Multi-objective optimization of a wing fence on an unmanned aerial vehicle using surrogate-derived gradients

Abstract

In this paper the multi-objective, multi-fidelity optimization of a wing fence on an unmanned aerial vehicle (UAV) near stall is presented. The UAV under consideration is characterized by a blended wing body (BWB), which increases its efficiency, and a tailless design, which leads to a swept wing to ensure longitudinal static stability. The consequence is a possible appearance of a nose-up moment, loss of lift initiating at the tips and reduced controllability during landing, commonly referred to as tip-stall. A possible solution to counter this phenomenon is wing fences: planes placed on top of the wing aligned with the flow and developed from the idea of stopping the transverse component of the boundary layer flow. These are optimized to obtain the design that would fence off the appearance of a pitch-up moment at high angles of attack, without a significant loss of lift and controllability. This brings forth a constrained multi-objective optimization problem. The evaluations are performed through Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations. However, since controllability cannot be directly assessed through Computational Fluid Dynamics (CFD), surrogate-derived gra-

A Brief Review on Aerodynamic Performance of Wingtip Slots and Research Prospect

“…Some variant designs of winglets have appeared over the next years. The (B) tip fence is an endplate at the wingtip to reduce the occurrence of tip vortex and induced drag [64,65]. It is easy to install on the wing without any modification to the shape of the wing itself.…”

Surrogate-Assisted Parametric Study of a Wing Fences for Unmanned Aerial Vehicles

“…The surrogates that are used to perform this study are the result of the constrained multi-objective optimization of stall speed and controllability subjected to pitching moment equilibrium ( , ℎ (x) = 0) and longitudinal static stability ( , ℎ (x)/ < 0) [38]. The speed (and thus angle of attack and the elevon deflection ) can be determined from the lift, drag and moment coefficient by solving the equilibrium equations.…”

“…The first objective of this paper is the working principles of a wing fence when applied to a BWB UAV and unify the existing theories. This is achieved by comparing the initial design (ID) with a design optimized for stall speed and controllability while maintaining stability, called the overall better design (OBD) (see Table 3) [38]. The design parameter settings, stall speed and controllability coefficient of the ID and OBD are presented in Table 3.…”

“….87, = 0.54}, part of the DoE of Wauters et al [38] using the 2 -criterion * ). This observation is conform the observation by Rudenko & Ryzhkova [11] but contrary to the observations by Haines, Fozard * The 2 -criterion [44] measures the excess of rotation rate over the strain rate magnitude by considering the second eigenvalue of the symmetric tensor 2 + Ω 2 ; where and Ω are the symmetric and antisymmetric components of the ∇ defined as = 1 2 ( ∇ + ( ∇ ) ) and Ω = 1 2 ( ∇ − ( ∇ ) ).…”

Design optimization-under-uncertainty of a forward swept wing unmanned aerial vehicle using SAMURAI

“…Even though a number of solutions were introduced to tackle the problem of tip stalling, only a handful can be used on the blended wing body aerial vehicle after its manufacturing (typically addressed as aerodynamic afterthoughts). 33 An alternative approach is a conceptual redesign (typically addressed as an aerodynamic aforethought) of the aircraft to make it inherently free of the occurrence of tip-stall. This can for example be obtained by means of sweeping the wings forward.…”