Abstract
In this paper, a Double-stage Surrogate-based Shape Optimization (DSSO) strategy for Blended-Wing-Body Underwater Gliders (BWBUGs) is proposed to reduce the computational cost. In this strategy, a double-stage surrogate model is developed to replace the high-dimensional objective in shape optimization. Specifically, several First-stage Surrogate Models (FSMs) are built for the sectional airfoils, and the second-stage surrogate model is constructed with respect to the outputs of FSMs. Besides, a Multi-start Space Reduction surrogate-based global optimization method is applied to search for the optimum. In order to validate the efficiency of the proposed method, DSSO is first compared with an ordinary One-stage Surrogate-based Optimization strategy by using the same optimization method. Then, the other three popular surrogate-based optimization methods and three heuristic algorithms are utilized to make comparisons. Results indicate that the lift-to-drag ratio of the BWBUG is improved by 9.35% with DSSO, which outperforms the comparison methods. Besides, DSSO reduces more than 50% of the time that other methods used when obtaining the same level of results. Furthermore, some considerations of the proposed strategy are further discussed and some characteristics of DSSO are identified.
Highlights
Underwater glider (UG) is a new kind of AutonomousUnderwater Vehicle (AUV) which was first presented by Stommel (1989)
We mainly focus on optimizing a specific steady cruising process with a constant angle of attack and velocity, without considering the buoyancy control system and gravity longitudinal position control system
7 Conclusions In this paper, a novel shape optimization strategy is proposed based on the characteristics of the Blended-Wing-Body Underwater Gliders (BWBUGs) shapes
Summary
Underwater Vehicle (AUV) which was first presented by Stommel (1989). Traditional AUVs always appear in a torpedo shape with a power propulsion system (Alam et al, 2014), while the UGs glide through the water by controlling their buoyancy and converting the lift on wings into propulsive force (Bachmayer et al, 2004). A novel Double-stage Surrogatebased Shape Optimization (DSSO) strategy is proposed based on the characteristics of the BWBUG shape to reduce the computational cost. (1) A DSSO strategy is newly proposed to reduce the computational cost for shape design optimization of BWBUG. Where X represents the design variables of the problem, BL and BU are the lower and upper boundaries of the design space, TA0, TB0 and TC0 denote the MRTs of the three baseline airfoils and are set as 0.22, 0.16 and 0.10, respectively. The primary purpose of this work is to propose a new shape optimization strategy for BWBUGs, which can reduce the computational cost. (8) By regarding the LDRs of the three sectional airfoils as the inputs, the SSM for the BWBUG is constructed with calculated samples, which is denoted as y. Validated to have better performance than some other SBO methods in dealing with computational-expensive problems
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