Vortical Flow Prediction of the AVT-183 Diamond Wing

Abstract

The objective of this paper is to assess the potential and limitations of current practice in computational fluid dynamic modeling for predicting vortical flowfields over a generic 53degree swept diamond wing with rounded leading edges. This wing was designed under STO AVT Task Group 183 and is based on the SACCON UCAV geometry, which is a lambda wing with complex span-wise distributions of thickness and leading edge radius and with a linear twist outboard of the first trailing edge break. The SACCON wing trailing-edge was swept forward by 26.5-degrees to form a diamond-shaped planform that is used in this study. This new wing also has a constant NACA 64A-006 airfoil section with a leading edge radius of 0.264 percent chord and has no twist. CFD simulations were performed for various angles of attack at a Mach number of 0.15 and a Reynolds number of 2.7× 10 based on the mean aerodynamic chord to match experiments. CFD simulations were run with different turbulence models and with a limited assessment of Delayed Detached Eddy Simulation. The wind tunnel experiments of the diamond wing were carried out in the Institute of Aerodynamics and Fluid Mechanics of the Technische Universitat Munchen, Germany and include aerodynamic lift, drag, and pitch moment measurements as well as span-wise pressure distributions at different chord-wise locations. This data set is used to validate the CFD results. The results presented demonstrate that the CFD compare well with the experiments at small angles of attack; the pitch moment predicted by the SARC turbulence model provide a better match to experimental results than the SA model at moderate angles of attack; and at high angles of attack, CFD predictions are not as good. The flow visualization results show that a leading-edge vortex is formed above the upper surface of the wing at an angle of attack of about eight degrees. This vortex becomes larger and stronger when the angle of attack is increased. With increasing angle of attack, the vortex formation point moves upstream and the vortex core moves inboard towards the wing center. Finally, the results show that the flow over the diamond wing is steady throughout the range of angles of attack.