Planform Design Research Articles

Research on stability for blended-wing-body aircraft

The primary goal of this research is to research the stability properties of a blended-wing-body (BWB) aircraft. This section examines the assessment and selection of aircraft design parameters, planform design, and reflex wing and conducts a complete aircraft stability analysis. A BWB aircraft conceptual design has been completed and the design. To attain static stability, it was examined and refined. The BWB aircraft's study was performed at three distinct values. The analytical findings were used to calculate the angle-of-attack (AOA) and the stall AOA. We determined the estimated initial departure angle of attack and departure region by assessing the results of the trials and a set of stability criteria.

Design, manufacturing and flight-testing of a fixed-wing, small-scale UAV for the transportation of blood bags to remote locations

The current work presents the design, manufacturing, and flight-testing of a fixed-wing, small-scale Unmanned Aerial Vehicle (UAV). The research activities presented in this paper have all been conducted by the Aristotle Space & Aeronautics Team (ASAT), a Greek aerospace student team, for their participation in the international student competition Air Cargo Challenge 2022. Its mission is to carry bags of blood to a remote location. The design requirements refer to a short take-off distance of 60m of rough terrain, climb time of 60s and a cruise/loiter time of 120s. Size restrictions also apply, as the aircraft must fit inside a 1.5m x 1.5m x 0.5m volume, in its deployed form. A step-by-step presentation of the design procedure is conducted, emphasizing on the critical design decisions, such as the airfoil, cargo bay location and wing planform design. The corresponding trade studies are shown, along with the main advantages of the resulting configuration. The in-house manufacturing process is consequently described, focusing on the molds tooling, as well as on the carbon fiber and fiberglass manufacturing techniques. Finally, the results of the flight testing are shown, including the initial challenges that lead to the fine-tuning of the UAV. The test results are validated against the design data and the overall performance of the aerial vehicle is discussed.

A comparison of wind turbine blade parametrization schemes for planform design optimization

This work compares nodal, spline and interpolation parametrization schemes for wind turbine blade planform design. The comparison is done on a power coefficient maximization problem, where the aerodynamic properties of the blade are computed using the Blade Element Method. The problem is solved using a gradient-based interior-point method with analytic gradients. We show the variation in planform design for each parametrization scheme when the degrees of freedom of the parametrization varies. We compare how the power coefficient converges with increasing degrees of freedom for each scheme. Our results shows that the B´ezier spline, the Piecewise Cubic Hermite Interpolation Polynomial (PCHIP) and Lagrange interpolation schemes present the best grid convergence out of all studied schemes.

Blade planform design optimization to enhance turbine wake control

AbstractThis study considers optimizing the planform of wind turbine blades to ultimately enhance wind plant controls, namely, wake steering strategies. Adjoint‐enabled unsteady actuator line simulations are carried out to obtain gradients for optimization of several different performance objectives with respect to blade chord length at 10 locations along blade span. We demonstrate different blade design optimizations that can maximize time‐averaged lateral wake deflection, entrainment of kinetic energy, or total power of multiple turbines. Our optimized designs can produce a 4+% increase in wake deflection, a 4× increase in vertical kinetic energy entrainment, or a 3.6% increase in power when compared with the baseline case. While lateral wake deflection is only modestly sensitive to chord changes, we find that increasing the outboard chord length can dramatically increase kinetic energy entrainment, resulting in faster wake recovery and gains in net power. While this work develops only a few case studies emphasizing relative performance improvements and general trends, these results show the promise of a framework that combines mid‐fidelity computation with adjoint‐based optimization for control and design problems.

A Study in Aerodynamic Optimization of UAV Helicopter Rotor- Blades Planform in Vertical Motion

According to the objectivity of UAV helicopter, endurance is a valuable performance. To increase the endurance, we need to decrease the helicopter required power. Within the research scope in vertical movement only, 5 parameters of blades planform design were considered as design variables. They are root chord of the blades, taper location, taper ratio, pitch angle, and tip twist angle. Optimization was done using own developed genetic algorithm codes with built-in blade element momentum theory (BEMT) as a performance calculator. It was chosen due to its ability to estimate rotor performance quickly. Several CFD simulation were done to reduce the error of blade element momentum theory calculation. Using constant adjustment methods, BEMT can predict thrust and power with a difference with respect to CFD of 3.8% and 8.2% respectively. The optimization result gives the optimum blades design with improving almost 11% in efficiency which came out from 9.4% reduction in power required which is good for helicopter performance.

Optimal flapping wing shape and kinematics are different for different flight velocities: an analysis on local relative wind

Different species of insects and birds fly differently. Their wing forms and wing motion are different. Understanding the purpose of this difference will lead to successful development of flapping wing vehicles for different purposes. This paper discusses the influence of one of the important factors which affects the aerodynamic performance of a flapping wing: the local instantaneous relative wind. Its distribution along the span of a flapping wing has been analyzed for the practical flight range of advance ratios ranging from 0 to 1.5 and stroke plane orientations ranging from 0 to 90°. In this domain, the variation of spanwise distributions of magnitude and direction of relative wind are presented separately for downstroke and upstroke of a flapping cycle. Accordingly, qualitative suggestions are given for wing planform design, orientation and twist of the wing, and actuation of wing for effective utilization of the relative wind and obtaining the necessary force distributions for different flight phases. The formulation presented will be helpful for experimenting flapping wings in hovering and forward flight; especially for setting the wing twist for a required angle of attack distribution and designing the flapping kinematics in upstroke and downstroke.

Redesign of an upwind rotor for a downwind configuration: design changes and cost evaluation

Abstract. Within this work, an existing model of a Suzlon S111 2.1 MW turbine is used to estimate potential cost savings when the conventional upwind rotor concept is changed into a downwind rotor concept. A design framework is used to get realistic design updates for the upwind configuration, as well as two design updates for the downwind configuration, including a pure material cost out of the rotor blades and a new planform design. A full design load basis according to the standard has been used to evaluate the impact of the redesigns on the loads. A detailed cost model with load scaling is used to estimate the impact of the design changes on the turbine costs and the cost of energy. It is shown that generally lower blade mass of up to 5 % less than the upwind redesign can be achieved with the downwind configurations. Compared to an upwind baseline, the upwind redesign shows an estimated cost of energy reduction of 2.3 %, and the downwind designs achieve a maximum reduction of 1.3 %.

Aeroelastic scaling of flying demonstrator: flutter matching

The traditional approach for the design of aeroelastically scaled models assumes that either there exists flow similarity between the full-size aircraft and the model, or that flow non-similarities have a negligible effect. However, when trying to reproduce the behavior of an airliner that flies at transonic conditions using a scaled model that flies at nearly-incompressible flow conditions, this assumption is no longer valid and both flutter speed and static aerodynamic loading are subject to large discrepancies. To address this issue, we present an optimization-based approach for wing planform design that matches the scaled flutter speeds and modes of the reference aircraft when the Mach number cannot be matched. This is achieved by minimizing the squared error between the full-size and scaled aerodynamic models. This method is validated using the Common Research Model wing at the reference aircraft Mach number. The error in flutter speed is computed using the same wing at model conditions, which are in the nearly-incompressible regime. Starting from the baseline wing, its planform is optimized to match the reference response despite different conditions, achieving a reduction of the error in the predicted flutter speed from 7.79% to 2.13%.

Geometry Design of Coaxial Rigid Rotor in High-Speed Forward Flight

The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions.

Aeroelastic Wing Planform Design Optimization of a Flutter UAV Demonstrator

In this work, a study to design a highly flexible flutter demonstrator for the development and testing of active flutter suppression is presented. Based on the UAV mission, a bi-objective design optimization problem can be formulated. The aeroelastic UAV characteristic and imposed constraints, defined by operational aspects and the structural integrity are described by surrogate modeling. Within the framework of the multi-criteria optimization, an approach to construct the equally spaced Pareto frontier with a new approach for non-convex problems is presented. An efficient Pareto configuration to meet a natural low speed and low frequency is identified and its main influencing design features are analyzed.

Geometric Effects of Shallow Dimples in Turbulent Channel Flows at $$Re_{\tau }\approx 180$$: A Vorticity Transport Perspective

Shallow dimples have shown a great potential to reduce turbulent drag in several experiments. However, the mechanism underlying their effects on turbulence dynamics remains a subject of deliberation. In this numerical study, a vorticity transport perspective is adopted to elucidate the geometric effects of shallow dimples on the turbulence dynamics in a fully-developed turbulent channel flow. The geometric modifications considered in the present direct numerical simulation at a bulk Reynolds number of 2800 include changing the planform design and modulating the streamwise wall slope. The planform design had a significant impact on the mean flow topology and the drag property. Out of the five planform designs, diamond (shape) dimples produced the highest amount of total drag reduction of $$\approx 7\%$$, whereas symmetric circular dimples caused the greatest increase in total drag by $$\approx 6\%$$. Results revealed that geometric modifications of shallow dimples mainly affect the vorticity redistribution process that predominates in the inner region of a turbulent boundary layer, and in turn the generation of Reynolds stress. The drag property of a dimpled surface was found to scale with the velocity–vorticity correlation term representing the physical process of vorticity stretching and reorientation. The occurrence of flow separation near the leading edge of the dimple altered the vorticity dispersion process in the outer region, thereby modifying the generation of Reynolds stress in the bulk flow. On the other hand, the vortex dispersion process in the inner layer can be altered by modulating the streamwise wall slope. Accordingly, the vorticity redistribution process was modified but the near-wall generation of Reynolds stress was unaffected. Thus, only the form drag varied with the streamwise wall slope, while the viscous drag remained largely the same.

Shape optimization of underwater wings with a new multi-fidelity bi-level strategy

This paper proposes a new multi-fidelity bi-level optimization (MFBLO) strategy for shape designs of underwater wings. Firstly, hydrodynamic analyses of the wing planform and sections are decoupled for constructing a bi-level shape optimization frame, which includes an upper-level task merely concerning the wing planform design and several lower-level tasks only related to the section designs. By doing this, the shape design optimization gets remarkable benefits from the reduction of dimension and computational costs. Secondly, the bridge function method combined with three multi-fidelity data fusion approaches CC1, CC2, and CC3 are proposed to conduct the bi-level optimization, respectively. After comparison analyses, CC2 shows higher computational efficiency and accuracy, which is more appropriate for the bi-level shape optimization frame. Finally, compared with the single-level optimization with the fixed planform or sections and the conventional high-dimensional optimization, the proposed MFBLO needs less computation budget and gets higher lift-drag ratio, showing its outstanding advantages in handling the shape optimization of underwater wings.

Influence of Transonic Flutter on the Conceptual Design of Next-Generation Transport Aircraft

Transonic aeroelasticity is an important consideration in the conceptual design of next-generation aircraft configurations. This paper develops a low-order physics-based flutter model for swept high-aspect-ratio wings. The approach builds upon a previously developed flutter model that uses the flowfield’s lowest moments of vorticity and volume-source density perturbations as its states. The contribution of this paper is a new formulation of the model for swept high-aspect-ratio wings. The aerodynamic model is calibrated using offline two-dimensional unsteady transonic computational-fluid-dynamics simulations. Combining that aerodynamic model with a beam model results in a low-dimensional overall aeroelastic system. The low computational cost of the model permits its incorporation in a conceptual design tool for next-generation transport aircraft. The model’s capabilities are demonstrated by finding transonic flutter boundaries for different clamped-wing configurations and investigating the influence of transonic flutter on the planform design of next-generation transport aircraft.

Drag power kite with very high lift coefficient

Abstract As an alternative to conventional wind turbines, this study considered kites with onboard wind turbines driven by a high airspeed due to crosswind flight (“drag power”). The hypothesis of this study was, that if the kite's lift coefficient is maximized, then the power, energy yield, allowed costs and profit margin are also maximized. This hypothesis was confirmed based on a kite power system model extended from Loyd's model. The performance of small-scale and utility-scale kites in monoplane and biplane configurations were examined for increasing lift coefficients. Moreover, several parameters of the utility-scale system were optimized with a genetic algorithm. With an optimal lift coefficient of 4.5, the biplane outperformed the monoplane. A 40 m wing span kite was expected to achieve a rated power of about 4.1 MW with a power density of about 52 kW/m2. A parameter sensitivity analysis of the optimized design was performed. Moreover, to demonstrate the feasibility of very high lift coefficients and the validity of a utilized simplified airfoil polar model, CFDs of a proposed high-lift multi-element airfoil were performed and the airfoil polars were recorded. Finally, a planform design of a biplane kite was proposed.

Aeroelastic Model for Macrofiber Composite Actuators on Micro Air Vehicles

The main focus of this research is the generation of a computational aeroelastic model for a macrofiber composite actuated micro air vehicle. Two M8528-P1 actuators were used to deform the surface of a forward-swept thin, compliant composite wing. The general approach, which included MATLAB, ABAQUS, and Athena Vortex Lattice, is described. The planform design and initial flight testing are discussed. The computational model was validated first with static tests, and then quasi-static wind-tunnel tests were used to validate the aeroelastic model. Digital image correlation was used to compare the expected and measured displacements of the wing. Flight loads were also compared for various angles of attack. The results indicated good agreement for angles of attack well within the standard flight envelope, despite small discrepancies in geometry.

Aerodynamic and Stability Analysis of Blended Wing Body Aircraft

The main purpose of the paper is to study the aerodynamic and stability characteristics of a blended-wing-body (BWB) aircraft. This paper presents the estimation and selection of aircraft design parameters, planform design, reflex airfoils, and conduct thorough stability investigation of the aircraft. A conceptual design of BWB aircraft has been done and the design was analyzed and refined to achieve static stability. The CFD analysis of the BWB aircraft was done at three different values of angle-of-attack (AOA) and thus the stall AOA was determined from the computational results. The dynamic stability of the aircraft has been studied under five modes namely- short period, phugoid, Dutch-roll, roll and spiral. The static stability has been achieved with a wide positive value of static margin. Results also show that the aircraft is dynamically stable for longitudinal and lateral modes when subjected to disturbances in respective conditions. The BWB aircraft fulfils the criteria of Class I Category B aircraft and shows flight level 1 characteristics in all stability modes.

Optimal FWMAV Wing Design for a Combination of Energy-Effective Hovering and Roll Control

Energy-effective hovering and active flight control are of paramount importance for the usefulness of Flapping Wing Micro Air Vehicles (FWMAVs). Recent studies have focused on separate parts (e.g., wing planform design, wing kinematics, or flight control) rather than on the complete system. This work presents a combined approach to find an optimal wing design (i.e., wing planform and pitching kinematics) for energy-effective hovering and roll control. Relatively simple mathematical descriptions are used for the kinematics, the aerodynamics and the roll motion to allow its use in optimization techniques. Results show that the wing design depends significantly on the relative importance of either energy-effective hovering or effective roll control during the optimization. The roll control effectiveness increases if the wing area around the wingtip is increased to push the center of lift outwards. Additionally, we show that the most effective control variable, to enforce the required body moment for the roll motion, depends strongly on the wing design. In conclusion, flapping wing design requires, in general, a combined approach to guarantee both energy-effective hovering and effective roll control.

다단 최적 설계 프레임워크를 활용한 전기추진 항공기 프로펠러 공력 최적 설계

본 연구에서는 프로펠러나 헬리콥터 로터와 같은 회전체의 공력 최적 설계를 위한 다단 최적 설계 프레임워크를 제안한다. 이 프레임워크는 플랜폼 설계와 단면의 형상 설계를 반복적으로 수행하는 설계 전략을 통해 회전체의 공력 성능 향상을 목표로 한다. 플랜폼 설계의 단계에서는 유전 알고리즘과 2차원 CFD 데이터베이스 기반의 깃 요소 모멘텀 이론을 이용하여 빠른 시간에 회전체의 공력 특성을 평가하여 최적점을 탐색하였다. 플랜폼 설계 후 단면에 유입되는 유동 조건을 예측하여 단면 형상 최적 설계를 수행하였다. 설계 과정에서 보다 면밀하게 유동 특성이 분석될 수 있도록 2차원 N-S 해석자와 민감도 기반의 최적화 알고리즘을 통해 최적해를 탐색하였다. 단면 형상이 설계된 후에는 최적의 유동 조건을 산출할 수 있도록 플랜폼 설계를 반복적으로 수행하였다. 본 프레임워크를 1kW급 전기추진용 항공기 프로펠러 설계에 적용하여 그 유효성을 3차원 N-S 해석과 풍동 실험을 통해 검증하였다. 설계 후, 풍동 실험 결과를 기준으로 약 5%의 프로펠러 효율 증가를 얻을 수 있었다. A multi-level design optimization framework for aerodynamic design of rotary wing such as propeller and helicopter rotor blades is presented in this study. Strategy of the proposed framework is to enhance aerodynamic performance by sequentially applying the planform and sectional design optimization. In the first level of a planform design, we used a genetic algorithm and blade element momentum theory (BEMT) based on two-dimensional aerodynamic database to find optimal planform variables. After an initial planform design, local flow conditions of blade sections are analyzed using high-fidelity CFD methods. During the next level, a sectional design optimization is conducted using two dimensional Navier-Stokes analysis and a gradient based optimization algorithm. When optimal airfoil shape is determined at the several spanwise locations, a planform design is performed again. Through this iterative design process, not only an optimal flow condition but also an optimal shape of an EAV propeller blade is obtained. To validate the optimized propeller-blade design, it is tested in wind-tunnel facility with different flow conditions. An efficiency, which is slightly less than the expected improvement of 7% predicted by our proposed design framework but is still satisfactory to enhance the aerodynamic performance of EAV system.

Challenge of design exploration for small blended wing body using unstructured flow solver

In this study, the conceptual design and the aerodynamic shape optimization of a 150 PAX class blended wing body type aircraft, which was named as Novel-Wing-Body (NWB), is discussed. The modified geometry parameterization is developed based on authors’ previous study for the planform design. The airfoil is defined to obtain better aerodynamic performance based on NASA-SC(2)0711. In addition, double-tapered wing is employed for outboard wing to arrow of higher sweepback angle without increasing the structured weight. The aerodynamic design exploration is carried out with this modified geometry representation. According to the design exploration result, it is found that the most solutions show better performance than that of the best solution obtained by previous study, and it is also suggests that the promising designs has large sweep back and, the sharp fuselage-nose.

Parametric Representation and Shape Optimization of Flapping Micro Air Vehicle Wings

The effects of wing planform on the aerodynamic performance of a rigid wing in forward flapping flight and hovering configurations were investigated in this paper. The planform design space was parameterized using a new, modified Zimmerman method based on low aspect ratio Zimmerman planform designs. The aerodynamic forces on the wing were calculated using Peters' aerodynamics with an assumed inflow coupled with blade element theory. A multiobjective optimization approach was taken to find the best planform designs for three objectives: wing area, peak power input, and an aerodynamic force based on the kinematic configuration – lift for hovering and thrust for forward flight. A gradient-based optimizer and the ε-constraint method were used to find the Pareto front of optimal designs with the aerodynamic force as the primary objective function. The choice of primary and secondary objective functions is important in determining the optimal planform. The Pareto optimal planforms for the case when only area is considered as a secondary objective function drastically differ from the optimal planforms when only power is taken as a secondary objective function. As the secondary objective ε values change over the design space, so do the optimal planform shapes.