An extension of a strong viscous–inviscid coupling method for modeling the effects of vortex generators

Abstract

The aim of this work is to provide insights into the advantages and the limitations of the extension of a strong viscous-inviscid interactive code for modeling the effects of vortex generators, with focus on the calibration and validation for wind turbine airfoils. The proposed methodology relies on the approach proposed by other authors in the past and introduces an alternative formulation for the lag dissipation within the integral boundary-layer equations whose effects on the numerical prediction are evaluated. Besides the verification of the aeronautical test cases, particular attention is devoted to the validation of the results for several airfoils commonly used in wind turbine design. A blind test for airfoils from an industrial test case is conducted as well. Results show that the maximum lift coefficient can be well predicted by the present implementation, whereas the angle of maximum lift is a little higher than in wind tunnel measurements. Apart from that, the drag coefficients of airfoils with vortex generators cannot be predicted by the current implementation, but it is expected that the maximum lift and the stall angle of attack are more important in the design phase, since they determine power, loads, and noise.

Modelling dynamic stall of an airfoil with vortex generators using a double-wake panel model with viscous-inviscid interaction

“…Kerho and Kramer 30 proposed introducing VG-added mixing into the boundary layer to the inviscid-viscous coupled code Xfoil through modifying the stress transport equation to mimic the behaviors of VGs. Daniele et al 31 suggested a sin-exponential increment instead of a step change in 30 , which was shown a good agreement with experimental results and increased numerical stability. De Tavernier 32 further extended Kerho and Kramer's approach 30 by introducing a smooth step function and decay rate to the source strength term to Xfoil 33 .…”

Modeling dynamic stall of an airfoil with vortex generators using a double‐wake panel model with viscous–inviscid interaction

“…Kerho and Kramer 34 proposed introducing VG‐added mixing into the boundary layer to the inviscid‐viscous coupled code Xfoil through modifying the stress transport equation to mimic the behaviors of VGs. Daniele et al 35 suggested a sin‐exponential increment instead of a step change in Kerho and Kramer, 34 which was shown a good agreement with experimental results and increased numerical stability. De Tavernier et al 36 further extended Kerho and Kramer's approach 34 by introducing a smooth step function and decay rate to the source strength term to Xfoil 37 …”

Numerical/experimental investigations on reducing drag penalty of passive vortex generators on a NACA 4415 airfoil

“…As a rotating machine, the maximum Reynolds number of a wind turbine is proportional to the blade radius (it reaches up to Re = 25 × 10 6 in giant windmills) . In these cases, airfoils exhibit better performance, such as higher lift coefficient and lower drag ones, resulting in larger lift‐to‐drag ratio at a given angle of attack . However, to succeed in this performance improvement, one has to design VG's height according to the local boundary layer thickness.…”