Structural optimization of an underwater glider with blended wing body

Introduction

Underwater glider is a new type of autonomous underwater vehicle (AUV) which changes movement state by adjusting buoyancy and converts the lift on wings into propulsive force. Compared to the traditional propeller propulsion underwater vehicle, gliders have excellent hydrodynamic performance and cruising capacity which satisfy long-range and extended-duration deployments. The configuration of conventional underwater gliders is based on revolving body with fins and rudders, which have the characteristics of large volume and high compressive capacity, such as the Spray^[1] and Seaglider.^[2]

For achieving higher hydrodynamic efficiency, blended-wing-body (BWB) configuration was used to the design of underwater gliders. This configuration has no clear dividing line between the wings and the main body of the craft, which provides higher maximum lift-to-drag ratio and lower wetted area to volume ratio. Jenkins et al.^[3] have fully studied the feasibility of BWB underwater gliders. Office of Naval Research (ONR)^[4] developed a BWB design model, "Liberdade XRay," which is the world's largest known underwater glider. The ZRay underwater glider was a modified form of the XRay underwater glider which completed in March 2010, having capacity of 1600 lb dry weight, 20-ft wing span, 1200-1500-km cruise range, maximum lift-to-drag ratio of 20, and operational depth of 300 m.^[5] Sun et al.^[6] designed a parametric geometric model of an underwater glider with BWB, and the shape optimization was carried out.

Structural optimization of aircraft with BWB configurations have been studied by many institutes.^[7]-[9] The first BWB designs proposed by Liebeck^[10] used traditional skin and stringer arrangements. Mukhopadhyay^[11] presented an efficient structural model development and design process of a mega transport BWB concept. Hansen et al.^[12] proposed the structural analysis of BWB aircraft configurations using a physics-based mass prediction method. Cho et al.^[13] presented the preliminary structural design and analysis of an ultra-heavy-lifting BWB military cargo transport. Gern^[14] proposed a fast and flexible finite element model (FEM) for structural analysis, optimization, and weight calculation for BWB designs; Laughlin et al.^[15] developed a physics-based multidisciplinary analysis and weight optimization environment for structural weight estimation of the BWB aircraft.

There may be no sufficient resources to analyze all of the combinations of variables that one would wish because finite element analysis (FEA)...