Flow control on a high thickness airfoil by a trapped vortex cavity.

This paper summarises the experimental campaign performed at CIRA CT-1 wind tunnel aimed to investigate the potential benefit obtainable using a trapping vortex cell system on a high thickness airfoil with and without steady suction and/or injection mass flow. The behaviour of a 2D model, equipped with a span wise oriented circular cavity, has been investigated. Pressure distribution on the model surface and inside the cavity and the complete flow field around the model and inside the cavity have been measured. An extensive test campaign has been carried out in the CT-1, an open circuit wind tunnel, with test section size of 305x305x600 mm 3 and maximum speed of 55 m/s. Due to the limited dimensions of the WT, the model has been mounted on the bottom wall of the wind tunnel in order to avoid blockage problems. The model represents a two dimensional high thickness airfoil with a chord length of 350mm. The model angle of attack ranges between 5.66° to 12.66° with a step of 1°. The installation of the model on the wind tunnel bottom wall presented heavy flow instability under the front part of the model. The flow instability has been solved applying a flow suction in front the model trough a porous wall installed on the bottom WT wall. The cavity has been realized with transparent material in order to allow optical access and consequently PIV measurements. The model has been designed in order to permit flow suction and/or blowing inside the cavity. The influence of different parameters has been investigated. Tests have been performed varying the wind tunnel speed (form 15 m/s, to 30 m/s), varying the suction mass flow (from 0 m 3 /h to 25 m 3 /h) varying the blowing mass flow (from 0 m 3 /h to 50 m 3 /h) applying suction and blowing at the same time, and varying the model angle of attack (AoA). In the paper the performed test campaign, the adopted experimental set-up, the data post-processing and the results' description are reported.