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

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 Reθ = 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 (wxmax). Two innovative parameters have been developed in the present work for evaluating the vortex size and the vortex strength: Half-Life Surface S05 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.

[1]  John Fulker,et al.  Research at DERA on sub boundary layer vortex generators (SBVGs) , 2001 .

[2]  A. Hadjadj,et al.  Boundary layer transition over a concave surface caused by centrifugal instabilities , 2018, Computers & Fluids.

[3]  Eduard Egusquiza,et al.  Comparison of four different models of vortex generators , 2012 .

[4]  D. Baldacchino,et al.  Towards integral boundary layer modelling of vane-type vortex generators , 2015 .

[5]  Mac Gaunaa,et al.  The Effect of Mounting Vortex Generators on the DTU 10MW Reference Wind Turbine Blade , 2014 .

[6]  Andrew L. Heyes,et al.  Modification of a wing tip vortex by vortex generators , 2005 .

[7]  Ekaitz Zulueta Guerrero,et al.  ESTADO DEL ARTE SOBRE DISPOSITIVOS ACTIVOS Y PASIVOS DE CONTROL DE FLUJO PARA TURBINAS EÓLICAS , 2016 .

[8]  Niels N. Sørensen,et al.  Simulations of wind turbine rotor with vortex generators , 2016 .

[9]  Ekaitz Zulueta,et al.  Computational characterization of the vortex generated by a Vortex Generator on a flat plate for different vane angles , 2017 .

[10]  Tim P. Bray.  A parametric study of vane and air-jet vortex generators , 1998 .

[11]  John C. Lin,et al.  Review of research on low-profile vortex generators to control boundary-layer separation , 2002 .

[12]  Andrew W. Fitzgibbon,et al.  Direct least squares fitting of ellipses , 1996, Proceedings of 13th International Conference on Pattern Recognition.

[13]  U. Fernández-Gámiz,et al.  Computational study of the vortex path variation with the VG height , 2014 .

[14]  John K. Eaton,et al.  Interaction Between a Vortex and a Turbulent Boundary Layer. Part 1: Mean Flow Evolution and Turbulence Properties , 1987 .

[15]  T. L. Sullivan.  Effect of vortex generators on the power conversion performance and structural dynamic loads of the Mod-2 wind turbine , 1984 .

[16]  Ekaitz Zulueta,et al.  Five Megawatt Wind Turbine Power Output Improvements by Passive Flow Control Devices , 2017 .

[17]  Niels N. Sørensen,et al.  Prediction of the Effect of Vortex Generators on Airfoil Performance , 2014 .

[18]  Oscar Barambones,et al.  Computational Modelling of Rectangular Sub-Boundary Layer Vortex Generators , 2018 .

[19]  Clara Marika Velte,et al.  Investigation of flow behind vortex generators by stereo particle image velocimetry on a thick airfoil near stall , 2013 .

[20]  Ekaitz Zulueta,et al.  Flow Control Devices for Wind Turbines , 2017 .

[21]  Eduard Egusquiza,et al.  Testing of self-similarity and helical symmetry in vortex generator flow simulations , 2016 .

[22]  Michel Stanislas,et al.  Control of a decelerating boundary layer. Part 1: Optimization of passive vortex generators , 2006 .

[23]  L. Richardson,et al.  The Deferred Approach to the Limit. Part I. Single Lattice. Part II. Interpenetrating Lattices , 1927 .

[24]  Brian G. Allan,et al.  Flow-Field Measurement of Device-Induced Embedded Streamwise Vortex on a Flat Plate , 2002 .

[25]  C. Velte.  Vortex Generator Flow Model Based on Self-Similarity , 2013, 1906.06396.

[26]  Clara Marika Velte,et al.  Aerodynamically shaped vortex generators , 2016 .

[27]  F. Menter.  Two-equation eddy-viscosity turbulence models for engineering applications , 1994 .

[28]  Ekaitz Zulueta,et al.  Parametric study of low-profile vortex generators , 2017 .

[29]  R. Gutiérrez,et al.  Non-conventional vortex generators calculated with CFD , 2018, Journal of Physics: Conference Series.

[30]  Savvas A. Tassou,et al.  A Review of Airside Heat Transfer Augmentation with Vortex Generators on Heat Transfer Surface , 2018, Energies.