Some Observations of the Coanda Effect

This chapter elaborates some observations of the Coanda effect. A wall jet flowing over a circular cylinder has replaced the tail rotor on NOTAR type helicopters preventing autorotation. This application is in the presence of an external stream whereupon the Coanda effect becomes synonymous with super-circulation. The "Coanda Effect" is extensively investigated at the University of Arizona, where the initial purpose of the investigation is to determine the effects of streamline curvature on the mean flow and on its turbulence intensities. Moreover, the investigation focuses on the centrifugal instability and the generation of the large stream-wise vortices that eventually lead to the understanding of the separation mechanism of the wall jet from the convex surface. This chapter explores their evolution in the direction of streaming. It is observed that these vortices meander, coalesce, and increase in scale as they move downstream, while the width of the flow and the equivalent turbulent Gortler number also increases.