Experimental investigation of Vortex Generator and Gurney Flap performance effect under dynamic stall and rotational effects

• Applicant: Dr.-Ing. Christian Nayeri
• Subject Area: Fluid Mechanics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446073296

Robust, effective and easily implemented passive flow control devices such as vortex generators (VG) and Gurney Flaps (GF) are particularly appealing for wind turbine applications where increased performance and longevity is sought after. However, one of the particularities of wind turbines is that they operate in turbulent conditions and as a result experience dynamic stall. This renders all passive flow control device studies performed under static conditions rather limited with regard to their applicability. Furthermore, rotational effects on wind turbine blades play a crucial role and no complete investigation should exclude them. Although some relevant research has been conducted in a helicopter rotor frame, wind turbines face specific challenges (e.g., different turbulence time scales, increased blade thickness, constantly separated radial flow) that call for dedicated tests on wind turbine models. Additionally, research in combined VG and GF application is scarce and practically non-existent in a dynamic stall or rotating blade frame. The proposed project aims at progressing beyond the current state of the art and by covering the aforementioned knowledge gaps. This will be achieved by performing an extended wind tunnel study on pitching airfoils equipped with VGs and GFs and on a three meter small horizontal axis wind turbine model (BeRT) also equipped with passive flow control devices.The investigation is directly relevant to current full-scale small wind turbines and is the first step towards the combined application of VGs and GFs to large wind turbines.The objectives of the proposed investigation are to:1. Explore an effective VG configuration for a wind turbine airfoil experiencing dynamic stall.2. Find an optimal GF configuration for a wind turbine airfoil experiencing dynamic stall.3. Find the best way to combine the positive effects of VGs and GFs for a wind turbine airfoil experiencing dynamic stall.4. Study the flow past the selected VG, GF and VG + GF configurations on the actual wind turbine model BeRT in a wind tunnel.5. Generate a broad and accurate experimental data base that will be used to validate numerical models of the effect of VGs and GFs in the future.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Christian Oliver Paschereit