Experimental Investigation of Flow Characteristics around a Novel Structure for Passive Flow Control*

A novel structure built of two side walls and a top wall is analyzed to understand its flow control capability. The structure is designed to create control inputs of flow acceleration, deceleration, and vortex generation by manipulating the angle of attack of the top and side walls. Arrays of the structure on a small or micro-scale are expected to decorate a surface to control the flow over it. The current study is performed with a large-scale mock-up of the structure to understand the detailed flow characteristics around it. Twenty variants are 3D printed with different cross-section geometries. The angle of attack of the top and side walls varies between zero, five, and ten degrees both in positive (nozzle-type) and negative directions (diffuser-type). The experiment is conducted in a wind tunnel using 2D Particle Image Velocimetry. Instantaneous and time-averaged velocity, vorticity, and turbulent kinetic energy are investigated. Results show that a flat plate structure perturbs the flow the least. Vortex generation is confirmed from all the variants tested. Additionally, the nozzle-type structures are shown to decelerate airflow through them, while the diffuser-type samples accelerate airflow. Recommendations on an idealized sample geometry for smaller-scale testing are made.