Unsteady airload of an airfoil with variable camber

Mesarič, M.; Kosel, Franc

doi:10.1016/j.ast.2003.10.007

Cited by 7 publications

(5 citation statements)

References 10 publications

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“…These aircrafts are discussed in different sections of current review paper. Mesaric and Kosel (2004) investigated the prediction of unsteady airloads imposed on a variable-camber wing that change over time with deformation. Several methods were used for the analysis.…”

Section: Camber Motivation For Adoption In Small Aircraftmentioning

confidence: 99%

A Review of Morphing Aircraft

Barbarino

Bilgen

Ajaj

et al. 2011

Journal of Intelligent Material Systems and Structures

1,111

647

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Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions, but the performance at each condition is sub-optimal. The ability of a wing surface to change its geometry during flight has interested researchers and designers over the years as this reduces the design compromises required. Morphing is the short form for metamorphose; however, there is neither an exact definition nor an agreement between the researchers about the type or the extent of the geometrical changes necessary to qualify an aircraft for the title ‘shape morphing.’ Geometrical parameters that can be affected by morphing solutions can be categorized into: planform alteration (span, sweep, and chord), out-of-plane transformation (twist, dihedral/gull, and span-wise bending), and airfoil adjustment (camber and thickness). Changing the wing shape or geometry is not new. Historically, morphing solutions always led to penalties in terms of cost, complexity, or weight, although in certain circumstances, these were overcome by system-level benefits. The current trend for highly efficient and ‘green’ aircraft makes such compromises less acceptable, calling for innovative morphing designs able to provide more benefits and fewer drawbacks. Recent developments in ‘smart’ materials may overcome the limitations and enhance the benefits from existing design solutions. The challenge is to design a structure that is capable of withstanding the prescribed loads, but is also able to change its shape: ideally, there should be no distinction between the structure and the actuation system. The blending of morphing and smart structures in an integrated approach requires multi-disciplinary thinking from the early development, which significantly increases the overall complexity, even at the preliminary design stage. Morphing is a promising enabling technology for the future, next-generation aircraft. However, manufacturers and end users are still too skeptical of the benefits to adopt morphing in the near future. Many developed concepts have a technology readiness level that is still very low. The recent explosive growth of satellite services means that UAVs are the technology of choice for many investigations on wing morphing. This article presents a review of the state-of-the-art on morphing aircraft and focuses on structural, shape-changing morphing concepts for both fixed and rotary wings, with particular reference to active systems. Inflatable solutions have been not considered, and skin issues and challenges are not discussed in detail. Although many interesting concepts have been synthesized, few have progressed to wing tunnel testing, and even fewer have flown. Furthermore, any successful wing morphing system must overcome the weight penalty due to the additional actuation systems.

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Section: Camber Motivation For Adoption In Small Aircraftmentioning

confidence: 99%

A Review of Morphing Aircraft

Barbarino

Bilgen

Ajaj

et al. 2011

Journal of Intelligent Material Systems and Structures

1,111

647

View full text Add to dashboard Cite

show abstract

“…Substituting Eq. (25) into Eq. (15) results in the following two equations for the steady and damping components of the nondimensional basic …”

Section: Quasi-steady Load Distributionmentioning

confidence: 98%

“…This study was restricted to a circular arc parabolic camberline, which was meant to represent chordwise aeroelastic deformations. Mesaric and Kosel [25] determined the lift and pitching moment for cubic polynomial camberlines. No mention was made of the load distribution.…”

Section: Introductionmentioning

confidence: 99%

Unsteady thin airfoil theory revisited for a general deforming airfoil

2010

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The unsteady thin airfoil theory of von Karman and Sears is extended to analyze the aerodynamic characteristics of a deforming airfoil. The von Karman and Sears approach is employed along with Neumark's method for the unsteady load distribution. The wake-effect terms are calculated using either the Wagner or Theodorsen function, depending on the desired camberline deformation. The concept of separating the steady and damping terms in the camberline boundary condition is introduced. The influence of transient and sinusoidal airfoil deformations on the airfoil load distribution is examined. The general equations developed for the unsteady lift and load distribution are evaluated analytically for a morphing airfoil, which is defined here by two quadratic curves with arbitrary coefficients. This general camberline is capable of modeling a wide range of practical camberline shapes, including leading and trailing edge flaps. Results of the present model are shown for a variable camber, or morphing, airfoil configuration. The influence of transient and sinusoidal motion on the force coefficients and load distribution is addressed.

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“…Here, a numerical approach to calculate the aerodynamic pressure on the plate is presented following Theodorsen's theory [34]. Closed-form solutions for the unsteady pressure on curved plates described by a cubic polynomial have been derived by Mesaric and Kosel [37]. According to Theodorsen [34], small oscillations are assumed and the following linearized boundary condition is enforced: @ @ @w @t U @w @ (9) where U is the undisturbed flow velocity.…”

Section: Aerodynamic Modelmentioning

confidence: 99%

Flutter of Partially Rigid Cantilevered Two-Dimensional Plates in Axial Flow

2008

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The introduction of adaptive materials for active camber line shape control favors flexible wing designs, thus making adaptive wings more susceptible to instability phenomena. Motivated by a new wing concept for micro aerial vehicle applications, the aeroelastic stability of partially rigid cantilevered plates in an axial flow is investigated. The plate is modeled as a beam having a rigid and a flexible part. The beam is modeled using the classical Euler-Bernoulli bending theory, the unsteady aerodynamic pressure is modeled using Theodorsen's theory, and the Rayleigh-Ritz method is used to obtain a discrete model. Stability analysis is carried out in Laplace's domain. The results indicate that a partially rigid cantilevered plate in an axial flow does not show static aeroelastic divergence but exhibits dynamic aeroelastic instability. The flutter velocity at which this instability occurs is dependent on the ratio of the flexible length to the total length of the plate and the mass ratio. Adding a rigid part ahead of a flexible plate can have a stabilizing or destabilizing effect on the aeroelastic behavior of the flexible plate, depending on the mass ratio. The phase-angle difference between the upstream and downstream part of the two-dimensional plate is shown to be dependent on the mass ratio and flexible length fraction. Jumps in the flutter diagram occur because of changes in flutter mode, and the flexible length fraction also affects these jump phenomena. The jumps are shown to be the result of eigenvalue branch collision. There are multiple critical flow conditions for mass ratios around the jumps. Therefore, a new practical flutter boundary definition is introduced to remove the overlap between flutter modes near the jumps. The flutter diagram calculated according to the new definition shows better agreement with published time domain simulations. Nomenclature A = aerodynamic matrix A i = Fourier coefficient b = half-chord C s = Theodorsen's function D = plate bending stiffness F = force vector f = ratio of the flexible plate length to the total plate length G = decay factor H n = Hankel function of the nth kind K = stiffness matrix K n = modified Bessel function of the second kind k = reduced frequency L = length of the flexible plate M = bending moment M = mass matrix m = structural mass n = number of modes p = pressure q = dynamic pressure q = degree-of-freedom vector s = Laplace variable s = nondimensional Laplace variable T = kinetic energy U = undisturbed flow velocitỹ U = nondimensional airspeed U = potential energy v = generalized momentum vector w = out-of-plane displacement = vorticity per unit length = reduced damping = transformed coordinate = air densitỹ = mass ratio of the air mass to the flexible plate mass = damping = velocity potential ' = phase angle = shape function ! = frequency Subscripts a = aerodynamic c = circulatory nc = noncirculatory s = structural Superscriptŝ = Laplace transform _ = first time derivative = second time derivative

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Unsteady airload of an airfoil with variable camber

Cited by 7 publications

References 10 publications

A Review of Morphing Aircraft

A Review of Morphing Aircraft

Unsteady thin airfoil theory revisited for a general deforming airfoil

Flutter of Partially Rigid Cantilevered Two-Dimensional Plates in Axial Flow

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