High-lift Configuration Research Articles

Aerodynamic-Aeroacoustic Optimization of a Baseline Wing and Flap Configuration

Optimization design was widely used in the high-lift device design process, and the aeroacoustic reduction characteristic is an important objective of the optimization. The aerodynamic and aeroacoustic study on the baseline wing and flap configuration was performed numerically. In the current study, the three-dimensional Large Eddy Simulation (LES) equations coupled with dynamic Smagorinsky subgrid model and Ffowcs–William and Hawkings (FW–H) equation are employed to simulate the flow fields and carry out acoustic analogy. The numerical results show reasonable agreement with the experimental data. Further, the particle swarm optimization algorithm coupled with the Kriging surrogate model was employed to determine optimum location of the flap deposition. The Latin hypercube method is used for the generation of initial samples for optimization. In addition, the relationship between the design variables and the objective functions are obtained using the optimization sample points. The optimized maximum overall sound pressure level (OASPL) of far-field noise decreases by 3.99 dB with a loss of lift-drag ratio (L/D) of less than 1%. Meanwhile, the optimized performances are in good and reasonable agreement with the numerical predictions. The findings provide suggestions for the low-noise and high-lift configuration design and application in high-lift devices.

Aerodynamic Shape Optimisation of a Camber Morphing Airfoil and Noise Estimation

In order to decrease the emitted airframe noise by a two-dimensional high-lift configuration during take-off and landing performance, a morphing airfoil has been designed through a shape design optimisation procedure starting from a baseline airfoil (NLR 7301), with the aim of emulating a high-lift configuration in terms of aerodynamic performance. A methodology has been implemented to accomplish such aerodynamic improvements by means of the compressible steady RANS equations at a certain angle of attack, with the objective of maximising its lift coefficient up to equivalent values regarding the high-lift configuration, whilst respecting the imposed structural constraints to guarantee a realistic optimised design. For such purposes, a gradient-based optimisation through the discrete adjoint method has been undertaken. Once the optimised airfoil is achieved, unsteady simulations have been carried out to obtain surface pressure distributions along a certain time-span to later serve as the input data for the aeroacoustic prediction framework, based on the Farassat 1A formulation, where the subsequent results for both configurations are post-processed to allow for a comparative analysis. Conclusively, the morphing airfoil has proven to be advantageous in terms of aeroacoustics, in which the noise has been reduced with respect to the conventional high-lift configuration for a comparable lift coefficient, despite being hampered by a significant drag coefficient increase due to stall on the morphing airfoil’s trailing edge.

Effectiveness of hazard control through HACCP critical control points in the wet noodle production process on product quality

The cavitation phenomena should be considered during the design of hydrokinetic turbines due to cavitation could cause surface erosion, mechanical vibrations, undesirable noise and efficiency reduction in the energy transformation. Therefore, the aim of this work is to conduct a numerical comparison of the cavitation resistance of 3 hydrofoils (NACA0015, Eppler420 and S822) with the purpose of selecting the best foil for the blade cross-section design. For each hydrofoil, the traditional and the high-lift configurations were evaluated. The hydrodynamic factors, including the lift and the drag (CL and CD, respectively) coefficients were determined by using JavaFoil software for several angles of attack (α). Additionally, for the computational fluid dynamics (CFD) study in ANSYs Fluent software, the SST k-ω and the Schnerr and Sauer turbulence and cavitation models were respectively utilized to validate the values of CL and CD, and to calculate the pressure coefficient (CP). The values of CP were compared with the cavitation number (σ) for identifying cavitation on the blade and comparing the cavitation resistance of the hydrofoils studied. The methods used and the numerical results obtained were subsequently analyzed and validated using relevant experimental values available in the literature for the NACA0015 hydrofoil. CFD simulations revealed that the NACA0015 traditional hydrofoil and the high-lift configuration of the Eppler420 hydrofoil have the best resistance to cavitation inception in comparison with the traditional hydrofoils and the high-lift configurations studied, respectively.

Comparative study of the cavitation resistance of the traditional and high-lift hydrofoils for hydrokinetic application

The cavitation phenomena should be considered during the design of hydrokinetic turbines due to cavitation could cause surface erosion, mechanical vibrations, undesirable noise and efficiency reduction in the energy transformation. Therefore, the aim of this work is to conduct a numerical comparison of the cavitation resistance of 3 hydrofoils (NACA0015, Eppler420 and S822) with the purpose of selecting the best foil for the blade cross-section design. For each hydrofoil, the traditional and the high-lift configurations were evaluated. The hydrodynamic factors, including the lift and the drag (CL and CD, respectively) coefficients were determined by using JavaFoil software for several angles of attack (α). Additionally, for the computational fluid dynamics (CFD) study in ANSYs Fluent software, the SST and the Schnerr and Sauer turbulence and cavitation models were respectively utilized to validate the values of CL and CD, and to calculate the pressure coefficient (CP). The values of CP were compared with the cavitation number (σ) for identifying cavitation on the blade and comparing the cavitation resistance of the hydrofoils studied. The methods used and the numerical results obtained were subsequently analyzed and validated using relevant experimental values available in the literature for the NACA0015 hydrofoil. CFD simulations revealed that the NACA0015 traditional hydrofoil and the high-lift configuration of the Eppler420 hydrofoil have the best resistance to cavitation inception in comparison with the traditional hydrofoils and the high-lift configurations studied, respectively.

Enhancing the High-lift Properties of a Supercritical Wing by Means of a Modulated Pulse Jet Actuator

In this experimental investigation, a pulse flow control system on a high-lift device of a wing with a NASA SC(2)-0714 airfoil within the Reynolds number range of the take-off and landing phases, is proposed. In this study, an innovative method of signal modulation has been used in order to simultaneously exploit the benefits of both low and high excitation frequencies in one actuator driving signal that are known to be effective in separation control. It is observed that the lift and drag coefficients are improved due to the use of modulated pulse jets compared to the simple pulse jet. Keywords: Flow Control, High-lift configuration, Pulsed jet, Burst modulation, aerodynamic efficiency

Aerodynamic Prediction of Aircraft High Lift Configuration Using Hierarchical Cartesian Grid and Immersed Boundary Method

In this study, the steady RANS simulation around CRM-HL is conducted to investigate the prediction capability of the hierarchical Cartesian grid flow solver to predict the aerodynamic performance of an aircraft high lift configuration. To calculate the turbulent boundary layer, the immersed boundary method and the wall function are used. Three types of grids are used, and their grid numbers are about 100M, 200M, and 400M. The calculated aerodynamic coefficients agreed well with the wind tunnel test results in the low angle of attack region. On the other hand, the calculated aerodynamic coefficients showed a discrepancy in the aerodynamics coefficients to the wind tunnel test at high angle of attack. In addition, grid convergence could not be confirmed for CD and CM at high angle of attack. However, the RANS method used in this paper is not a model which can capture physical phenomena related to separation. Hence, reasonable results for RANS were obtained semi-automatically through automatic grid generation.

Aerodynamic Prediction of High-Lift Configuration Using Turbulence Model

The aerodynamic performance of the high-lift configuration greatly influences the safety and economy of commercial aircraft. Accurately predicting the aerodynamic performance of the high-lift configuration, especially the stall behavior, is important for aircraft design. However, the complex flow phenomena of high-lift configurations pose substantial difficulties to current turbulence models. In this paper, an eddy-viscosity turbulence model is used to compute the stall behavior of high-lift configurations. A separated shear layer fixed function is implemented in the turbulence model to better capture the nonequilibrium characteristics of turbulence. Different high-lift configurations, including the two-dimensional multi-element NLR7301 and Omar airfoils and a complex full-configuration model (JAXA Standard Model), are numerically tested. The simulations show engineering accurate results and indicate that the effect of the nonequilibrium characteristics of turbulence is significant in the free shear layer, which is key to accurately predicting the stall behavior of high-lift devices. The modified shear layer fixed model is more accurate in predicting stall behavior than the Spalart–Allmaras, shear stress transport, and original models for the full high-lift configuration. The relative errors in the predicted maximum lift coefficients are within 3% of the experimental data.

Effect of a Variable-Bend Slat on Tones Due to the Cove’s Self-Excited Oscillation

AbstractTo study the noise reduction effect of a variable-bend slat, both experimental and numerical investigations are carried out on a two-dimensional high-lift configuration with a stowed flap a...

Computational Investigation of Conventional and Active-Flow-Control-Enabled High-Lift Configurations

The work presented in this paper is a culmination of a multiyear joint experimental and computational effort to explore the feasibility of using active flow control (AFC) on a simple hinged flap system for recovering lift comparable to a conventional high-lift system consisting of Fowler flaps. The baseline configuration chosen for this work is the high-lift version of the NASA Common Research Model (CRM), which is a representative modern aircraft consisting of wing, fuselage, nacelle/pylon, slats, Fowler flaps, and slat and flap brackets. A simplified high-lift (SHL) system was created by replacing the Fowler flaps and flap brackets with a simple hinged flap system equipped with integrated modular AFC cartridges on the suction surface of the flap shoulder, and the resulting geometry is known as the CRM–SHL–AFC configuration. Parametric studies were conducted in the earlier phases of this effort to numerically evaluate and downselect the more efficient AFC designs for wind-tunnel tests. These simulations were performed with the PowerFLOW® code, which is a lattice-Boltzmann-based computational fluid dynamics code. Good agreement was reported in a previous paper between the numerical results and the experimental data for the lift characteristics of the CRM–SHL–AFC configuration as a function of actuation levels at the nominal landing conditions. The current effort is focused on demonstrating the applicability of the PowerFLOW code for predicting the aerodynamic performance of the conventional and the AFC-enabled simplified high-lift CRM configurations for a broad angle of attack range, including maximum lift conditions.

Flow Parameters in Dominant Mode Selection of Self-Excited Oscillation in Slat Coves

This paper investigates self-excited oscillation within a slat cove and the flowfield parameters involved in selection of the main oscillation mode. Aeroacoustic experiments are described for aerodynamic noise characteristics on the leading-edge slat of a two-dimensional three-element high-lift configuration. Different geometrical settings are tested at varying angles of attack. A numerical simulation method is used as an auxiliary tool to analyze the flowfield. Based on previous research results and the experimental results obtained in this paper, a ratio of is proposed to evaluate the main mode of self-excited oscillation, where is the shear-layer length within the slat cove, is the boundary-layer thickness near the point of separation, and is the ratio of average vortex convection velocity along the shear layer to the maximum velocity in the shear layer near the cusp. The relationship between the aforementioned ratio and the main mode of oscillation is verified by far-field noise data for a high-lift configuration with different geometrical settings. As the slat translation along the chordwise direction of the main wing increases, the ratio also increases; and the main mode of self-excited oscillation switches from mode II to a transition phase, and then to mode III.

Numerical analysis of high-lift configurations with oscillating flaps

This study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport k-omega turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of 0.5 times 10^{6} the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of 20 times 10^6, reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

An optimal heat-flux targeting procedure for LEO re-entry of reusable vehicles

This paper addresses the feasibility analysis of a re-entry flight strategy from low Earth orbit, developed for an innovative re-usable wing-body concept, having a rather high surface-to-mass ratio. The re-entry procedure envisages a longer and gradual dissipation of vehicle's total energy, carried out at a flight path angle lower than typical Shuttle-like values. Hence, the heat flux is kept constant at a predicted threshold, thus allowing the radiative cooling of the spacecraft heatshield at a suitable temperature. The selected flight approach relies on a prescribed guidance law which modulates the glider angle of attack as function of Mach number, to assure the desired convective heat flux level for a certain time. Based on a low-flight path assumption, analytical considerations are derived to evaluate geometric, aerodynamic, and flight parameters that influence the convective heat flux. Furthermore, candidate guidance laws are determined formulating an optimization-based heat flux targeting procedure. The relevance of aerodynamic performances is also underlined, provided that, by results high lift configurations dictate lower angles of attack and vice versa. Analytical and numerical results evidence existing relation between surface-to-mass ratio, lift-to-drag ratio and flight duration time, that can be used “on design” to modulate the aerothermal loading. The current approach is suitable to explore less challenging aerothermal environments in order to improve reliability and affordability of space operations in the near Earth space.

Implicit large Eddy simulation of the NASA CRM high-lift configuration near stall

Recent progress in adaptive high-order numerical methods, high-order mesh generation, and scalable implicit time integration approaches has made large eddy simulation (LES) more affordable than ever before. In the present study, we demonstrate the progress by performing implicit LES of a benchmark problem from the 3rd AIAA High-Lift Prediction Workshop: NASA's Common Research Model (CRM) high-lift configuration. The LES tool, hpMusic, is based on the flux reconstruction method capable of handling high-order mixed unstructured meshes. P-refinement studies are used to assess the mesh-dependence of the numerical solutions. Comparisons are also made with available experimental data, and a very good agreement was obtained in lift and drag coefficients between the present computation and wall-corrected experimental data.

Dynamic Stall on High-Lift Airfoil 30P30N in Ground Proximity

Computational prediction of stall aerodynamics in free air and in close proximity to the ground considering the 30P30N three-element high-lift configuration is carried out based on CFD simulations using the OpenFOAM code and Fluent software. Both the attached and separated flow regimes are simulated using the Reynolds Averaged Navier-Stokes (RANS) equations closed with the Spalart-Allamaras (SA) turbulence model for static conditions and pitch oscillations at Reynolds number, Re = 5 x 106 and Mach number, M = 0.2. The effects of closeness to the ground and dynamic stall are investigated and the reduction in the lift force in close proximity to the ground is discussed.

Reynolds number and wind tunnel wall effects on the flow field around a generic UHBR engine high-lift configuration

RANS simulations of a generic ultra-high bypass ratio engine high-lift configuration were conducted in three different environments. The purpose of this study is to assess small scale tests in an atmospheric closed test section wind tunnel regarding transferability to large scale tests in an open-jet wind tunnel. Special emphasis was placed on the flow field in the separation prone region downstream from the extended slat cut-out. Validation with wind tunnel test data shows an adequate agreement with CFD results. The cross-comparison of the three sets of simulations allowed to identify the effects of the Reynolds number and the wind tunnel walls on the flow field separately. The simulations reveal significant blockage effects and corner flow separation induced by the test section walls. By comparison, the Reynolds number effects are negligible. A decrease of the incidence angle for the small scale model allows to successfully reproduce the flow field of the large scale model despite severe wind tunnel wall effects.

Prediction Capability of Cartesian Cut-Cell Method with a Wall-Stress Model Applied to High Reynolds Number Flows

The Cartesian cut-cell method is one of the most promising methods for computational fluid dynamics due to its sharp interface treatment. However, the Cartesian cut-cell method and other Cartesian mesh solvers have difficulty with concentrating grid to boundary layers. The wall-modelling of shear stress is one of the most effective methods to reduce computational grids in boundary layers. This study investigated the applicability of a wall-stress model to the Cartesian cut-cell method. In the numerical simulations of the flow around a triangular column, Cartesian cut-cell simulation with the wall-stress model adequately predicted the drag coefficient. In the numerical simulations of the flow around a 30P30N high-lift airfoil configuration, the Cartesian cut-cell simulation with the wall-stress model adequately predicts the lift coefficient. The intermittent vortex structure of the outer layer of the turbulent boundary layer was observed on the suction side of the main element and the flap. The Cartesian cut-cell method with a wall-stress model is useful for predicting high Reynolds number flows at R e ∼ 10 6 .

Active flow control for external aerodynamics: from micro air vehicles to a full aircraft in stall

We investigate the aerodynamic performance of active flow control of airfoils and wings using synthetic jets with zero net-mass flow. The study is conducted via wall-resolved and wall-modeled large-eddy simulation using two independent CFD solvers: Alya, a finite-element-based solver; and charLES, a finite-volume-based solver. Our approach is first validated in a NACA4412, for which numerical and experimental results are already available in the literature. The performance of synthetic jets is evaluated for two flow configurations: a SD7003 airfoil at moderate Reynolds number with laminar separation bubble, which is representative of Micro Air Vehicles, and the high-lift configuration of the JAXA Standard Model at realistic Reynolds numbers for landing. In both cases, our predictions indicate that, at high angles of attack, the control successfully eliminates the laminar/turbulent recirculations located downstream the actuator, which increases the aerodynamic performance. Our efforts illustrate the technology-readiness of large-eddy simulation in the design of control strategies for real-world external aerodynamic applications.

Numerical investigation of frequency-amplitude effects of dynamic morphing for a high-lift configuration at high Reynolds number

PurposeThe purpose of this study illustrates the morphing effects around a large-scale high-lift configuration of the Airbus A320 with two elements airfoil-flap in the take-off position. The flow around the airfoil-flap and the near wake are analysed in the static case and under time-dependent vibration of the flap trailing-edge known as the dynamic morphing.Design/methodology/approachExperimental results obtained in the subsonic wind tunnel S1 of Institut de Mécanique des Fluides de Toulouse of a single wing are discussed with high-fidelity numerical results obtained by using the Navier–Stokes multi-block (NSMB) code with advanced turbulent modelling able to capture the predominant instabilities and coherent structure dynamics. An explanation of the dynamic time-dependent grid deformation is provided, which is used in the NSMB code to simulate the flap’s trailing-edge deformation in the morphing configuration. Finally, power spectral density is performed to reveal the coherent wake structures and their modification because of the morphing.FindingsFrequency of vibration and amplitude of deformation effects are investigated for different morphing cases. Optimal morphing regions at a specific frequency and a slight deformation were able to attenuate the predominant natural shear-layer frequency and to considerably decrease the width of the von Kármán vortices with a simultaneous increase of aerodynamic performances.Originality/valueThe new concept of future morphed wings is proposed for a large scale A320 prototype at the take-off position. The dynamic morphing of the flap’s trailing-edge is simulated for the first time for high-lift two-element configuration. In addition, the wake analysis performed helped to show the turbulent structures according to the organised eddy simulation model.

Aerodynamic performance Augmentation of Supersonic Transport by High lift Configurations for Fuselage

Aerodynamic performance Augmentation of Supersonic Transport by High lift Configurations for Fuselage

Performance of the k-kL model for aerodynamics applications

PurposeThe purpose of this paper is to study the predictability of the recently proposed length scale-based two-equation k-kL model for external aerodynamic flows such as those also encountered in the high-lift devices.Design/methodology/approachThe two-equation k-kL model solves the transport equations of turbulent kinetic energy (TKE) and the product of TKE and the integral length scale to obtain the effect of turbulence on the mean flow field. In theory, the use of governing equation for length scale (kL) along with the TKE promises applicability in a wide range of applications in both free-shear and wall-bounded flows with eddy-resolving capability.FindingsThe model is implemented in the in-house unstructured grid computational fluid dynamics solver to investigate its performance for airfoils in difficult-to-predict situations, including stalling and separation. The numerical findings show the good capability of the model in handling the complex flow physics in the external aerodynamic computations.Originality/valueThe model performance is studied for stationary turbulent external aerodynamic flows, using five different airfoils, including two multi-element airfoils in high-lift configurations which, in the knowledge of the authors, have not been simulated with k-kL model until now.