LORAAX: LOw Reynolds number Aircraft Aerodynamics with Xfoil
LORAAX is a 3D panel code fully coupled with a 2D integral boundary layer method (Xfoil). Unlike traditional panel methods, It can predict nonlinearities in the lift and pitching moment curves due to the onset of stall, separation bubbles, and laminar-turbulent transition. Xfoil boundary layer calculations are performed on the fly via the libxfoil library. Subsonic compressibility effects are accounted for through the Prandtl-Glauert transformation. LORAAX is not limited to a planar wake; the wake can be optionally deformed to the correct force-free shape as part of the iterative solution. Since the boundary layer method assumes 2D flow, only 0-sideslip conditions are currently supported, and accuracy will suffer for very low aspect ratios and/or highly swept wings. The method is applicable for model-scale Reynolds numbers all the way through full-scale aircraft in subsonic (not transonic) flight.
LORAAX is designed to analyze wings, of which any number can be modeled in any combination (for example, the traditional stabilizer would be modeled as a second wing). Geometry is defined in a simple XML format. Output files include forces and moments (totals and broken out for each wing), sectional quantities (e.g., lift and drag distributions across the span), and visualizations of the surface and wake. These files are designed to be read in ParaView.
Documentation and validation cases will be added. For now, you can find some initial results and discussion on RCGroups: