Numerical Investigation of the NASA High-Lift Airfoil with a Conformal Vortex Generator at Transonic Speed

Abstract

Numerical investigation of airflow at a transonic speed over the wing of the NASA high-lift Common Research Model (CRM) with and without a conformal vortex generator (CVG), placed on the airfoil suction side has been performed. The objective of the investigation was to assess the impact of CVG on the wing?s lift to drag (L/D) ratio and tip vortices. The wing has aspect and taper ratios of respectively 9, and 0.275, and a leading-edge sweep angle of 37.24 degrees. The root and tip chords were respectively 11.81m and 2.73 m with an approximate mean chord of 6.62 m. The CVG was distorted V-shaped with a base distance of approximately 4.8 cm, depth of 8.8 cm, and a tip-to root angle of approximately 30.2?. The CVG is on both sides of the tape pointing in opposite directions. The tape is 2 mm thick, 83 cm wide, spanning the entire length of the wing surface. The leading edge of the CVG tape starts at 60% of the chord from the leading edge of the airfoil. The airspeed was 251 m/sec.at 40,000 ft elevation which corresponds to a Reynolds number based on the mean chord of approximately 3.5x107. Properties of the air at this elevation were used for the simulation. The Mach number was 0.85. These values correspond to a typical cruise speed of commercial airlines. The grid size for the baseline airfoil was approximately 3 million and the one with CVG was about 10 million. Reynolds-Averaged Navier Stokes (RANS) equations along with K-? SST turbulence model with all y+ wall treatment were used. Results have shown a nearly 6% improvement in L/D ratio and reduced tip vortices with CVG in place.