AERODYNAMICS & FLIGHT STABILITY OF BLENDED-WING-BODY AIRCRAFT: IN-GROUND- EFFECTS

Abstract

Ground effect is a significant phenomenon that requires evaluation during the design phase of any flight, particularly during take-off and landing. To ensure a successful flight, careful consideration of this phenomenon is critical. Experimental testing is typically done later in the design process due to complexity, time, and cost factors; however, Computational Fluid Dynamics (CFD) is an alternative technique that provides good accuracy in less time. This research aims to study the aerodynamics and dynamic stability of the Blended Wing Body (BWB) aircraft in close proximity to the ground. For this purpose, the SACCON UCAV model is selected, and its static aerodynamics and dynamic stability data have been validated to develop an accurate computational framework. The numerical study is performed at five different non-dimensionalized heights (h/b) near the ground, starting from value 0.2 to 1.0 for static aerodynamics. Three different non-dimensionalized heights (h/b) are simulated for dynamic stability, starting from 0.8 to 1.0. Geometry has been created using CAD software and validated with experimental data for steady and dynamic stability data. The grid has been generated in ICEM with tri-tetra unstructured elements, and two different models (SA & SST-kw) have been used for the validation study. The results of the research demonstrate that observable effects are present in the flight mechanics and steady aerodynamics when non-dimensionalized height (h/b) ≤ 0.2 and the angle of attack (α) ≥ 15o

. This phenomenon in aerodynamic and stability coefficients occurs due to the high-pressure region beneath the Small BWB (SACCON UCAV) in close proximity to the ground. However, at low angle of attacks, the variation in flight mechanics and aerodynamic characteristics is less than 1%. While ground effect has a small impact on the pitch and roll dynamic stability of SACCON UCAV, the pitch and roll dynamic damping coefficient does not vary considerably with changes in height (h/b). Furthermore, no significant change in flow characteristics of SACCON UCAV has been observed in pitch and roll dynamic simulations. The variation in aerodynamic and dynamic stability coefficients is less than 5% for small BWB (SACCON UCAV).