Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame

Jones, William T.; Nielsen, Eric J.; Lee-Rausch, Elizabeth M.; Acree, C. W.

doi:10.2514/6.2014-0290

Cited by 10 publications

(14 citation statements)

References 25 publications

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“…Regarding the multi-point optimisation, 10 design cycles were required. This is in agreement with data publish in the literature [1].…”

Section: Discussionsupporting

confidence: 94%

“…Note that the torque coefficient C Q is normalised by the baseline rotor torque coefficient C Q , so that the cost function I is O (1). The quantity C T denotes the thrust coefficient of the baseline rotor.…”

Section: Objective and Constraint Functionsmentioning

confidence: 99%

“…Its value represents the sweep atr = 1, and a parabolic sweep distribution is imposed in the range [0. 8,1]. The value of the design variable α 9 is limited to [−0.5c, 0.15c], where a positive number denotes a shift of the blade section in the direction pointing from trailing to leading edge.…”

Section: Parametrisation Techniquementioning

confidence: 99%

“…They showed that a compromise solution can be selected from the Pareto front, which has 3.2% higher FoM in hover and 6.5% higher η in aeroplane mode with respect to the XV-15 baseline blade. Multi-point optimisation based on a gradient method was carried out by Jones et al [1] for the Tilt-Rotor Aeroacoustics Model (TRAM) [22]. They employed the unstructured FUN3D flow solver [23,24], coupled with a discrete adjoint solver, to determine the optimal aerofoil shapes, twist and taper.…”

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confidence: 99%

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Tiltrotor CFD Part II - aerodynamic optimisation of tiltrotor blades

et al. 2017

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This paper presents aerodynamic optimisation of tiltrotor blades with high-fidelity computational fluid dynamics. The employed optimisation framework is based on a quasi-Newton method, and the required high-fidelity flow gradients were computed using a discrete adjoint solver. Single-point optimisations were first performed, to highlight the contrasting requirements of the helicopter and aeroplane flight regimes. It is then shown how a trade-off blade design can be obtained using a multi-point optimisation strategy. The parametrisation of the blade shape allowed to modify the twist and chord distributions, and to introduce a swept tip. The work shows how these main blade shape parameters influence the optimal performance of the tiltrotor in helicopter and aeroplane modes, and how a compromise blade shape can increase the overall tiltrotor performance. Moreover, in all the presented cases, the accuracy of the adjoint gradients resulted in a small number of flow evaluations for finding the optimal solution, thus indicating gradient-based optimisation as a viable tool for modern tiltrotor design. overall profile drag coefficientbaseline rotor torque coefficient Greek Symbols INTRODUCTIONThe aerodynamic design of tiltrotor blades is a challenging task, requiring the best compromise in performance between hover and propeller modes [1,2]. In hovering flight, the blade aerodynamics is characterised by strong interaction with the rotor wake, resulting in a significant effect of the induced drag on the total drag [3]. The propeller mode, on the other hand, is dominated by strong compressibility effects, especially at high advance ratio, resulting in a prominent contribution of the profile and wave drag components [4]. As a consequence, to accurately capture the effect of the blade shape on the optimal rotor design, the use of high-fidelity flow models is required. Unlike in the case of helicopter and propeller blades, the aerodynamic optimisation of tiltrotor blades has not been the subject of considerable research. The present work analyses the contribution of the main blade shape parameters to the optimal performance of the tiltrotor using high-fidelity computational fluid dynamics (CFD). It also demonstrates the use of gradient-based optimisation and the discrete adjoint for the efficient design of tiltrotor blades. Aerodynamic optimisation needs large computational resources, since each design point requires the solution of a set of partial differential equations. The choice of the optimisation algorithm is therefore crucial. Broadly speaking, the optimisation algorithms can be classified in gradient-based or gradient-free methods. Gradient-based methods usually require a limited number of flow evaluations [5], and this makes them particularly attractive for complex aerodynamic optimisation problems. They need, however, the computation of flow derivatives with respect to the design variables, which can be a very expensive task, unless the adjoint method is used. Also, gradient-based methods are local in nat...

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“…Regarding the multi-point optimisation, 10 design cycles were required. This is in agreement with data publish in the literature [1].…”

Section: Discussionsupporting

confidence: 94%

Section: Objective and Constraint Functionsmentioning

confidence: 99%

Section: Parametrisation Techniquementioning

confidence: 99%

mentioning

confidence: 99%

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Tiltrotor CFD Part II - aerodynamic optimisation of tiltrotor blades

et al. 2017

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“…NASA also demonstrated adjoint-based design capability for turbulent flow over a UH60 helicopter in forward flight. 7 High-fidelity design is happening, right now.…”

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confidence: 97%

Towards high-fidelity aerospace design in the age of extreme scale supercomputing (Invited)

Wang

2015

22nd AIAA Computational Fluid Dynamics Conference

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Comprehensive Optimization of the Unmanned Tilt-Wing Cargo Aircraft With Distributed Propulsors

Chen

Jia

et al. 2020

IEEE Access

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The unmanned tilt-wing cargo aircraft using distributed propulsors is an emerging aircraft significantly different from traditional types. This paper proposes an aerodynamic, propulsion, noise, weight integrated optimization design method for this new aircraft. The method consists of several functional modules specially developed or adjusted targeting the aircraft's characteristics, such as the boundary state analysis, propeller/rotor oblique inflow analysis, waked wing analysis, propeller/rotor noise evaluation, multi-state wing mass analysis, multi-objective genetic algorithm optimization. It comprehensively considers the impact of various complex factors on the optimization results, such as the impact of distributed propulsors on the wing aerodynamics, the effect of wingtip propellers on the induced drag reduction, the coupling between wing aerodynamics and structure, the propeller/rotor aerodynamics optimization, and noise control. With the proposed method, it is possible to directly translate the top-level design requirements into the design scheme with the optimal specific system performance (such as the lowest delivery cost and highest delivery efficiency) at the very initial aircraft design stage, thereby greatly shortening the development cycle. A case study was presented. The results show that the introduction of distributed propulsors can increase the delivery efficiency by 28.2% and reduce the delivery cost by 15%; suppressing the wingtip vortices using propellers can increase the wing lift-drag ratio by 5.43%-6.65%; the slipstream generation efficiency and thrust efficiency are significantly different between different distributed propulsor schemes. To maximize the overall efficiency, it is necessary to balance between the slipstream generation efficiency and the overall thrust efficiency when optimizing the tilt-wing cargo aircraft. INDEX TERMS Convertiplane; Cargo aircraft; Unmanned aerial vehicle; Vertical takeoff and landing; Aircraft multidisciplinary optimization.

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Multi-point Adjoint-Based Design of Tilt-Rotors in a Noninertial Reference Frame

Cited by 10 publications

References 25 publications

Tiltrotor CFD Part II - aerodynamic optimisation of tiltrotor blades

Tiltrotor CFD Part II - aerodynamic optimisation of tiltrotor blades

Towards high-fidelity aerospace design in the age of extreme scale supercomputing (Invited)

Comprehensive Optimization of the Unmanned Tilt-Wing Cargo Aircraft With Distributed Propulsors

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