A PHYSICS-BASED MODEL FOR INFLOW CHARACTERISTICS OF MULTI-ROTOR CONFIGURATIONS

A physics-based model for modeling helicopter and autonomous rotor configurations, previously developed for isolated rotors and coaxial rotors in hover and forward flight, has been extended to more general multi-rotor configurations. Simulations for coaxial and tandem rotor configurations have been performed for a number of low and high Reynolds number configurations, and comparisons with test data have been made. The physics behind the rotor interactions has been explored through visualization and analysis of vortex wake structure and inflow velocity distributions. As part of this effort, a fast off-body velocity field analysis that employs GPU processors has been implemented. In addition to computation of inflow velocity field above or below the rotor disks, this approach is capable of rapidly computing and visualizing velocity field on any user specified plane. In many helicopter design studies, the adverse interactions caused by the main rotor wake should be considered in the placement of horizontal and vertical stabilizers, as well as the tail rotors and pusher-propulsors. This capability for rapid calculation and visualization of the off-body flow field would greatly aid the designers in the placement of these components. A previously developed algebraic transition model that regulates the magnitude of the production term in the Spalart-Allmaras one-equation turbulence model has been independently implemented in the present solver. In the present work, this model has been also validated for large scale rotors in hover.Ph.D