Mean and turbulence measurements in the near field of a wingtip vortex

Chow, Jim; Zilliac, Gregory G.; Bradshaw, P.

doi:10.2514/3.13712

Cited by 47 publications

(69 citation statements)

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“…This also confirms the statement by Chow et al (1997a), that the angle of attack is the key parameter that influences the core axial velocity (Reynolds number and Aspect Ratio (AR) were also found to influence the core axial velocity). As the vortex progressed downstream the core axial velocity slowly returned towards free-stream velocity for both the wake-like and jet-like cases.…”

Section: Discussionsupporting

confidence: 77%

“…One of the most important experimental wing-tip vortex studies in the nearfield was conducted by Chow et al (1997b) (see also Chow et al (1997a)), which has been used to validate the majority of numerical investigations in the last 10 years Blaisdell, 2009, 2013;Craft et al, 2006;Dacles-Mariani et al, 1995;Kim and Rhee, 2005;Revell and Iaccarino, 2006;Uzun et al, 2006).…”

Section: Experimental Investigations Of Wing-tip Vortices In the Nearmentioning

confidence: 99%

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Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

O’Regan

Griffin

Young

2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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Section: Discussionsupporting

confidence: 77%

Section: Experimental Investigations Of Wing-tip Vortices In the Nearmentioning

confidence: 99%

Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

O’Regan

Griffin

Young

2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…A case in point are vortical flows, in which the Reynolds stresses are known to lag the mean strain field. 18 A simple expression for C EQ can be obtained from the well-known G-locus of equilibrium boundary layers proposed by Clauser. 16 The source term implementation is presented in Equation 3 where S VG represents the source term itself:…”

Section: Source Term Implementationmentioning

confidence: 99%

An integral boundary layer engineering model for vortex generators implemented in XFOIL

2018

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To assess and optimize vortex generators (VGs) for flow separation control, the effect of these devices should be modelled in a cost and time efficient way. Therefore, it is of interest to extend integral boundary layer models to analyse the effect of VGs on airfoil performance. In this work, the turbulent boundary layer formulation is modified using a source term approach. An additional term is added to the shear-lag equation, to account for the increased dissipation due to streamwise vortex action in the boundary layer, forcing transition at the VG leading edge where applicable. The source term is calibrated and a semi-empirical relation is set up and implemented in XFOIL. The modified code is capable of addressing the effect of the VG height, length, inflow angle, and chordwise position on the airfoil's aerodynamic properties. The predicted polars for airfoils with VGs show a good agreement with reference data, and the code robustness is demonstrated by assessing different airfoil families at a wide range of Reynolds numbers. KEYWORDSintegral boundary layer, separation control, source term, vortex generator, Xfoil INTRODUCTIONFor the next generation of wind turbines, manufacturers aim to design multimegawatt rotors to improve the competitiveness of wind energy technology. To up-scale wind turbines, novel technologies are required and new design challenges will appear. One such aerodynamic challenge is the management of separated flow. Preventing or at least delaying separation over the blades can positively affect the annual energy production (AEP).On top of that, the magnitude and severe variations of the aerodynamic loads associated with separating flows can be reduced, mitigating structural fatigue issues. In the wind energy industry, separation control is often realized by using passive vortex generators (VGs).Vortex generators improve the resistance of a boundary layer against flow separation by re-energizing the flow close to the surface. The streamwise vortices shed from the free tips of the VGs enhance mixing between the high-energy flow in the outer part of the boundary layer with the low-energy regions near the walls (see Schubauer and Spangenberg. 1 ) The physics involved is nontrivial and poses a number of modelling challenges.To achieve a cost-effective scale up of current turbines, it will become necessary to evolve towards a multidisciplinary design process where VGs are already incorporated early in the design phase. To assess and optimize the use of VGs, there will be a need to effectively model these devices in a cost and time efficient manner. BackgroundNumerous VG modelling techniques have been explored in literature, most of which use computational fluid dynamics (CFD). The most direct and intuitive approach is to model the effect of VGs by including them as a local geometrical protrusion in the domain. This approach requires a fully . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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“…To illustrate the various steps of the procedure for constructing a high-order mesh, we will employ a simple geometrical domain that consists of an unswept wing of rectangular planform composed of NACA0012 aerofoil sections and a round tip, essentially a wing tip, enclosed in a rectangular box. This geometry is also of aerodynamic interest as a case study of vortex roll-up proposed and experimentally measured by Chow et al [11] which has been used in CFD validation studies, see for instance [12].…”

Section: Linear Mesh Generation Via the 3d Medial Objectmentioning

confidence: 99%

High-order curvilinear hybrid mesh generation for CFD simulations

Marcon

Turner

Peiró

et al. 2018

2018 AIAA Aerospace Sciences Meeting

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We describe a semi-structured method for the generation of high-order hybrid meshes suited for the simulation of high Reynolds number flows. This is achieved through the use of highly stretched elements in the viscous boundary layers near the wall surfaces. CADfix is used to first repair any possible defects in the CAD geometry and then generate a medial object based decomposition of the domain that wraps the wall boundaries with partitions suitable for the generation of either prismatic or hexahedral elements. The latter is a novel distinctive feature of the method that permits to obtain well-shaped hexahedral meshes at corners or junctions in the boundary layer. The medial object approach allows greater control on the "thickness" of the boundary-layer mesh than is generally achievable with advancing layer techniques. CADfix subsequently generates a hybrid straight-sided mesh of prismatic and hexahedral elements in the near-field region modelling the boundary layer, and tetrahedral elements in the far-field region covering the rest of the domain. The mesh in the near-field region provides a framework that facilitates the generation, via an isoparametric technique, of layers of highly stretched elements with a distribution of points in the direction normal to the wall tailored to efficiently and accurately capture the flow in the boundary layer. The final step is the generation of a high-order mesh using NekMesh, a high-order mesh generator within the Nektar++ framework. NekMesh uses the CADfix API as a geometry engine that handles all the geometrical queries to the CAD geometry required during the high-order mesh generation process. We will describe in some detail the methodology using a simple geometry, a NACA wing tip, for illustrative purposes. Finally, we will present two examples of application to reasonably complex geometries proposed by NASA as CFD validation cases: the Common Research Model and the Rotor 67.

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Mean and turbulence measurements in the near field of a wingtip vortex

Cited by 47 publications

References 0 publications

Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

Numerical and experimental investigation of the mean and turbulent characteristics of a wing-tip vortex in the near field

An integral boundary layer engineering model for vortex generators implemented in XFOIL

High-order curvilinear hybrid mesh generation for CFD simulations

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