An experimental and computational study of flow over a NACA 0021 airfoil with wavy leading edge modification

Flow control by means of tubercles, which are spanwise-periodic protrusions observed on the Humpback whale's flippers, has been previously shown to exhibit beneficial aerodynamic traits. Understanding the mechanism that yields the desirable results among nominally two-dimensional airfoils has led to the design of an alternative leading edge configuration. In the present work, this novel variation on tubercles was employed to modify a NACA 0021 airfoil for wind tunnel pressure measurement tests in the transitional flow regime. In addition, a Computation Fluid Dynamics study was performed using the SST transitional model in the context of unsteady RANS at several attack angles. The results from the numerical investigation are in reasonable agreement with those of the experiments, and suggest the presence of features that are also observed in flows over tubercled foils, most notably a distinct pair of streamwise vortices for each wavelength of the tubercle-like feature.