CFD analysis of a Coanda jet in a crossflow over a NACA 0012 airfoil




Janecka, Matthew Ryan

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A Coanda jet exposed to a crossflow is examined via RANS simulations with a particular focus on rolling moments. The wing employed in the study is a NACA 0012 profile with an aspect ratio of 1. The Coanda surface is formed by a revolution of the NACA 0012 profile at the tip of the wing. The Reynolds number of the crossflow is 5 × 10⁵ and angle of attack is 2 degrees. The rolling moments generated by the Coanda jet are compared to those estimated from a theoretical aileron that spans half the length of the wing with a 25 percent chord. Theory indicates that a blowing factor, (Cᵤ /α) [superscript (2/3)], of 1.13 corresponds to a control surface deflection of approximately 10.7 degrees. Furthermore, scaling laws apply to the rolling moments and lift forces for low blowing factors. At higher values of the blowing factor, secondary vortices form in the wake of the Coanda jet which cause the scaling laws to fail. In addition, a qualitative analysis is conducted which shows the formation of wing tip vortices and their evolution in the streamwise direction. A secondary vortex forms as a result of the Coanda jet detaching and reattaching to the Coanda surface. Lastly, it is seen that the Wray-Agarwal-RCM turbulence model exhibits much better convergence properties than the Spalart-Allmaras-RCM, and based on comparisons with previous studies, is thought to be the more accurate model.


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