Effect of Spanwise Discontinuities on the Aerodynamics of a Swept Wing with Scalloped Ice Accretion

Understanding the aerodynamic impact of swept-wing ice accretions is a crucial component of modern aircraft design. Ice-accretion simulation tools are commonly utilized in the design process, but the necessary geometric fidelity of the ice shapes generated by those codes is not fully understood. Assessment of the iced-wing aerodynamics and associated flowfields can provide some guidance regarding the impact of different geometric-fidelity ice-shape representations. Previous tests were performed in the NASA Icing Research Tunnel to acquire high-fidelity ice shapes. From this database, full-span artificial ice shapes were designed and manufactured for a subscale wind-tunnel model based on the Common Research Model. This work investigates the flowfield associated one type of low-fidelity representation of a swept wing with scalloped ice accretion. In an attempt to quantify the aerodynamic impact of the highly three-dimensional features in the high-fidelity ice shape, discontinuities were introduced into a smoothed version of the high fidelity ice shape. Both the spacing between the discontinuities and the angle of cutting plane used for creating the discontinuities were investigated. Comparisons are made between the wing with these 3D discontinuous ice shapes as compared to the high-fidelity case by examining surface oil flow visualization and surface pressure data in addition to the standard aerodynamic performance parameters. At angles of attack less than approximately 6 deg., the flowfield on the wing appears similar between the 3D discontinuous configurations and the high fidelity case. Streamwise streak features dominate the surface flow. As the angle of attack increases, these flow features remain the dominant feature for the high fidelity configuration relative to any of the 3D discontinuous ones. The flowfield on the wing with the high fidelity ice shape transitions to a flow dominated by a spanwise leading-edge vortex as the angle of attack increases further. Some of the 3D discontinuous configurations do result in a similar flowfield at approximately 10 deg. angle of attack, but others never resulted in a similar flowfield. A close inspection of the flowfields shows that none of the 3D discontinuous configurations results in a flowfield consistently similar to the high fidelity configuration across a range of angles of attack. The complex flowfield associated with a swept wing with a highly three dimensional scalloped ice accretion cannot be reproduced simply by replacing that ice shape with a smooth ice shape made artificially discontinuous.