Abstract
This work shows preliminary results of transonic aerodynamic analyses of a high aspect ratio wing-body model with curved planform. The NASA Common Research Model, representative of a modern transport aircraft, is selected as reference geometry (Chapter 1). Different geometries are designed by shifting back the swept wing airfoils of the CRM between kink and tip stations, thus maintaining the same geometric characteristics, apart from the planform shape. (Ch. 2). A structured hexa_mesh is modeled in ANSYS ICEM CFD by a top-down blocking strategy. An automated procedure is developed to guarantee grid association to any curved wing shape in a wide range of configurations. By changing few variables, the mesh topology is quickly and accurately controlled through CAD implementation of proper features. Additionally, a full parametric script, enables manipulation of nodes density distribution in each region of the fluid domain. This process allows to save human resources and times needed for in series mesh generation; at the same time it ensures very similar grids for different geometries, granting similar discretization errors in CFD analyses (Ch. 3). CRM experimental data of National Transonic Facility is exploited for validation of the CFD analysis, performed in ANSYS FLUENT (Ch. 4). After the simulation of three distinct planforms at varying angles of attack and Reynolds numbers, the best geometry is selected by analyzing numerical results.
The chosen curved planform wing-body model is compared to the original CRM with swept wing (Ch. 5). Analyses are performed for varying angles of attack α and Mach numbers M=0.8, 0.85, 0.875, 0.9. Only for M= 0.875 and 0.9, the curved configuration shows improvements in lift to drag ratio L/D respect to the swept wing: for fixed lift coefficient CL=0.5 the drag reduction is effectively beyond the Mach of Drag Divergence.
The wave drag reduction leads to a higher MDD. As the curved wing produces less lift at equal α, the fuselage drag component negatively affects the comparison at fixed CL. After the wing contribution is isolated, the curved wing shows comparable aerodynamic efficiencies in a 0.3% range at M=0.8 and 0.85 for CL=0.5, but slightly higher (1%) maximum L/D at smaller CL values. Significantly better behavior is shown for M=0.875 and 0.9, confirming the MDD increase.
