Lift Distribution Research Articles

Aerodynamic Analysis of Unnamed Aerial Vehicle Serindit V-2 Using Computational Fluid Dynamics

Serindit V-2 is an unnamed aircraft by the Serindit Aero UAV research team. It has the ability to fly rapidly in order to compete in KRTI in the Racing Plane division. Although it has been successfully produced and able to fly, comprehensive research on aerodynamic of Serindit V-2 aircraft flying behavior has never been done before. Aerodynamic research needs to be conducted to improve the aircraft performance such as flying capability, air resistance efficiency and etc. This study aims to determine the value of flow characteristic such as coefficient of drag, lift, moment and pressure distribution based on fluid flow that occurs in the aircraft with variations of Angle of Attack and air velocity. The method used is CFD (Computational Fluid Dynamic) which is a computer-based numerical method and performed with an iterative procedure to predict aerodynamic characteristics and fluid flow phenomena on the aircraft surface. Simulations were carried out using Ansys Fluent 2017 software on the Serindit V-2 aircraft model sourced from the Serindit Aero Team. The result of the lift coefficient value is CLo=0.3666 and CLMax value = 1.42626 at α 13o. The CDo obtained was 0.0589258. While the CMo value obtained is -8.34 x 10-5.

Multipoint Aerodynamic Shape Optimization of a Truss-Braced-Wing Aircraft

The truss-braced-wing (TBW) aircraft is a promising innovative design for the next-generation airliner. Nevertheless, for a full TBW wing–body–tail configuration, it is still a challenge to perform the comprehensive refined aerodynamic design. Especially, the complex mutual interference among the wing, struts, and fuselage should be analyzed in detail. Meanwhile, for its one-design cruise condition with and , the aerodynamic explorations and performances of drag divergence and near-buffet-onset condition are also fateful. To address these issues, we utilize high-fidelity Reynolds-averaged Navier–Stokes solver and gradient-based optimizer to conduct aerodynamic optimization designs, including a single-point optimization, a two-point optimization, and a three-point optimization. Results indicate that the single-point design obtains a nearly shock-free configuration with an approximate elliptical lift distribution and an of 24.09. Also, the refined local aerodynamic analyses lead to a good understanding of the complicated interactions with several junctions. For multipoint optimizations, both optimized configurations have the same level aerodynamic behavior on cruise condition compared with the single-point result, and they have a satisfying performance of drag divergence. Moreover, the three-point optimization design shows excellent aerodynamic efficiency with some extra off-design points evaluations, whereas the two-point optimization still has an undesirable off-design result.

Multi-Fidelity Approach to Predicting Multi-Rotor Aerodynamic Interactions

Recent years have seen a growing interest in large electric multirotor aircraft for urban air mobility, commercial package delivery, cargo, and military applications. This has led to efforts that aim to model the interactional aerodynamics of rotors operating in close proximity and its impact on performance. While computational fluid dynamics can accurately characterize the physics of multirotor interaction, in most cases it is too computationally demanding for performing studies over a range of parameters. On the other hand, lower-fidelity models approximate the underlying physics and are computationally inexpensive, but are often imprecise in predicting the fields of interest. In this study, we present a multifidelity approach that inherits the accuracy of a high-fidelity method, while retaining the computational efficiency of a low-fidelity model. With this approach, the low-fidelity model is used to span the entire space of parameters and identify key parameter values to perform high-fidelity simulations. A few selected high-fidelity simulations performed at these parameter values are then used in a lifting procedure to determine multifidelity solutions at other parameter values. In this paper we apply this strategy to determine the lift and drag distributions of a two-rotor assembly as a function of the longitudinal and vertical distance between them. We conclude that this strategy can substantially improve upon the low-fidelity results.

Influence of lift distribution coefficient on hydrodynamic performance of propeller in forward and astern mode of operation by numerical analysis

Influence of lift distribution coefficient on hydrodynamic performance of propeller in forward and astern mode of operation by numerical analysis

Numerical investigation of the impact of tubercles and wing fences on the aerodynamic behaviour of a fixed-wing, tactical Blended-Wing-Body UAV platform

In this work, a study on the impact of passive flow control techniques on an Unmanned Aerial Vehicle (UAV) Blended Wing Body (BWB) is presented. The novel BWB layout integrates smoothly the wing to the fuselage, creating an aerodynamically superior platform. However, the lack of vertical stabilizers in the form of a tail, creates the need for aerodynamically stable and efficient wings that can withstand the spanwise flow. To that end, two passive flow control techniques are implemented in this study, namely the wing fences and the tubercles. Wing fences are vanes or airfoils attached vertically to the lifting surface and are one of the oldest flow control techniques used in aerospace applications to stop the spanwise flow. Wing fences extending from the leading edge to the trailing edge completely stop the spanwise flow. On the other hand, tubercles are sinusoidal modifications of the blade’s leading edge. This is a novel flow control technique, with the original concept inspired from the characteristic flipper of the humpback whale (Megaptera Novaeangliae). Each bump creates a set of counter-rotating vortices that acts as a virtual fence and stops the spanwise flow. The results from this comparison show that flow control techniques can offer a considerable benefit to the flying capabilities of a BWB UAV platform, by improving the lift distribution and increasing the maximum coefficient of lift.

Conceptual design of sonic boom stealth supersonic transports

This paper introduces a supersonic transport aircraft design model developed in the GENUS aircraft conceptual design environment. A conceptual design model appropriate to supersonic transports with low-to-medium-fidelity methods are developed in GENUS. With this model, the authors reveal the relationship between the sonic boom signature and the lift and volume distributions and the possibility to optimise the lift distribution and volume distribution together so that they can cancel each other at some region. A new inspiring design concept—sonic boom stealth is proposed by the authors. The sonic boom stealth concept is expected to inspire the supersonic aircraft designers to design low-boom concepts through aircraft shaping and to achieve low ground impacts. A family of different classes of supersonic aircraft, including a single-seat supersonic demonstrator (0.47 psf), a 10-passenger supersonic business jet (0.90 psf) and a 50-seat supersonic airliner (1.02 psf), are designed to demonstrate the sonic boom stealth design principles. Although, there are challenges to balance the volume with packaging and control requirements, these concepts prove the feasibility of low-boom low-drag design for supersonic transports from a multidisciplinary perspective.

Design and analysis of a tail sitter (VTOL) UAV composite wing

In recent years the design and development of various classes of unmanned aerial vehicles (UAV's) has grown significantly. It is a well-known fact that the utilization of composite structures will reduce the weight of the aircraft structure by 30–50%. It is possible to tailor the strength and stiffness properties of composite structures by adopting different material or lamination configurations. In this work redesign of the Tail Sitter (Vertical Take Off and Landing/VTOL) UAV wing is carried out in order to improve the performance by reduction of the weight. Numerical investigation is carried out to reduce the weight of the wing by replacing the existing Aluminum frame with different ply configurations of CFRP and GFRP and also by reducing number of spars. The strength and stiffness of the UAV wing was analysed by Finite Element Method. Baseline analysis was carried out on the Aluminium structure by applying the span wise lift distribution along the wing based on Dr Ing Oster Schrenk’s Approximation method. For the VTOL UAV configuration the wing has to carry the motor, so structurally wing should have higher stiffness-to weight ratio to carry the high loads. The present work was focussed on analysis of different ply configurations of CFRP as well as GFRP using FE methods in order to get better performance in terms of weight reduction. The analysis was done by configuring the whole wing frame along with spars and ribs, which gave high stiffness to the wing compared to the Conventional wing. From the CFD analysis, it is evident that composite wing had less deformation compared to the aluminium wing and the wing structure was redesigned using CFRP and GFRP based composites. Effect of lay-up configuration on the performance is also studied for composite wing. Due to high stiffness to weight ratio of composite wing it is found there is a reduction in weight of the wing by 44.17% compare to aluminium. A redesign of the wing is done by having a composite frame of two spars and five Ribs.

Aerodynamic Design and Strength Analysis of the Wing for the Purpose of Assessing the Influence of the Bell-Shaped Lift Distribution

This article deals with aerodynamic and structural calculations of several wing designs to compare the influence of the shape on the lift distribution. Various shapes of wings for the required lift and bending moment were optimized to minimize drag and thereby reduce fuel consumption. One example was a wing with a bell-shaped lift distribution, which was proposed by Ludwig Prandtl and has been forgotten over the years. The first part of the paper focuses on minimization of the wing drag coefficient by a low fidelity method and the results are compared with the CFD calculation with good agreement. In the structural part of the analysis, the inner layout of the studied wings was designed. The structural design, containing elementary wing components and optimization loop, was carried out to minimize weight with respect to panel buckling. From these calculations the weights of wings were obtained and compared. In the last part of this study, an analysis of flight performance of an airplane with presented wings was performed for a selected flight mission. Results indicated that, for the free optimized wing, the fuel saving was about six percent.

A Study on Aerodynamics and Stability Characteristics of a Bell-Shaped Span-Load Wing

The existence of the new bell-shaped span-load wing is said to has the best lift distribution especially comparing to the elliptical wing. Bell-shaped span-load wing is designed by configuring the twist of the wing. However, the information on the aerodynamic and stability characteristics of the bell-shaped span-load wing is limited. Thus, the main purpose of the research is to evaluate the aerodynamic and stability characteristic to strengthen the claim of the capability of bell-shaped span-load wing in producing minimum induced drag. As the research is expected to be beneficial to the aviation design team, detailed information regarding the lift distribution as well as the induced drag produced is analysed at the optimum angle of attack and the results is further explained in this research. The numerical method for the analysis is done by using Lifting Line Theory (LLT) in the XFLR5 software which can analyse the wings of aircraft in terms of its aerodynamic and stability characteristic. Then, the comparison of the aerodynamic characteristics for bell-shaped span-load, elliptical span-load and tapered wing done in this research is to strengthen the appeal made stating that the bell-shaped span-load wing is the best type of wing ever existed and may replace the elliptical wing as the best wing shape with aerodynamically most efficient. The research has proven that along the wingspan, the bell-shaped span-load wing produced the lowest and minimum induced drag when being compared. At the optimum angle of attack of bell-shaped span-load wing, though the lift produced is slightly lower than the elliptical and tapered wing, the difference in the induced drag is obvious as bell-shaped span-load wing produces induced drag that is lower than 0. In other words, starting from the semi span of the wing to the wingtip, the bell-shaped span-load wing managed to be the most aerodynamically efficient wing.

Structural Design and Analysis of a Light Aircraft Wing

The aim of this study is to perform structural design and analysis of a light aircraft wing. Both aerodynamic analysis and structural design of the wing are covered. The aerodynamic analysis is achieved by using Schrenks Approximation Method simulated in MATLAB to estimate the lift distribution. In addition, static stress analysis of the wing is carried out to compute the stresses at wing structure when subjected to the generated aerodynamic loads and thereby examine its structural reliability. The stresses are estimated by using the finite element software package MSC/NASTRAN/PATRAN. A maximum Von Mises stress of 135MPa is obtained which is less than the yield stress for aluminum alloy used in wing design. On the other hand, and based on the finite element model, a free-vibration analysis is performed for the whole model. The frequencies for the first three modes and the corresponding mode shapes are presented. The purpose of this study is to correlate and validate the finite element model against the modal test in preparation for further complex analysis. The finite element results have shown that the suggested wing configuration of the light aircraft is safe, with margins of safety equal to 1.33 which occurs at the root section.

Experimental Validation and Evaluation of a Coupled Twist-Camber Morphing Wing Concept

A morphing wing concept allowing for coupled twist-camber shape adaptation is proposed. The design is based on an optimized thickness distribution both spanwise and chordwise to be able to morph the wing sections into targeted airfoil shapes. Simultaneously, the spanwise twist is affected by the actuation. The concept provides a higher degree of control on the lift distribution which can be used for roll control, drag minimization, and active load alleviation. Static deformation and flight tests have been performed to evaluate and quantify the performance of the proposed mechanism. The ground tests include mapped actuated wing shapes, and wing mass and actuation power requirements. Roll authority, load alleviation, and aerodynamic efficiency estimates for different configurations were calculated using a lifting line theory coupled with viscous 2D airfoil data. Roll authority was estimated to be low when compared to a general aviation aircraft while the load alleviation capability was found to be high. Differences between the lift to drag ratio between the reference and morphing wing configurations are considerable. Mass and actuation energy present challenges that can be mitigated. The flight tests were used to qualitatively assess the roll control capability of the prototype, which was found to be adequate.

AN ALTERNATIVE APPROACH TO INDUCED DRAG REDUCTION

Induced drag constitutes approximately 40% of the total drag of subsonic civil transport aircraft at cruise conditions. Various types of winglets and several non-planar concepts, such as the C-wing, the joined wings, and the box plane, have been proposed for its reduction. Here, a new approach to induced drag reduction in the form of a combination of an elliptical and an astroid hypocycloid lift distribution is put forward. Lift is mainly generated from high circulation in the center part of the wing and fades away along the semi-span towards the wing tip. Using lifting line theory, the analysis shows that for fixed lift and wingspan the combined lift distribution results in an induced drag reduction of 50% with respect to the elliptical distribution. Due to its wing planform the combined lift distribution leads to a 51.5% higher aspect ratio. If structural constraints are placed, then the higher aspect ratio may affect wing weight. Although any substantial increase of wing weight is not envisaged, further study of the matter is required. Zero-lift drag and lift-dependent drag due to skin friction and viscosity-related pressure remain unaffected. The proposed lift distribution is particularly useful in a blended wing-body design.

Effects of wing twist on lift and drag characteristics of blended wing body aircraft

Blended Wing Body is a revolutionary concept offering phenomenal performance advantages over conventional aircraft. There are various aerodynamic features that are added to the wing in order to adjust the lift distribution and wing twist is one of them. This paper presents a progressive study to examine the effects of twist angles on the aerodynamic characteristics of a Blended Wing Body (BWB) aircraft. CFD analysis is carried out on seven BWB models having wing twists ranging from +3° to -3°. Each model is analyzed at four different Mach numbers. The coefficient of drag (Cd) and coefficient of lift (Cl) is determined and plotted against the twist angle to obtain a trend. The Cl/Cd ratio is also calculated to observe the overall aerodynamic performance of the BWB.

Lift on a magnetized airfoil in a weakly resistive inviscid plasma

AbstractAn airfoil in the form of a plate is immersed into an inviscid conducting fluid with parallel flow and magnetic field. The insertion of a magnetic field in the plate yields a perturbation that may be dealt with by using asymptotic expansions in powers of the magnetic diffusivity. The first terms yield a formula expressing the lift on the airfoil as an Abel transform of the magnetic field in the plate. Inversion of the Abel transform provides appropriate fields for any desired lift distribution along the plate.

Low-Order Modeling of Wingtip Vortices in a Vortex Lattice Method

Wingtip-flow effects on the aerodynamic forces and moments of a wing become increasingly significant as the aspect ratio decreases. These effects are dominated by the tip vortex and an associated suction zone, which results in a supplementary “vortex lift” that is not captured by conventional vortex lattice methods (VLMs). Although many augmented VLMs have addressed such free-vortical flows on the leading edges of delta wings and even wingtips, they do not account for the portion of the vorticity that may be supported by the attached flow at the tip. The current work consists of an augmented VLM designed to capture the geometry and strength of the free tip vortex along the wingtip, and it is distinguished from prior models by the capability to allocate vorticity between the bound wingtip flow and the free tip-vortex flow at each chordwise position. This paper presents the model and its predictions of tip-vortex positions, as well as forces and moments on low-aspect-ratio wings. The model demonstrates lift distributions typical of vortex lift, promising agreement with forces and moments from experimental work as well as modulation of the forces and moments by selection of the maximum allowable bound vorticity along the tips.

Comparison of Theoretical and Multifidelity Optimum Aerostructural Solutions for Wing Design

As contemporary aerostructural research for aircraft design trends toward high-fidelity computational methods, aerostructural solutions based on theory are often neglected or forgotten. In fact, in many modern aerostructural wing optimization studies, the elliptic lift distribution is used as a reference in place of theoretical aerostructural solutions with more appropriate constraints. In this paper, the authors review several theoretical aerostructural solutions that could be used as reference cases for wing design studies, and these are compared to high-fidelity solutions with similar constraints. Solutions are presented for studies with 1) constraints related to the wing integrated bending moment, 2) constraints related to the wing root bending moment, and 3) structural constraints combined with operational constraints related to either wing stall or wing loading. It is shown that, under appropriate design constraints, theoretical solutions for the optimum lift distribution may capture aerostructural coupling sufficiently to serve as appropriate reference cases for higher-fidelity solvers. A comparison of theoretical and high-fidelity solutions for the optimum wingspan and corresponding drag reveals important insights into the effects of certain aerodynamic and structural parameters and constraints on the aerodynamic and structural coupling involved in aerostructural wing design and optimization.

A morphing wing with cellular structure of non-uniform density

This paper proposes an optimization design method for the modular cellular structure of non-uniform density, which is filled into the morphing wing to generate variable torsion angle. By actively adjusting the distribution of the span-wise torsion angle, the lift distribution on the wing surface can be properly adjusted to avoid the problem of aeroelastic divergence or reduce the bending moment at the wing root. This ability is validated using CFD simulation. In the optimization framework proposed, the adaptive gradient algorithm is used to suppress the divergence of iteration. A finite element model with geometrical nonlinear effects is then proposed to correct the errors of the linear analysis and verify the effectiveness of the optimization method. This design is shown to be able to reduce the overall weight of the structure and achieve control of the macro mechanical performance of the wing. The work provides a general optimization design method for similar modular structures, allowing independent programmable adjustment of the parameters of each single structural cell.

Evolutionary and Hereditary Traits of an Albatross and its Aerodynamic Optimality

The aerodynamic efficiency of the albatross has always fascinated researchers and the designing of drones mimicking the albatross’s aerodynamic traits have been a major area of interest for the aerospace industry. This review sheds light on the traits behind an albatross’s aerodynamic efficiency such as dynamic soaring, bell shaped lift distribution and provides insights into its hereditary posed encodings and evolutions. The soaring techniques have been introduced and discussed along with the albatross’s morphology and structure which is responsible for its efficiency. In addition, the albatross’s navigational and foraging strategies are briefly discussed to provide a better understanding of the effects of atmospheric conditions on the albatross’s flight characteristics and the limitations.

Sectional analysis of revolving wings: Effect of leading-edge and trailing-edge vortices

The role of leading-edge vortex (LEV) in lift generation for revolving wings is not well-understood. We aim to discern the effect of LEVs and TEVs on revolving flat and twisted wings through a detailed analysis of planar flow in the wing sections. We present a simple quasi-two-dimensional model to estimate the lift distribution over the wingspan by coupling the potential flow and lifting line theory (modified to incorporate the effect of wing rotation) and incorporating the presence of vortices. This semi-analytical model estimates a fairly accurate sectional force trend for low-moderate AoA at each wing section and subsequently the net lift force developed on the wing. Three-dimensional numerical simulations verify the developed theory. The present results underscore the role of LEVs and TEVs in the mechanism of lift generation. Furthermore, the proposed theoretical model serves as a non-intrusive method to estimate the lift distribution over the wingspan from a three-dimensional velocity field.

Seamless Active Morphing Wing Simultaneous Gust and Maneuver Load Alleviation

This paper deals with the simultaneous gust and maneuver load alleviation problem of a seamless active morphing wing. The incremental nonlinear dynamic inversion with quadratic programming control allocation and virtual shape functions (denoted as INDI-QP-V) is proposed to fulfill this goal. The designed control allocator provides an optimal solution while satisfying actuator position constraints, rate constraints, and relative position constraints. Virtual shape functions ensure the smoothness of the morphing wing at every moment. In the presence of model uncertainties, external disturbances, and control allocation errors, the closed-loop stability is guaranteed in the Lyapunov sense. Wind tunnel tests demonstrate that INDI-QP-V can make the seamless wing morph actively to resist “1-cos” gusts and modify the spanwise lift distribution at the same time. The wing root shear force and bending moment have been alleviated by more than 44% despite unexpected actuator fault and nonlinear backlash. Moreover, during the experiment, all the input constraints were satisfied, the wing shape was smooth all the time, and the control law was executed in real time. Furthermore, as compared with the linear quadratic Gaussian control, the hardware implementation of INDI-QP-V is easier; the robust performance of INDI-QP-V is also superior.