Rectangular Wing Research Articles

Wings shape effect on behavior of hybrid nanofluid inside a channel having vortex generator

Thermal and flow characteristics of hybrid nanofluid inside a channel having vortex-generator with different wing shapes, is investigated numerically. Three different wing shapes, including rectangular, triangular, and trapezoidal, are considered. The geometrical configuration considered in this work is representative of a channel with three wings in each row; one mounted to the top plate and the other ones mounted to the bottom plate and this trend changes between the plates alternately. MgO-MWCNT (50:50) suspended in the ethylene glycol (EG) as base fluid with volume fractions of 0.1%, 0.2%, 0.4%, and 0.6% is considered as working fluid. The effects of volume fraction of the nanoparticles and type of wings in the Reynolds number range of 200–1600, are investigated. Heat transfer coefficient, pressure drop and performance evaluation criterion (PEC) are the most important parameters that investigated at different flow conditions. The results shown that rectangular wings leads to increase the heat transfer coefficient. In addition the channel with trapezoidal and triangular wings at the same volume fraction, have the higher values of PEC due to lower pressure drop. Also the result indicated that heat transfer coefficient are enhanced by increasing the nanoparticles volume fraction. According to obtained results, the trapezoidal wings with nanofluid volume of fraction of 0.6 and minimum Reynolds number leads to desirable performance from heat transfer and fluid flow viewpoint.

A Study of Model Separation Flow Behavior at High Angles of Attack Aerodynamics

This paper analyzes the aerodynamic performance and flow separation characteristics of a rectangular wing for varying Reynolds numbers. The mechanism of separation and its effect on the rectangular wing were simulated in ANSYS FLUENT using K-ω SST turbulence model. A detailed analysis was performed to discuss aspects like the lift and drag force of the wing surface, surface pressure distribution around the wing surface, flow separation characteristics for different angles of attack, velocity profiles at different sections of the wing surface along the chord length, and the effect of wing tip vortices. The simulation results showed that by increasing the angles of attack, the separation point moves towards the leading edge and the onset of stalling is very much closer to the leading edge. Also, the experimental and numerical results indicated that NACA4415 airfoil had enhanced coefficient of lift to coefficient of drag ratio at the angles of attack (AoA) ranging between 4◦ and6◦,which are distinctively advantageous for the better performance of small-scale wind turbine rotors. The experimental and computational results were analyzed in the context of effective change in stalling characteristics at different Reynolds numbers.

Numerical Investigation on Effect of Multiple Winglets for Wind Turbine Applications

The present article is an effort to examine the potential of multiple winglets to reduce the induced drag of the aerodynamic surface. The advantages of using multiple winglets include reduction of induced drag, increased L/D and improved performance of the Wind turbine. Computational Fluid Dynamics is utilized as to approach the effects of multiple winglets with NACA 24012 airfoil section for untwisted, rectangular wing. The testing of configurations is done at Reynolds number 290,000. FLUENT solver incorporated in ANSYS used for the numerical investigation of the steady flow over the wing. A substantial improvement in lift curve slope occurs with dihedral spread of the winglets. The dihedral spread also distributes the tip vortices.

Numerical and experimental assessment of random matrix theory to quantify uncertainty in aerospace structures

Abstract The increased complexities of modernized structures have catalyzed additional research over the past few decades to accurately quantify the variabilities within static designs, which can be categorized into parametric, non-parametric and experimental uncertainties. The majority of works have dealt with parametric uncertainty alone and utilize algorithms that require priori knowledge of the input uncertainty. This is problematic since there is a large number of uncertain variables that typically percolate physical engineering problems which are difficult to characterize using precise probability distributions. A unified method to encompass these stochastic properties in a computationally efficient manner is needed and one such approach is using random matrix theory (RMT), which has integrated and validated its importance through various fields, however largely excluding the aerospace sector. This study utilizes RMT and the Wishart distribution to characterize modal uncertainties that arise due to parametric, non-parametric and experimental variabilities. Numerical studies are undertaken with finite element models of a rectangular wing and an aircraft wing box to validate RMT and the Marchenko-Pastur (MP) density function. An experimental study is also conducted on six nominally designed aircraft T-tails, where RMT is used to provide a quantitative bound on the unknown uncertainties that exist within the physical system.

Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings

A method is presented to model the incompressible, attached, unsteady lift and pitching moment acting on a thin three-dimensional wing in the time domain. The model is based on the combination of Wagner theory and lifting line theory through the unsteady Kutta–Joukowski theorem. The results are a set of closed-form linear ordinary differential equations that can be solved analytically or using a Runge–Kutta–Fehlberg algorithm. The method is validated against numerical predictions from an unsteady vortex lattice method for rectangular and tapered wings undergoing step or oscillatory changes in plunge or pitch. Further validation is demonstrated on an aeroelastic test case of a rigid rectangular finite wing with pitch and plunge degrees of freedom.

Experimental investigation of propeller slipstream effects on the wing aerodynamics and boundary layer treatment at low Reynolds number

In this research, an experimental investigation was conducted to predict the Laminar-turbulent transition over the wing surface. Furthermore, the effects of a tractor propeller slipstream on both wing aerodynamics and transition front were studied. For tests, a rectangular wing was used with a NACA 6-series airfoil section and with a total of 22 pressure orifices. Unsteady pressure measurements were performed over the upper and lower surfaces of the wing in different spanwise locations at different incidence angles. Existence of propeller slipstream changed pressure distribution over the wing surfaces, in both chordwise and spanwise directions and hence affected the wing loading distribution. Statistical analysis of pressure signals was used to predict the boundary layer transition over the wing by computing the root mean square and skewness of the pressure data. The results showed that the transition location moves toward the leading edge due to propeller slipstream. Increase in propeller rotational speed causes that the turbulent flow covers whole portion of the wing surface.

The method of relocation of boundary condition for the problem of electromagnetic wave scattering by perfectly conducting thin objects

A three-dimensional problem of monochromatic electromagnetic wave scattering by perfectly conducting body of small thickness is considered. The numerical method for the solution of this problem, based on the relocation of the boundary condition to the median surface is developed. In this method we state a new boundary value problem in the domain outside this surface. The original shape of the body is taken into account due to the boundary conditions. Further, the resulting problem reduces to a system of two integro-differential equations on the median surface. A numerical scheme for solving these equations is developed. This scheme does not degenerate when the body thickness tends to zero. The developed method has been tested by the example of the problem of electromagnetic wave scattering by the body in the form of a rectangular wing.

A Hybrid Reduced-Order Model for the Aeroelastic Analysis of Flexible Subsonic Wings—A Parametric Assessment

A hybrid reduced-order model for the aeroelastic analysis of flexible subsonic wings with arbitrary planform is presented within a generalised quasi-analytical formulation, where a slender beam is considered as the linear structural dynamics model. A modified strip theory is proposed for modelling the unsteady aerodynamics of the wing in incompressible flow, where thin aerofoil theory is corrected by a higher-fidelity model in order to account for three-dimensional effects on both distribution and deficiency of the sectional air load. Given a unit angle of attack, approximate expressions for the lift decay and build-up are then adopted within a linear framework, where the two effects are separately calculated and later combined. Finally, a modal approach is employed to write the generalised equations of motion in state-space form. Numerical results were obtained and critically discussed for the aeroelastic stability analysis of a uniform rectangular wing, with respect to the relevant aerodynamic and structural parameters. The proposed hybrid model provides sound theoretical insights and is well suited as an efficient parametric reduced-order aeroelastic tool for the preliminary multidisciplinary design and optimisation of flexible wings in the subsonic regime.

Aerodynamics of porous airfoils and wings

This paper presents novel wind tunnel test results on the aerodynamics of a symmetric thin porous airfoil and a porous rectangular half wing using a symmetric thin airfoil as its cross section, obtained by a six-component force balance. The variation of lift coefficient, drag coefficient, pitching moment, lift versus drag, the gradient of lift, and location of the aerodynamic center with respect to the angle of attack are presented as a function of the porosity. The data, where possible, are compared with the analytical results. The trend of the experimental results behaves in the same manner as the analytical solution. The measured drag coefficients of the airfoil and wing are also presented. The applicability of the standard equation relating the lift coefficient of a non-porous wing with that of a non-porous airfoil to the case of porous wings is verified by applying the equation to porous wings and validating the results using experimental data. Lift slope decreases as the porosity increases. The drag decreases at a low value of porosity and then increases as porosity increases. The standard equation for obtaining the lift coefficient of a wing from the lift coefficient of an airfoil is applicable and valid for porous wings and airfoils.

Analytical structural behaviour of elastic flapping wings under the actuator effect

ABSTRACTThe effect of inertial forces on the Structural Dynamics (SD) behaviour of Elastic Flapping Wings (EFWs) is investigated. In this regard, an analytical modal-based SD solution of EFW undergoing a prescribed rigid body motion is initially derived. The formulated initial-value problem is solved analytically to study the EFW structural responses, and sensitivity with respect to EFWs’ key parameters. As a case study, a rectangular wing undergoing a prescribed sinusoidal motion is simulated. The analytical solution is derived for the first time and helps towards a conceptual understanding of the overall EFW's SD behaviour and its analysis required in their designs. Specifically, the EFW transient and steady response in on-off servo condition is also attended.

Experiments of Propeller-Induced Flow Effects on a Low-Reynolds-Number Wing

Novel findings are discussed in this paper that will be especially beneficial to designers and modelers of small-scale unmanned air vehicles and high-altitude long-endurance vehicles that both operate at low Reynolds numbers (). Propeller-induced flow effects in both tractor and pusher configurations on a rectangular wing using the Wortmann FX 63-137 airfoil (a common low-Reynolds-number high-lift airfoil) are presented in this paper. Significant performance benefits can be found for a wing in the tractor configuration. Experiments, including trip tests and upper-surface oil flow visualization, show and verify that the propeller slipstream induces early transition to turbulent flow in the regions within the slipstream and the premature formation of a separation bubble in the regions outside the slipstream. The result is a reduction of pressure drag and an increase in lift of the wing where lift-to-drag ratios are as high as 10–12 (a maximum of 70% increase in lift-to-drag ratio from a clean wing configuration) and are measured at both low and high angles of attack up to stall (0–16 deg). Similar performance benefits are not observed in pusher configuration results where only increased local flow velocity and varying inflow angle effects are apparent. Thus, contrary to the design rules for optimal performance of wings at high Reynolds numbers, at low Reynolds numbers, a propeller in the tractor configuration exhibits significant performance improvements, especially in cruise configurations (low angles of attack), as compared with a propeller in the pusher configuration or even a clean wing.

Structural Optimization of Platelike Aircraft Wings Under Flutter and Divergence Constraints

Minimum-weight aircraft wing design, with an emphasis on avoiding aeroelastic instability, has been studied since the 1960s. The majority of works to date were posed as sizing problems; only a handful of researchers have employed a topology optimization approach. The aim of this study is to use the level set method for this purpose. The problem is formulated as one of plate thickness distribution, which takes on one of two prescribed values at every point on the wing planform. This is combined with constraints implemented on the eigenvalues of the flutter equation; such an approach is shown to be robust and versatile. Optimization results for rectangular plate wings at a range of sweep configurations studied previously are included to validate the present methods. Delta, high-aspect-ratio, and typical swept transport wing planforms are then optimized. All solutions demonstrate the ability to significantly reduce wing mass while maintaining flutter and divergence speed above a specified limit, which can be higher than that of the reference, maximum-thickness design. The proposed method can be used to provide insights into optimal aeroelastic wing structures and is particularly useful for developing unconventional aircraft structural configurations.

A Multi-Fidelity Approach for Aerodynamic Performance Computations of Formation Flight

This paper introduces a multi-fidelity computational framework for the analysis of aerodynamic performance of flight formation. The Vortex Lattice and Reynolds Averaged Navier–Stokes methods form the basis of the framework, as low- and high-fidelity, respectively. Initially, the computational framework is validated for an isolated wing, and then two rectangular NACA23012 wings are considered for assessing the aerodynamic performance of this formation; the optimal relative position is through the multi-fidelity framework based on the total drag reduction. The performance estimates are in good agreement with experimental measurements of the same configuration. Total aerodynamic performance of formation flight is also assessed with respect to attitude variations of the lifting bodies involved. The framework is also employed to determine the optimal position of blended-wing-body unmanned aerial vehicles in tandem formation flight.

Flow interactions of two- and three-dimensional networked bio-inspired control elements in an in-line arrangement

We present experiments that examine the modes of interaction, the collective performance and the role of three-dimensionality in two pitching propulsors in an in-line arrangement. Both two-dimensional foils and three-dimensional rectangular wings of AR = 2 are examined. In contrast to previous work, two interaction modes distinguished as the coherent and branched wake modes are not observed to be directly linked to the propulsive efficiency, although they are linked to peak thrust performance and minimum power consumption as previously described (Boschitsch et al 2014 Phys. Fluids 26 051901). In fact, in closely-spaced propulsors peak propulsive efficiency of the follower occurs near its minimum power and this condition reveals a branched wake mode. Alternatively, for propulsors spaced far apart peak propulsive efficiency of the follower occurs near its peak thrust and this condition reveals a coherent wake mode. By examining the collective performance, it is discovered that there is an optimal spacing between the propulsors to maximize the collective efficiency. For two-dimensional foils the optimal spacing of X* = 0.75 and the synchrony of ϕ = 2π / 3 leads to a collective efficiency and thrust enhancement of 42% and 38%, respectively, as compared to two isolated foils. In comparison, for AR = 2 wings the optimal spacing of X* = 0.25 and the synchrony of ϕ = 7 π / 6 leads to a collective efficiency and thrust enhancement of 25% and 15%, respectively. In addition, at the optimal conditions the collective lateral force coefficients in both the two- and three-dimensional cases are negligible, while operating off these conditions can lead to non-negligible lateral forces. Finally, the peak efficiency of the collective and the follower are shown to have opposite trends with increasing spacing in two- and three-dimensional flows. This is correlated to the breakdown of the impinging vortex on the follower wing in three-dimensions. These results can aid in the design of networked bio-inspired control elements that through integrated sensing can synchronize to three-dimensional flow interactions.

Direct measurement of the Sears function in turbulent flow

The applicability of the strip assumption in the estimation of the unsteady lift response of a two-dimensional wing in turbulent flow is investigated. The ratio between the lift spectrum calculated from the two-wavenumber analysis and the lift spectrum calculated from the strip assumption is used to evaluate the accuracy of the strip assumption. It is shown that the accuracy of the strip assumption is controlled by the ratio of the turbulence integral scale to the chord and the aspect ratio. With an increase of these two parameters, the ratio for evaluating the accuracy of the strip assumption increases, the one-wavenumber transfer function obtained from the strip assumption approaches the Sears function gradually. When these two parameters take suitable values, the strip assumption could be applicable to the calculation of the unsteady lift on a wing in turbulent flow. Here, the term aspect ratio refers to the ratio of the specified span (an finite spanwise length of the two-dimensional wing) to the chord, the unsteady lift is calculated over this specified spanwise length. The theoretical analysis is verified by means of force measurement experiments conducted in a wind tunnel. In the experiment, a square passive grid is installed downstream of the entrance of the test section to generate approximately homogeneous and isotropic turbulence. Three rectangular wings with different aspect ratios ($\unicode[STIX]{x1D703}=3$, 5 and 7) are used. These wing models have an NACA 0015 profile cross-section and a fixed chord length$c=0.16~\text{m}$. The testing results show that, at a fixed ratio of turbulence integral scale to chord, the deviation between the experimental one-wavenumber transfer function obtained from the strip assumption and the Sears function is reduced with increasing aspect ratio, as expected by the theoretical predictions. However, due to the effect of thickness, the experimental values at high frequencies cannot be captured by the Sears function which is derived based on the flat plate assumption. In practical applications, the effect of thickness on the transfer function should be considered.

Heat transfer enhancement of micro-scale backward-facing step channel by using turbulators

Laminar forced convection heat transfer and fluid flow of micro-scale backward-facing step (MBFS) with different types of longitudinal vortex generators (VGs) is numerical analyzed. The governing equations are discretized by finite volume method. Four basic types of VG which are rectangular and triangular wings and winglets pairs are attached to an unheated upper wall behind the stepped wall in order to enhance the thermal performance of MBFS. Three inclination angles of VGs are considered namely; 30°, 45°, and 60° with a wide range of water flow rate. The thermal and hydraulic performance of MBFS with VG is evaluated by JF factor in order not to show the enhancement in the heat transfer only, but the increase in the pressure drop as well. The results showed that the use of VG in MBFS increases the heat transfer and pressure drop simultaneously. The best heat transfer enhancement with a little increase in the pressure drop is observed in the case of rectangular wing VG at an attack angle of 60° and Reynolds number of 180 whereas (NuVG/Nuo) = 1.221. JF factor increases with Reynolds number until 180 and then a steep decrease has been monitored.

Hovering efficiency comparison of rotary and flapping flight for rigid rectangular wings via dimensionless multi-objective optimization

In this work, a multi-objective optimization framework is developed for optimizing low Reynolds number () hovering flight. This framework is then applied to compare the efficiency of rigid revolving and flapping wings with rectangular shape under varying and Rossby number (, or aspect ratio). The proposed framework is capable of generating sets of optimal solutions and Pareto fronts for maximizing the lift coefficient and minimizing the power coefficient in dimensionless space, explicitly revealing the trade-off between lift generation and power consumption. The results indicate that revolving wings are more efficient when the required average lift coefficient is low (<1 for and <1.6 for ), while flapping wings are more efficient in achieving higher . With the dimensionless power loading as the single-objective performance measure to be maximized, rotary flight is more efficient than flapping wings for regardless of the amount of energy storage assumed in the flapping wing actuation mechanism, while flapping flight is more efficient for . It is observed that wings with low perform better when higher is needed, whereas higher cases are more efficient at regions. However, for the selected geometry and , the efficiency is weakly dependent on when the dimensionless power loading is maximized.

The influence of fixed transition modeling on aeroelastic simulations in comparison to wind tunnel experiments

This paper presents the results from three-dimensional fluid–structure interaction simulations of an aeroelastic wind tunnel experiment which was conducted in the Transonic Wind Tunnel in Gottingen, Germany in 2013. The experimental setup consisted of two wings: a rectangular NACA0010 wing, which was used as a gust generator, and further downstream a three-dimensional elastic wing representing the outer part of a typical transport-aircraft wing, the so-called ‘Aerostabil’ wing. Laminar-turbulent boundary layer transition has been tripped to generate turbulent flow. The investigations in this paper are focused on the numerical influence of fixed transition compared to fully turbulent simulations. The effect of the different aerodynamic modeling becomes most obvious for higher angles of attack. Steady aeroelastic simulations including fixed transition modeling show more accurate numerical results than the fully turbulent simulations when compared to experimental data. Moreover, unsteady simulations reveal a significant reduction of unsteady loads for simulations with fixed transition compared to fully turbulent simulations.

Numerical aerodynamic of the rectangular wing concerning to ground effect

Numerical aerodynamic of the rectangular wing is presented regarding to the ground effect. Clark-Y wing section is selected for the present calculations. The Reynolds-averaged Navier-Stokes (RANS) equations solver of the ANSYS-CFX software is employed with a realizable k-e turbulent model. The numerical results lift and drag of the rectangular airfoil at ground effect are verified with the experimental data. Pressure distribution and velocity contour and turbulent intensity at the trailing edge of the airfoil are presented and discussed.

Global Optimization of Wing Aerodynamic Optimization Case Exhibiting Multimodality

An investigation into an aerodynamic optimization benchmark case that exhibits multimodality is presented using a global optimization approach. The recently suggested case 6 of the AIAA Aerodynamic Design Optimization Discussion Group involves the drag minimization of a rectangular NACA0012 wing subject to lift and the root bending moment, as well as other geometric constraints. In this paper, optimization of that case using a state-of-the-art constrained population-based global optimization framework is presented. Shape control is achieved via a hierarchical application of the radial basis function domain element approach. Three different fidelities of optimization cases are performed to investigate the multimodality of various aspects of the full problem, with four independent runs of each case being performed. When considering chord optimization, the optimizer converges to two independently identifiable minima with very similar performances. When adding dihedral and sweep variation, further multimodality is introduced, although this multimodality is reasonably well defined, with minima including forward and rearward sweeps, and an upward and a downward winglet. Introducing thickness variables leads to a highly multimodal problem due to the coupling between the chord and thickness variables. The theoretical minimum drag for this case is 24.7 counts, which a number of the runs gets close to achieving.