Measurement of the flow field around straight-bladed vertical axis wind turbine

• No yaw mechanisms are required and low transmission losses.
• Wind velocities around the VAWT are measured using the LDV system.
• The reverse flow is generated at some region of downstream region.
• Large turbulence intensity is generated in the plane of wind turbine rotation.
• The turbulence intensity decreases with the increase of tip speed ratio.

The flow field around a vertical axis wind turbine (VAWT) is very complicated mainly due to the continuous variation of the geometrical angle of attack and resultant flow velocity to blade during rotation. This paper has attempted to compile the assessment study the flow field around a small straight-bladed VAWT. Two dimensional unsteady flows around the VAWT are investigated through the use of the Laser Doppler Velocimeter (LDV) system, operating at three different tip speed ratios in wind tunnel experiments. Meanwhile, the geometrical angles of attack and the resultant flow velocities are calculated using local wind velocity and direction. From the results of these experiments, it has been found that a wide low wind velocity field emerges in the wind turbine׳s internal region and continues into the downstream region. As the tip speed ratio increases, the area of low wind velocity also expands. Furthermore, moving from the upstream to the downstream region, the velocity deficit becomes greater in the free stream direction. Finally, large turbulence intensity is generated in the plane of wind turbine rotation.