise Missile ◽  
Passive Flow Control ◽  
Attachment Point ◽  
Hypersonic Inlet ◽  
The Impact

The rush to be the first to demonstrate a practical hypersonic cruise missile has never been more frantic among the world’s superpowers, especially since China and India have also announced their own programme. The main hurdle for safe hypersonic flight is the severe shock wave-boundary layer interaction (SWBLI) that could induce flow separation. The separation could lead to inlet unstart and also structural damage at the flow re-attachment point. The simplest method to control these phenomena is by using passive flow control devices such as micro-vortex generator (MVG). The MVG is typically sized in the range of sub-boundary layer and the vortex generated can induce an early transition to turbulence thus avoiding or reducing the impact of flow separation. Many studies have been published with regard to MVG, but most were done in low supersonic speed and not in the hypersonic flow regime. In the current study, the MVG array was placed strategically at various locations on a hypersonic inlet-isolator representative geometry. The MVG has been proven to be very effective in eliminating or reducing the size of flow separation thus reducing the associated peak pressure at the re-attachment point.

scholarly journals Computational modelling of TRIANGULAR sub-boundary-layer vortex generators

2020 ◽  
Vol 307 ◽  
pp. 01054
Author(s):  
Unai Fernandez-Gamiz ◽  
Jon Ruiz de Loizaga ◽  
Iñigo Errasti ◽  
Ana Boyano ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Computational Modelling ◽  
Vortex Generators ◽  
Flow Separation Control ◽  
Local Boundary ◽  
Flow Control Devices ◽  
Manufacture Industry ◽  
Control Devices ◽  
Equal Thickness ◽  
Good Agreement

Vortex generators (VGs) are used increasingly more by the wind turbine manufacture industry as flow control devices to improve rotor blade aerodynamic performance. The VG height is usually designed with equal thickness of the local boundary layer at the VG position. Nevertheless, these conventional VGs may produce excess residual drag in some applications. The so-called sub boundary layer VGs can provide enough momentum transfer over a region several times their own height for effective flow-separation control with much lower drag. The main objective is to investigate how well the simulations can reproduce the physics of the flow of the primary vortex generated by a triangular VG mounted on a flat plate with negligible pressure gradient with the angle of attack of the vane to the oncoming flow β= 18. Three different device heights H= 5mm, H1= 6,25mm, H2= 4,16mm have been studied and compared both qualitatively and quantitatively. To that end, computational simulations have been carried out using RANS method and at Reynolds number Re = 2600 based on the boundary layer momentum thickness θ= 2.4 mm at the VG position. The computational results show good agreement with the experimental data available in AVATAR project.

Supersonic boundary-layer interactions with various micro-vortex generator geometries

2009 ◽  
Vol 113 (1149) ◽  
pp. 683-697 ◽  
Author(s):  
S. Lee ◽  
E. Loth
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Vortex Generator ◽  
Wave Drag ◽  
Supersonic Boundary Layer ◽  
Vortex Generators ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Displacement Thickness ◽  
Mach 3

Abstract Various types of micro-vortex generators (μVGs) are investigated for control of a supersonic turbulent boundary layer subject to an oblique shock impingement, which causes flow separation. The micro-vortex generators are embedded in the boundary layer to avoid excessive wave drag while still creating strong streamwise vortices to energise the boundary layer. Several different types of µVGs were considered including micro-ramps and micro-vanes. These were investigated computationally in a supersonic boundary layer at Mach 3 using monotone integrated large eddy simulations (MILES). The results showed that vortices generated from μVGs can partially eliminate shock induced flow separation and can continue to entrain high momentum flux for boundary-layer recovery downstream. The micro-ramps resulted in thinner downstream displacement thickness in comparison to the micro-vanes. However, the strength of the streamwise vorticity for the micro-ramps decayed faster due to dissipation especially after the shock interaction. In addition, the close spanwise distance between each vortex for the ramp geometry causes the vortex cores to move upwards from the wall due to induced upwash effects. Micro-vanes, on the other hand, yielded an increased spanwise spacing of the streamwise vortices at the point of formation. This resulted in streamwise vortices staying closer to the floor with less circulation decay, and the reduction in overall flow separation is attributed to these effects. Two hybrid concepts, named ‘thick-vane’ and ‘split-ramp’, were also studied where the former is a vane with side supports and the latter has a uniform spacing along the centreline of the baseline ramp. These geometries behaved similar to the micro-vanes in terms of the streamwise vorticity and the ability to reduce flow separation, but are more physically robust than the thin vanes.

scholarly journals AN EXPERIMENTAL STUDY OF THE EFFECT OF VORTEX GENERATOR ON THE FLAT-PLATE BOUNDARY LAYER

2021 ◽  
Vol 13 (2) ◽  
pp. 68-78
Author(s):  
عباس فاضل محمود ◽  
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Flat Plate ◽  
Average Distance ◽  
Plate Boundary ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Stream Velocity ◽  
Drag Coefficients ◽  
Flat Plate Boundary Layer

This paper is dealing with an experimental study to show the influence of the geometric characteristics of the vortex generators VG son the thickness of the boundary layer (∂) and drag coefficients (CD) of the flat plate. Vortex generators work effectively on medium and high angles of attack, since they are "hidden" under the boundary layer and practically ineffective at low angles. The height of VGs relative to the thickness of the boundary layer enables us to study the efficacy of VGs in delaying boundary layer separation. The distance between two VGs also has an effect on the boundary layer if we take into account the interference between two pairs of VGs. The effect of the changing in (h- the height of vortex generator, d- the average distance between tow vortex generators) on the thickness of the flat plate boundary layer and the drag coefficients has been studied for triangular vortex generator. The measurements of the vortex generator have been changed to determine the optimum boundary layer thickness and the change in drag coefficients. An experiment was done at an average free stream velocity, (U∞,) of 28 m/s. The experiment was conducted in the wind tunnel UTAD-2 University (NAU) Kiev, Ukraine.

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.

Wake Characteristics of Vane-Type Vortex Generators in a Flat Plate Laminar Boundary Layer

2015 ◽  
Vol 16 (3) ◽  
pp. 325-338 ◽  
Author(s):  
HoJoon Shim ◽  
Young-Hee Jo ◽  
Kyoungsik Chang ◽  
Ki-Jung Kwon ◽  
Seung-O Park
Keyword(s):  
Boundary Layer ◽  
Flat Plate ◽  
Laminar Boundary Layer ◽  
Vortex Generators ◽  
Wake Characteristics

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.

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