Design Optimization of a Ducted Fan Blended Wing Body UAV using CFD Analysis

Abstract

This project work begins with an overview of various Blended Wing Body aircraft designs in relation to their aerodynamic behaviour. After a preliminary analysis of the ideal aerodynamic performance for the baseline configuration, flow analysis is done to investigate the aerodynamic performance of the baseline design. The emerging BWB aircrafts are mainly designed for a higher speed using Jet engines. This BWB concept is implemented in designing of UAVs for a lower Mach number, with a higher Lift to drag ratio. The UAV design considered in this work belongs to 1 kg class. Existing baseline model geometry is designed using CATIA V5 and analyzed using Computational Fluid Dynamics (CFD) packages. This model is then optimized using conventional optimizing technique for better performances. The Mach number range is kept constant and the whole design is optimized for getting the maximum L/D ratio. The optimization includes changing the parameters such as sweep angle, taper-ratio, wing twist, root and tip chord etc. Studies have carried out for models with and without winglets, and are analyzed. The optimized model is then converted to a ducted fan configuration, for the VTOL characteristics. It is meshed in ICEM-CFD and analyzed in ANSYS CFX, with the inner domain containing the fan rotating, and the outer domain stationary. The loss of plan form area caused due to installation of ducted fan is compensated in optimized design. The cruise flying condition was analyzed at 15 m/s wind speed. The optimized design has a three degree twist at the tip chord. The model produced a normal force over the wing (lift) which satisfies the design cruise condition. The results are validated with the existing literatures.