Rotor aerodynamic loads computation using a constant vorticity contour free wake model

The prediction of vibratory loads on helicopter rotors depends critically on closely coupled interactions between wake-induced aerodynamic loading and structural deformation. Previous rotary wing aerodynamic analyses have typically used models lacking important features of the actual wake structure. This article summarizes the development of a comprehensive analysis of isolated rotors that employs a significantly improved approach to wake simulation. The model discretizes the sheet of vorticity that trails from each blade by laying out vortex filaments along contours of constant sheet strength. In this constant vorticity contour (CVC) wake model, the filaments are composed of curved vortex elements that distort freely in response to the local velocity field. This approach captures the wake of the full span of each rotor blade and includes many features of the complex vorticity field absent from earlier, more simplified models. This article outlines the capabilities of a rotor analysis that incorporates the CVC approach to wake modeling and presents results concentrating on configuration s where wake/blade interaction is of particular importance for modeling unsteady airloads.