Twin test 3 of TWEET-IE project: Micro devices for enhanced performance of airfoil sections

The present dataset refers to a Twin Test, as part of the TWEET-IE project (TWEET-IE : Twin Wind tunnels for Energy and the EnvironmenT - Innovations and Excellence, HORIZON-WIDERA-2021-ACCESS-03-01 / PR# 101079125), carried out in the wind tunnels of the Politecnico di Milano (POLIMI) and the National Technical University of Athens (NTUA). In this Twin Test, wind tunnel tests were conducted assessing the effect of micro devices for enhanced performance of flatback (FB) airfoil sections. FB airfoils, i.e. thick airfoils with a blunt trailing edge (TE) are used near the root region of modern wind turbine blades, as they provide several benefits compared to their thin TE counterparts. The utter goal of the tests was to investigate the effect of freestream turbulence intensity, Reynolds number and blockage ratio on airfoil performance, 3D flow separation and wake behaviour. Additionally, the effect of flow control devices regarding flow separation control and drag reduction were assessed. The NTUA tests consist of surface pressure measurements, hot-wire measurements, flow visualization with tufts and Stereo Particle Image Velocimetry (SPIV) measurements. The pressure measurements allow for determining the basic performance characteristics of the airfoil, and the hot-wire measurements provide information about the primal shedding frequency.The POLIMI tests consist of surface pressure measurements, force balance and hot-wire measurements. The pressure measurements allow for determining the basic performance characteristics of the airfoil as well as comparing facilities. Next, the force balance measurements provide insights on the effect of the 3D separation to the airfoil loads and the hot-wire measurements allow for determining the spanwise wake correlations. Both fixed and free boundary layer transition cases were tested at a Reynolds number of Re = 1.25M.