Experimental Investigation of Unsteady Laminar-to-Turbulent Transition over a Wind Turbine Blade Section

Authors

1 Aerospace Engineering Department, University of Tehran

2 Mechanical Engineering Department, University of Kashan

10.22044/jsfm.2026.15494.3924

Abstract

In the present study, an experimental investigation of the laminar-to-turbulent transition of flow over the surface of a wind turbine airfoil section has been conducted. For this purpose, the Reynolds number range for the experiments was set between 0.13 and 0.53 million, and the angle of attack of the airfoil model was varied from -4 to 14 degrees. The experimental tests were performed on a model airfoil representing the blade section of a 660 kW wind turbine under static conditions. The measurement of the transition onset point was examined using various methods based on the output of pressure sensors and hot-film sensors. Two novel techniques based on the frequency analysis of hot-film signals were introduced and evaluated for determining the transition onset point. The results indicate that all the employed methods exhibit good agreement in identifying the transition onset point. As velocity and angle of attack increase, the transition onset moves backward and approach model’s leading edge. Furthermore, the analysis of the separation bubble location reveals that at high angles of attack, the position of the separation bubble onset varies over time, leading to temporal variations in the spatial location of the flow transition onset. The temporal variations in the onset point of the separation bubble can be effectively observed through the 180-degree phase change between consecutive upstream and downstream hot-film sensors.

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Journal of Solid and Fluid Mechanics
Volume 16, Issue 1
May and June 2026
Pages 41-62

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