Airfoil Configuration Research Articles

High-Fidelity Simulations of a Slotted, Natural-Laminar-Flow Wing Section

Numerical calculations are carried out to describe the subsonic flow over a wing section with a slotted, natural-laminar-flow airfoil geometry. The two-element airfoil configuration can maintain an extended laminar-flow region and thereby attain high maximum lift with low profile drag. However, such sections may be susceptible to adverse effects in the low-drag regime. Time-accurate simulations are performed to investigate the flowfield about the configuration and to describe its behavior. High-fidelity solutions are obtained to the unsteady three-dimensional Navier–Stokes equations at a chord-based Reynolds number of 1.0×106 and freestream Mach number of 0.1, which correspond to experimental conditions. For comparison, several angles of attack are considered, and features of the flowfields are elucidated. A grid-resolution study is conducted to assure the accuracy of the computations, and results are compared to experimental measurements. The effect of boundary-layer tripping is investigated, and the flow through the slot is examined. The time-accurate simulations identified no adverse behavior of the slotted configuration.

Numerical investigation of aerodynamic performance in a morphing wing with flexible leading edge using computational fluid dynamics

In this study, a numerical investigation into the sustained aerodynamic performance of a morphing wing equipped with a flexible leading edge, employing a 2-dimensional NACA0012 airfoil configuration, is conducted. The compressible governing equations of the flow are employed, simulating 2 distinct states: the airfoil without motion and the airfoil featuring a flexible leading edge with a chord length of 0.856 m, assessing various angles of attack utilizing the k-ω SST turbulence approach within Fluent software. Dynamic mesh, facilitated by a user-defined function, is utilized in Fluent software to simulate the movement of the airfoil wall at the leading edge. The study thoroughly analyzes the flow behavior concerning diverse angles of attack and deviations, evaluating their impact on aerodynamic coefficients, velocity, and pressure fields under steady-state settings. Validation of the chosen numerical approach demonstrates close alignment of the front and back coefficients with experimental settings. Outcomes from the steady-state flow simulation of the morphing wing reveal that positive deflection angles correspond to increased lift coefficients and decreased drag coefficients, with lift coefficient increases of up to 15% and drag coefficient reductions of up to 10% at specific angles. Meanwhile, the negative deflection angles have shown a decline in lift coefficients, with the drag coefficients increasing with the decrease in deflection angle. All these observations show that at the flexible leading edge, there is a considerable improvement in aerodynamic efficiency. Hence, it should find more applications in different regimes of flight.

Characterization of noise sources in two- and three-element high-lift airfoil configurations

Characterization of noise sources in two- and three-element high-lift airfoil configurations

Surrogate based design space exploration and exploitation for an efficient airfoil optimization under uncertainties using transition models

Surrogate based design space exploration and exploitation for an efficient airfoil optimization under uncertainties using transition models

A bioinspired triboelectric wireless anemometer with low cut-in wind speed for meteorological UAVs

A bioinspired triboelectric wireless anemometer with low cut-in wind speed for meteorological UAVs

Experimental investigation of multi-step airfoils in low Reynolds numbers applications

Experimental investigation of multi-step airfoils in low Reynolds numbers applications

Numerical analysis of thermal-hydraulic influence of geometric flow baffles on multistage Tesla valves in printed circuit heat exchangers

Numerical analysis of thermal-hydraulic influence of geometric flow baffles on multistage Tesla valves in printed circuit heat exchangers

Aerodynamic Prediction of the High-Lift Common Research Model with Modified Turbulence Model

Aerodynamic simulations were carried out in the study presented in this paper focusing on the stall performance of the High-Lift Common Research Model obtained from the fourth AIAA High-Lift Prediction Workshop. Various turbulence models of Reynolds-averaged Navier–Stokes simulations are analyzed. A modified version of the transitional k−v2¯−ω model was developed to enhance stall prediction accuracy for high-lift configurations with a nacelle chine. The vortex generator, three-element airfoil, and high-lift model are numerically simulated. The results reveal that implementing a k−v2¯−ω model with the separation shear layer fixed notably enhances the stall prediction behavior for both the three-element airfoil and high-lift configuration without affecting the prediction of the vortex strength of a vortex generator. Moreover, incorporating rotation correction into the SPF k−v2¯−ω model improves the prediction of vortex strength and further enhances stall prediction for the high-lift configuration. The relative error in predicting the maximum lift coefficient is less than 5% of the experimental data. The study also investigated the impact of the nacelle chine on the stall behavior of the high-lift configuration. The results demonstrate that the chine vortex can mitigate the adverse effects of the nacelle/pylon vortex system and increase the maximum lift coefficient.

Experimental Investigation on the Aerodynamic Parameters of Trailing Edge Wake Generators

In the realm of aerodynamics, the investigation of airfoil performance stands as a critical domain, with an ever-growing emphasis on optimizing designs for enhanced efficiency. This study investigates the aerodynamic performance of a NACA 0015 airfoil featuring various trailing edges, including serration, comb, poro-serration, and comb-serration. The experiments were conducted in a wind tunnel at angles of attack ranging from -15° to 15° and Reynolds numbers of 1.5 x 105 and 2.0 x 105. To accurately quantify the forces and moments acting on the airfoil models, a calibrated six-component balance was utilized to measure the aerodynamic coefficients of each airfoil configuration. The lift coefficient (cl), drag coefficient (cd), and pitching moment coefficient (cm) are analyzed for the various trailing edge types and Reynolds numbers. Results indicate that the baseline model demonstrated better aerodynamic performance compared to other types of trailing edge. Most trailing edges, except the baseline, resulted in a decrease in the lift coefficient. However, at very low angles of attack, the airfoil showed an improvement in the maximum lift coefficient. Most trailing edges exhibited an increase in the drag coefficient at a Reynolds number of 1.5 x 105. However, at a Reynolds number of 2.0 x 105, the drag coefficient showed a similar trend as the baseline. All types of trailing edges, including the baseline, displayed a similar trend in the pitching moment coefficient. When evaluating the lift coefficient to drag coefficient ratio, all trailing edges generally performed similarly at all Reynolds numbers. In general, the baseline model emerges as the optimal choice, showcasing superior aerodynamic characteristics across the evaluated parameters.

A finite element-inspired hypergraph neural network: Application to fluid dynamics simulations

A finite element-inspired hypergraph neural network: Application to fluid dynamics simulations

Aerodynamic and Aeroacoustic Effects of Different Transition Mechanisms on an Airfoil

The paper delves into the detailed sound generation and propagation mechanisms associated with tripping-induced flow perturbations and trailing-edge scattering using wall-resolved large-eddy simulations. Two distinct boundary-layer tripping techniques, namely a geometrically resolved stair strip and an artificially modeled trip using suction and blowing, are investigated. To facilitate comparison, the natural boundary-layer transition is also simulated as a baseline scenario. The analysis takes into account a Reynolds number of 4×105, a Mach number of 0.058, and a nonzero angle of attack of 6.25° over a NACA 0012 airfoil configuration. The mechanisms for sound generation and propagation related to trailing-edge noise remain consistent across the three transition scenarios. However, boundary-layer tripping notably leads to intricate, scenario-specific noise generation: there is an interaction between the laminar separation bubble and tripping for the stair strip case, whereas laminar boundary-layer instability is evident for the suction and blowing scenario. Aerodynamic flowfields involving acoustic noise sources, their propagating natures near the wall, and far-field acoustics are cross-examined in detail. The comprehensive analysis of observed phenomena provides valuable insights for understanding nonlinear flow and acoustic interactions relevant to airfoil noise and designing new types of trips under adverse pressure gradient flows.

Experimental Investigation of Low Reynolds Number Flow Around a Serrated NACA 0015 Airfoil

The study of low Reynolds number flows has triggered the interest of many researchers. This concern is attributed to the presence of various vortex structures that significantly affect aerodynamic performance. The study of such phenomena offers an opportunity to better understand and predict the behavior of fluid flows in three dimensions, leading to improved design strategies for aerodynamic systems. This study intends to examine the performance of different NACA 0015 airfoil configurations namely, baseline, serration, comb, comb-serration and poro-serrated, emphasizing on their influence on aerodynamic characteristics and flow structure. Experimental work is performed to provide valuable insights into the behavior of the flow field and the underlying physical phenomena. The current study has shown that the mean streamwise velocity of the serrated, combed, and comb-serrated configurations exhibit more stable flow patterns compared to the baseline airfoil. These patterns suggest a promising approach for delaying flow separation. In contrast, the poro-serrated model exhibited a more disordered flow pattern. Remarkably, when subjected to a 10-degree angle of attack, all the modified trailing-edge designs showcased minimal separation zones compared to the baseline configuration. At the same angle, the baseline's shear layer disintegrates, while the poro-serrated model displays increasing disturbance and separation. Conversely, the comb-serrated and serration models exhibit a smaller increase in unsteadiness. Furthermore, the study indicated that Musou black paint exhibits a higher rate of light absorption compared to flat black paint, but it demonstrates higher reflection levels on a poro-serrated surface. Collectively, the outcomes of this investigation hold significant implications for enhancing aerodynamic system designs.

High-density controlled environment agriculture (CEA-HD) air distribution optimization using computational fluid dynamics (CFD)

In this paper, the indoor environment of a small-scale high-density controlled environment agriculture (CEA-HD) space was simulated using computational fluid dynamics. Spatial modelling of the indoor environment considering the influential phenomena (e.g. transpiration and photosynthesis) over the indoor temperature, relative humidity, carbon dioxide (CO2) concentration, and airflow velocity is still challenging. These indoor environment conditions were computed for a 3D model of a CEA-HD experimental space while simultaneously modelling crop airflow impingement, transpiration and photosynthesis. The crops being grown were represented in the model as porous media zones and their exchanges with the indoor air were modelled using user defined functions. The air distribution parameters and configuration were optimized using a simplified 2D model to overcome the steep computational time, and associated cost, of 3D simulation. The objective function of the optimization problem relied on a correlation analysis of the simulation output. The optimization of the 2D model yielded an airfoil configuration that reduced the mean airflow speed and relative humidity variations between the cultivation tiers while achieving higher mean velocities (≈1.9 m·s−1) at a lower inlet speed (8 m·s−1). The proposed modelling and optimization approach is a small step forward towards model-based design and operation of CEA-HD production spaces.

Aerodynamic Analysis of a Logistics UAV with Foldable Bi-wing Configuration

Herein, a twin-boom, inverted V-tailed unmanned aerial vehicle (UAV) featuring a foldable bi-wing configuration is proposed for logistics and transportation applications. We employed the Navier–Stokes solver to numerically simulate steady, incompressible flow conditions. By examining the effects of key design parameters on aerodynamic characteristics and bypass flow fields in a two-dimensional state, we were able to suggest a more optimized foldable wing design. Building on the two-dimensional analysis, we performed aerodynamic assessments of the three-dimensional aircraft geometry. Our results indicated that appropriate wing and gap parameters can significantly enhance lift characteristics, maintaining high lift even during large-angle flights. Specifically, when compared to a mono-wing, the lift coefficient of the bi-wing increased by 27.1% at a 14° angle of attack, demonstrating the effectiveness of our wing-and-gap design. Optimal aerodynamic performance was achieved when the gap distance equalled the chord length in both flow and vertical directions. Further, the right combination of airfoil configuration, wing axes angle, and wingspan can improve flow field aerodynamic characteristics, while also enhancing the wing’s stall capacity. The lift coefficient reached its maximum value at an angle of attack of 15°, which has the potential to reduce takeoff and landing distances, thereby enhancing the UAV’s overall safety.

Investigation on Thermal and Hydraulic Performances in a Printed Circuit Heat Exchanger with Airfoil and Vortex Generating Fins

In this study, the effects of fin configurations and layouts on thermal and hydraulic performances in a printed circuit heat exchangers with supercritical liquefied natural gas as the working fluid are numerically studied, and the overall heat transfer performance is evaluated by the thermal performance factor. Firstly, the effect of three different airfoil configurations, that is, NACA 0024, NACA 0024 with vortex generator, and NACA 0024 with curved vortex generator (CVG) is investigated. The comparative results indicate that NACA 0024 and CVG combined configurations offer the best overall heat transfer performance. Furthermore, the effect of the CVG minimum transverse distance is analyzed in detail. The results show that for a given CVG configuration, the CVG minimum transverse distance should not be too small or too large, so that the longitudinal vortices (LVs) generated will not interact with each other and the LVs’ influences may reach a longer distance. The optimal CVG minimum transverse distance is 1.75 of maximum airfoil thickness. Finally, the effect of CVG attack angle is studied. The results indicate that the optimal CVG attack angle of combined configurations is 45° for improving the overall heat transfer performance, and an optimal CVG and airfoil fin arrangement is suggested.

Integrated Numerical Investigation on the Aerodynamics Characteristic and Vortex Development of Airfoil using Spalart-Allmaras Model

In this paper, the numerical simulation successfully obtained good results in analyzing fluid flow over the airfoil. Detailed explanations of simulation steps were also presented. The flow characteristics over three airfoil models were numerically simulated in this work: NACA0021, NACA2409, NACA2409+Fowler flap. The reliable Spalart-Allmaras (S-A) turbulent model was used and validated using reported data from experimental in terms of lift and drag coefficients. In this regard, the discrepancies of less than 10% were obtained for both coefficients, respectively. The boundary layer separation, vortex development, and air separation were clearly captured. The results of symmetric airfoil showed that the vortex shedding regimes occurred at α = 8o, and the stall critical-angle was about 14o. The value was higher for the NACA2409, where the airflow exhibited a relatively more stable behavior. Moreover, it is evident that flap addition altered lift-drag characteristics. The value of the lift-to-drag ratio increased due to the increase of Cl and the reduction of Cd. The parametric study was done on the α and flap deflection angle to attain the desirable airfoil configuration. The maximum result of airfoil configuration was obtained on the NACA2409 at α = 12o with 100 flap deflection angle while it enhanced the lift coefficient by about 54%. This result strengthens the robustness of the S-A turbulence model and projects the use of the S-A model for dealing with the aerodynamics analysis. This study is beneficial for initial aircraft design on the aerodynamics aspect of a wing.

Identification of anomalies in microphone array measurements of trailing edge noise by eigenstructure analysis.

An eigenstructure analysis is used to identify anomalies in large acoustic array measurements of airfoil trailing edge noise. Cross-spectra of 102 microphones distributed in a spiral configuration were inspected considering a range of inflow conditions and airfoil configurations. A measurement expectation is set by repeat measurements of non-anomalous data and is used for the analysis of additional data. This method is based solely on the comparison between the eigenstructure of cross-spectral matrices and can be used to efficiently inspect data for anomalies without having to beamform, as is conventional. Thus, processing and reviewing beamform maps can be relegated to post-processing after the experiment when more time is available.

Fluid-Structure Interactions and Aeroacoustic coupling of Airfoil with Flexible Membrane(s)

In this paper, fluid-structure interactions of a NACA 0012 airfoil mounted with short flexible membrane(s) and its coupling effect on airfoil aeroacoustics are presented. A time-domain direct aeroacoustic simulation coupled with structural dynamics is carried out at a low Reynolds number of 50,000 to explore the aeroacoustic-structural interactions. Two different airfoil configurations based on single and dual membranes are analyzed. The membrane deflections and their impact on the flow field are characterized in wavenumber-frequency domain to analyze the structural dynamics due to flow unsteadiness within the laminar boundary layer and the resulting acoustic waves emanating from the airfoil trailing edge. A strong correlation between the membrane displacement and downstream propagating flow is observed for all configurations whereas the correlation is considerably weakened between the membrane displacement and upstream acoustic waves which ultimately results in the airfoil self-noise reduction without affecting the airfoil aerodynamics. The extent of noise reduction for dual membrane airfoil configuration is observed to be considerably higher than the single membrane airfoil configuration which corresponds to a much lower correlation among the upstream propagating acoustic waves and membrane deflection for both the membranes and redistribution of upstream flow energy into different frequencies.

Aeroacoustic airfoil shape optimization enhanced by autoencoders

Aeroacoustic airfoil shape optimization enhanced by autoencoders

Adverse effect of rainfall on aerodynamic characteristics for different NACA airfoil configurations—A comprehensive review

Adverse effect of rainfall on aerodynamic characteristics for different NACA airfoil configurations—A comprehensive review