Biplane Configuration Research Articles

Conceptual design of a third generation aerobatic aircraft

This paper presents the development of an aerobatic aircraft including the influence of platform configuration on performance, elegance and safety of aerobatic manoeuvres. Several aircraft of different wing loadings were compared and the reduction of wing loading on manoeuvring slowdown was studied. Advantages of the biplane configuration influence on the desired properties of aerobatic aircraft were discussed in detail. Results of numerical simulations obtained for HARNAS-3 aircraft were compared with corresponding results received for EXTRA 300 aircraft. Some original design solutions for HARNAS-3, enabling easier control of this aircraft during the manoeuvring phase, were presented. Numerical simulations, wind tunnel tests and free flight experimental results for scaled-down HARNAS-3 models were presented, compared and discussed.

Aeroelastic modeling and analysis of wings in proximity

This study investigates the effects of aerodynamic interaction on the aeroelastic characteristics of wings in proximity which is considered to be aerodynamically more efficient than the single wing case. The structural model of the wing is based on the first-order shear deformation theory and analyzed by the finite element method. The flow surrounding the wings is governed by potential theory and the aerodynamic loads are computed using the unsteady vortex lattice method. The aeroelastic simulation framework is established by integrating the structural and aerodynamic models within the flexible multibody dynamic program to solve the aeroelastic equations of motion in the time domain. Cantilever wings in proximity, arranged in biplane configuration, with different geometric parameters such as gap, sweep angle, dihedral angle, and stagger are considered in the analysis. The numerical results show that the smaller gap between the wings magnifies the aerodynamic interaction effect and decreases the onset of flutter speed. Sweeping the wing backward further reduces the flutter boundaries of the biplane model mainly due to changes in the wing's structural modal whereas the effect of dihedral angles is understated. The effect of stagger is more evident for a smaller gap and mostly leads to an increase in the flutter boundary. The aeroelastic responses are independent of initial disturbance and show a natural tendency to oscillate with a phase difference. This investigation warrants the importance of considering biplane wings as a single system for a gap lower than wing chord length as well as the significance of other geometric parameters in the aeroelastic calculation.

Selection Criteria for Biplane Wing Geometries by Means of 2D Wind Tunnel Tests

This paper presents a study based on wind tunnel research on biplane configurations. The objective of this research is to establish an experimental basis for relationships between the main geometrical parameters that define a biplane configuration (stagger, decalage, gap, and sweep angle) and the aerodynamic characteristics (CL, CD). This experimental study focuses on a 2D approach. This method is the first step towards dealing with the issue, and it allows the variables involved in the tests to be reduced. The biplane configuration has been compared with the monoplane configuration to analyze the viability for implementing the biplane configuration in the field of application for micro air vehicles (MAV). At present, the biplane and other unusual configurations have not been a common design for MAV; however, they do have unlimited future potential. A set of experimental tests were carried out on various biplane configurations at low Reynolds numbers, which allowed the criteria for selecting the best wing configuration to be defined. The results obtained here show that the biplane configuration provides a higher maximum lift coefficient (CLmax) than the planar wing (monoplane). Furthermore, it has a larger wetted surface than the planar configuration, so the parasitic drag increases for the biplane configuration. This research is focused on a drone flight regime (low Reynolds number), and in this case, the parasitic drag (profile drag) has an important role in the total drag of the airplane. This study considers whether the reduction in the induced drag due to three–dimensional configuration (biplanes, box–wings, and joined–wings) can reduce the total drag or if the increase in the parasitic drag is bigger. Additionally, the increase in lift and the decrease in parasitic drag (profile drag) will be studied to determine if they have a greater influence on the performance of the airplane than the increase in structural weight. Further research is planned to be performed on 3D prototypes, with the selected configurations, and applied to nonconventional wing planforms.

Effect of Stagger on Low-Speed Performance of Busemann Biplane Airfoil

In this study, the low-speed performances of the Busemann biplane were clarified, focusing on the relative contributions of the upper and lower elements to the total aerodynamic characteristics of the biplane. Also, the effects of the staggered biplane, which changes the horizontal distance between two wings in a biplane configuration, were investigated by balance measurements and numerical simulations. The flow velocity was 15 m/s, and the Reynolds number based on the airfoil chord length was 2.1 × 105. In the tests of the integrated biplane wing, the attack angles of the wing elements were varied by a balance system and turntable, which were set in the wind tunnel sidewall. The results show that the lower element generated most of the lift and drag of the Busemann biplane (or the baseline biplane model with no stagger) at high angles of attack. At angles above 20 deg, the contribution of the lower element to total aerodynamic characteristics is almost constant, with 95% of the total lift and 88% of the total drag. The total lift and drag of the baseline model were smaller than the sum of the individual elements that were treated as a single configuration. The increments of lift and drag due to the stagger effects were confirmed, especially at high angles of attack. When the stagger value increases, the high-pressure area near the leading edge of the lower surface of the upper element also increases, which increases the lift and drag of the up-per element. This is the main reason for the increments of total lift and drag of the biplane model. The stagger effects also prevented the leading-edge separation of the lower element in the biplane configuration and increased the lift slopes of the biplane model.

Propulsive performance of plunging airfoils in biplane configuration

Biplane configuration of pure plunging airfoils is investigated in terms of vortex dynamics both experimentally and numerically by utilizing particle image velocimetry and unstructured finite volume solver of incompressible unsteady Navier–Stokes equations. Experiments are carried out to disclose the vortex shedding and interaction mechanisms for various values of frequency and amplitude of the plunging motion. For the non-dimensional plunge amplitude with respect to the chord of airfoil h = 0.2, the effect of the reduced circular frequency based on chord length and the free stream velocity k = 1 and 10 are considered, whereas for h = 0.3, k = 2, 4, 8, and 10 cases are examined. Influence of the plunge amplitude is studied for h = 0.25 at k = 2.5 and for h = 0.0875, 0.15, and 0.3 at k = 4. Numerical simulations are performed to investigate the effect of phase difference on vortex structures and propulsive characteristics, such as thrust and Froude efficiency. Two cases having the highest thrust and efficiency values k = 2.5, h = 0.25, and k = 4, h = 0.15 value couples are selected for the phase angle of ϕ=0°, ϕ=90°, ϕ=180°, and ϕ=270°. Opposed plunge, ϕ=180°, was found as the most efficient amongst all phase angles that were investigated, where ϕ=90° is beneficial in lift production. Additionally, three-dimensional simulations indicate no significant three dimensionalities for the parameters used herein.

Numerical investigation on buffeting and lock-in phenomenon for biplane airfoils at [formula omitted

Biplane airfoils at high angles of attack have interesting nonlinear characteristics, the purpose of this work is to evaluate the impacts of spacing ratio (λ=ds/c=0.25, 0.5, 1, 2 and 4, where ds is the vertical distance between biplane airfoils and c is chord length) and Reynolds number (0.87×105≤Re≤4.35×105) on buffeting and lock-in phenomenon at angle of attack α=40∘ throughout numerical investigation. Present simulation results show that biplane configuration usually can reduce buffeting frequency slightly comparing to the single airfoil, yet reasonable spacing λ=2 is helpful to suppress buffeting and continuous acceleration also promotes stability. Particular attention is paid to stagnation point region that moves away from leading edge of the upper airfoil with increasing λ. However, the lower airfoil corresponds to the fixed stagnation point region. Additionally, limit cycle oscillation (LCO) of biplane airfoils is determined by pitching angles (θ), and in consideration of spacing effect, limit cycles of the lower airfoil move downward but those of the upper airfoil move in the opposite direction. Moreover, the shape of limit cycle for the later first collapses then inflates. Unique 8-shaped hysteresis of the upper airfoil in λ=1 is caused by sporadically wake interference. On the whole, V-shaped lock-in region will expand and shift left to some extent based on λ in contrast to the single airfoil. In terms of area, lock-in region shrinks then expands with rising λ, and the proportion of the left part increases as λ increases.

Analysis of a Wing–Fuselage Biplane with Trailing-Edge Flaps in Low-Speed Flow

In this paper, the low-speed aerodynamic characteristics of a basic wing–fuselage supersonic biplane incorporating trailing-edge flaps are assessed using both wake and balance measurements. The effects of the flap attachment location, flap deflection, and flap length are evaluated. These experiments employed a flow velocity of and a Reynolds number of , along with a model having a simple three-dimensional wing–fuselage supersonic biplane configuration; and wake data were obtained with a five-hole probe. Installing the flap near the wingtip was found to produce strong interactions between the wingtip and the flap vortices in the wake, leading to significant induced drag at the wingtip. The local lift increases not only at the flap attachment location but also over the entire wingspan. Positioning the flaps near the body is determined to be more effective, and it gives rise to higher lift and smaller drag than in the case of installing the flap near the wingtip, due to the effects of the tapered wing configuration. The effects of the flap length and flap deflection are also confirmed, with longer flaps and larger flap deflection giving higher lift and more drag.

Numerical investigation of aerodynamics and wake on biplane airfoils at high angles of attack

Biplane configuration is a critical configuration for aircrafts all the time, but the dynamics and flow mechanism remain elusive, with no systematic description forthcoming. This paper reported a numerical investigation of spacing effect (λ=d/c=0.4∼5, c is the chord length and c=6inch) and the mean and fluctuating aerodynamics for biplane airfoils at angles of attack ranging from 30∘ to 90∘. Additionally, particular attention was devoted to vorticity fields and Strouhal number (St). The primary finding was that C¯L and C¯D of the lower airfoil were greater than those of the upper airfoil whatever λ was located to. And the turning points for C¯L and C¯D of the upper airfoil showed an evident regularity with increasing λ.But the maximum deviation first plungs then jumps with increasing λ. What inspired us was the fluctuating aerodynamics in λ=1.5 converged quickly which may contribute to enhancing stability. Interestingly, overall lift-to-drag ratio trends in all cases were strikingly similar to a single airfoil. Three vortices regimes were identified from the generation mechanism of traling-edge vortices (TEVs), named integrated vortices, transition with deformed vortices and coshedding vortices, respectively. And the vortices regime was also related to the angle of attack. Besides, in the integrated and coshedding vortices regimes, two Strouhal numbers of the lower airfoil and the upper airfoil were equivalent, but St can’t be estimated which one is larger in the transition regime.

Meshfree method based on discrete gas-kinetic scheme to simulate incompressible/compressible flows

A meshfree method based on the discrete gas-kinetic scheme (DGKS) (called the meshfree-DGKS) for simulation of incompressible/compressible flows is proposed in this work. In this approach, the governing equations are discretized using the meshfree method based on the least squares-based finite difference approach. To simulate compressible problems with discontinuities, the virtual mid-points between adjacent nodes, which are regarded as Riemann discontinuities, are established. Then, the concept of numerical flux is introduced, which enables computing both compressible and incompressible problems. The fluxes at the mid-points are calculated using the DGKS based on the discrete particle velocity model. The corresponding particle velocity components and distribution functions are integrated based on moment relations to obtain the flux. The meshfree-DGKS maintains the advantages of the meshless method as it is implemented at arbitrarily distributed nodes. This breaks through the limitations of the grid topology and is suitable to handle complex geometries. More importantly, the fluxes at the mid-point are reconstructed with the DGKS using the local solution of the Boltzmann equation, which can describe its physical properties well, thus easily and stably capturing the shock wave. In addition, the DGKS can simultaneously calculate inviscid and viscous fluxes when simulating viscous flow problems, which gives an improved algorithm consistency. Several representative examples, such as shock tube problems, implosion problem, couette flow, lid-driven cavity flow, flow in a channel with a backward-facing step, supersonic flow around a ramp segment, and flow around staggered NACA0012 biplane configuration, are simulated to validate the proposed meshfree-DGKS.

Meshfree lattice Boltzmann flux solver for compressible inviscid flows

AbstractIn this work, a meshfree Lattice Boltzmann Flux Solver (LBFS) is proposed to resolve compressible flow problems based on scattered points without mesh connections. The new method employs the Least Square‐based Finite Difference (LSFD) scheme to discretize the governing equations. In order to simulate discontinuous problems such as shock wave, the mid‐point between two adjacent nodes is regarded as a discontinuous interface over which the Riemann problem is established. The local fluxes at this interface point are reconstructed by LBFS using the local solution of the Lattice Boltzmann Equation (LBE) as well as its correlations to macroscopic variables and moment relations. The LBFS is constructed based on the non‐free parameter D1Q4 model: the normal component of the particle velocity on the interface is retained, while the tangential component is reconstructed by the macroscopic variables on both sides of the interface. The meshfree LBFS expects some intriguing merits. On one hand, it inherits the physical robustness of the LBFS: the local fluxes are reconstructed from the physical solutions instead of mathematical interpolations. On the other hand, it allows the implementation at arbitrarily distributed nodes, which credits to the flexibility of the method. Representative examples of compressible flows, including Sod shock tube, Osher‐Shu shock tube, flow around NACA0012 airfoil, flow around staggered NACA0012 biplane configuration and shock reflection problem, are simulated by the proposed method for comprehensive evaluation of the meshfree LBFS.

Power extraction performance of two semi-active flapping airfoils at biplane configuration

The power extraction performance of two semi-active flapping airfoils at biplane configuration is analyzed in this work through numerical approach. Two NACA0015 airfoils, which are regarded as an energy extraction turbine, are arranged in a biplane configuration to perform forced counter pitching motion and are subsequently induced in a plunging motion. A numerical code based on finite volume method to solve the Navier-Stokes equations coupled with finite center difference method to solve the passive plunging motion governing equation is developed to simulate the interaction between the two semi-active flapping airfoils and fluid. Results show that the semi-active flapping airfoil cannot absorb more power from the fluid with biplane arrangement, but this arrangement is beneficial for the power extraction efficiency of the airfoil. Analysis of the fluid field of the airfoil reveals that the wing-wing interaction can promote the vortex evolution and reduce the vortex magnitude of the suction side of the biplane airfoils with appropriate initial distance (hs = 2.5d). As a result, the maximum plunging of the biplane airfoils is smaller than that of the single airfoil. The smaller maximum plunging displacement contributes to the increase in power extraction efficiency.

Avoiding Choked Flow and Flow Hysteresis of Busemann Biplane by Stagger Approach

This study establishes a method to overcome the choked-flow and flow-hysteresis problems of the Busemann biplane at offdesign conditions during its acceleration and deceleration processes. Two-dimensional analyses of Busemann-type biplanes have been addressed using the application of a computational fluid dynamics code in both inviscid and viscous flow modes. The effect of stagger on the aerodynamic characteristics of the Busemann biplane is validated. The biplane with the continuous stagger approach shows a lower drag coefficient during the acceleration process as compared with the baseline Busemann biplane and the diamond airfoil. The results also show that this strategy is efficient to reduce the choked-flow and flow-hysteresis problems for the biplane configuration at the offdesign condition.

First-principles study of interfacial energy between alpha-zirconium and zirconium hydride

The interfacial energies among α-Zr, ζ-, γ′-, γ-, and δ-phase zirconium hydride have been calculated via first-principles calculations. Hydrogen biplane configurations of ζ and γ′ are confirmed by binding energy calculations. Based on binding energy calculations and convex hull plots, the ζ phase is not a local stable configuration, and ZrH0.4 is more stable. ζ can be viewed as composed of α and γ′, as well as α∣γ′ interfaces with a 65 mJ/m2 interfacial energy. Thus, ζ is less stable than γ′, assuming no hcp-fct/fcc transformation occurred. Based on the calculated convex hull plots, γ is more stable than δ. The negative interfacial energy between ζ (or γ′) and δ may promote the δ hydride formation.

Numerical investigation of auto-pitch wing-in-ground effect oscillating foil propulsor

The propulsive characteristics of auto-pitch wing-in-ground effect oscillating foil propulsors (APWIGs) were numerically investigated through an unsteady Reynolds Averaged Navier-Stokes solver. The kinematics of such a biplane configuration is characterized by the prescribed heave motion and flow-induced pitch motion restrained by a torsional spring for each foil. Based on the validated numerical model, the comparison of propulsive performance between APWIGs and single auto-pitch oscillating foil, as well as dual-foil heave-only configuration, was conducted at different advance speeds. Results show that APWIGs is advantageous in both thrust production and efficiency enhancement over other two configurations due to the resulting wing-in-ground effect and substantial reduction of flow separation by the flow-regulated pitch motion. Furthermore, the effect of torsional spring stiffness on the propulsion of APWIGs was studied under different loaded conditions. It was found that both the maximum pitching angle and phase difference of pitch with heave are dramatically affected by the spring stiffness, which has major contribution to the hydrodynamic behaviours of the foils. Under a certain operating speed, an optimal torsional spring stiffness that produces the best propulsive performance can be found. With respect to the parametric space in the current study, the APWIGs can achieve a constant high efficiency over 70% by employing an appropriate spring stiffness.

겹 날개를 사용하는 곤충 모방 비행체의 날개 형상에 대한 파라메트릭 연구

본 논문에서는 곤충 모방 날갯짓 비행체의 가장 중요한 설계 변수 중 하나인 날개에 대한 파라메트릭 연구에 대해 서술하였다. 추력, 피칭모멘트, 소비전력, 추력 대 전력비의 비교 및 분석을 통해 날개 형상에 대한 실험적 연구를 진행하였다. 힘과 모멘트는 2축 밸런스를 이용하여 측정되었으며 날갯짓 주파수는 홀센서를 이용하여 측정되었다. 날개 형태는 겹 날개 형태를 채택하였으며 이를 통해 Clap and fling 효과를 구현하였다. 기준 날개 형상으로 잠자리의 날개를 선정하였고, 이를 기준으로 가로세로비 및 면적에 대한 실험을 진행하였다. 결과적으로, 가로세로비와 면적이 증가할수록 추력, 피칭모멘트, 소비전력이 증가하는 것을 확인하였다. 또한, 일정 수준 이상의 가로세로비 혹은 면적을 가지는 날개를 메커니즘에 적용하였을 때 메커니즘이 정상적으로 구동되지 않는 것을 확인하였다. 최종적으로 날개 형상 선정은 필요한 최소추력을 만족시키는 날개 중에서 추력 대 전력비를 비교함으로써 이루어졌다. 하지만 추력선과 무게중심의 불일치로 인한 모멘트의 발생으로 안정성을 확보할 수 없었다. 이에 안정성을 확보하기 위해 상단과 하단에 댐퍼를 부착한 실내 비행시험을 통해 날개의 파라메트릭 연구 결과에 대한 간접적인 성능 검증을 수행하였다.

Effect of Wing-Wing Interaction on the Propulsive Performance of Two Flapping Wings at Biplane Configuration.

The biplane counter-flapping wing is a special type of wing flapping which is inspired from the fish and insect in nature. The propulsive performance is one of the most important considerations for this kind of flapping wing. This paper is aimed at providing a systematic synthesis on the propulsive characteristics of two flapping wings at biplane configuration based on the numerical analysis approach. Firstly, parameters of this special flapping wing are presented. Secondly, the numerical method for simultaneously solving the incompressible flow and counter-flapping motion of the wing is illustrated, and the method is then validated. Thirdly, the effects of phase angle and mean wing spacing on the propulsive characteristics of the biplane counter-flapping wing are analyzed. Finally, the quantification effects of the phase angle and mean wing spacing on the propulsive characteristics of the biplane counter-flapping wing can be obtained. The analysis results in this study will provide useful guidelines to design an effectively propulsive system applying for the flapping micro air or underwater vehicle.

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.

Numerical Investigation on the Propulsive Performance of Biplane Counter-Flapping Wings

A numerical investigation is performed to address the flexing effect on the propulsion performance of flapping wing particularly on the counter-flapping wings of the biplane configuration. A Reynolds number of 10,000 is considered in the present study which corresponds to the flight regime of most existing flapping wing micro air vehicles. The computation involves solving the compressible unsteady Reynolds- averaged Native-Stokes equation using an inhouse developed code. The flapping motion is incorporated by an efficient deforming overset grid technique which allows multiple flexible bodies to be embedded into the flow field. Results show that the biplane wing with counter-flapping configuration has a better propulsive performance in comparison to a single flapping wing. A low-pressure regime between the two wings during the outstroke produces more thrust, while the counter-flapping motion can also generate a surfeit momentum rushing in to the wake. The more flexible wing can produce more thrust while less power is required thus owning a better propulsive performance.

Numerical Analysis of Static and Dynamic Performances of Grid Fin Controlled Missiles

Grid fins provide good maneuverability to missiles in supersonic flow because they can maintain lift at a higher angle of attack. Although static aerodynamic data exist, very little quantitative dynamic performance information is available for grid fin controlled missiles. The high drag associated with grid fins is also a concern. Dynamic simulations are carried out using computational fluid dynamics to investigate the dynamic stability of a generic missile, controlled by grid fins or planar fins, in supersonic and transonic regimes at angles of attack up to 30 deg. In supersonic flow, the pitch-damping derivative is found to be insensitive to the control fin type; however, in transonic flow, grid fins provide a lower damping in pitch than planar fins due to the blockage effect induced by its choked cells. The reduction of the high drag associated with grid fins is also investigated by comparing the performances of two isolated grid fin geometries with and without the use of a Busemann biplane configuration. The application of this concept to grid fins reduces its drag in the supersonic regime while maintaining its beneficial lift characteristics. Furthermore, the drag of grid fins in transonic flow can be reduced by using an optimized profile with a higher inlet-to-throat area ratio.

Numerical simulation of a flapping four-wing micro-aerial vehicle

A three-dimensional numerical simulation of a four-wing (two wings on each side, one on top of another) flapping micro-aerial vehicle (FMAV), known as the Delfly micro, is performed using an immersed boundary method Navier–Stokes finite volume solver at Reynolds numbers of 5500 (forward flight condition). The objective of the present investigation is to gain an insight to the aerodynamics of flapping wing biplane configuration, by making an analysis on a geometry that is simplified, yet captures the major aspects of the wing behavior. The fractional step method is used to solve the Navier–Stokes equations. Results show that in comparison to the Delfly II flapping kinematics (a similar FMAV configuration but smaller flapping stroke angles), the Delfly-Micro flapping kinematics provides more thrust while maintaining the same efficiency. The Delfly-Micro biplane configuration generates more lift than expected when the inclination angle increases, due to the formation of a uniform leading edge vortex. Estimates of the lift produced in the forward flight conditions confirm that in the current design, the MAV is able to sustain forward flight. The potential effect of wing flexibility on the aerodynamic performance in the biplane configuration context is investigated through prescribed flexibility in the simulations. Increasing the wing׳ spanwise flexibility increases thrust but increasing chordwise flexibility causes thrust to first increase and then decrease. Moreover, combining both spanwise and chordwise flexibility outperforms cases with only either spanwise or chordwise flexibility.