Data-driven surrogate aerodynamic prediction model and lift optimization for the flapping wing rotor

Purpose This work is devoted to validating a proposed finite element method with an immersed boundary technique for dealing with fluid-structure problems. Particularly, this study aims to investigate the vortex-induced vibration in pitching mode for flow past a cylinder with a NACA0012 cross-section at Re = 1000. Design/methodology/approach The numerical technique for solving fluid−structure interaction problems is described in the framework of a fixed-mesh finite element method. The solid motion is computed via the momentum equation for rotations. The solid velocity is imposed on the fluid as a restriction on the current fluid−solid immersed interface via a penalty technique. An exhaustive validation is first made by comparing the computed boundary layers and hydrodynamic coefficients (drag, lift, pressure and friction coefficients) on fixed cylinders with other numerical techniques. After that, the induced pitching problem is studied. Findings The analysis provides valuable information on the resulting fluid−structure interactions and the system’s stability. The results highlight the emergence of vortex shedding and its interaction with the structure, along with the role of aerodynamic damping in shaping the dynamic behavior. The findings consolidate the use of the proposed technique for the problem studied. Originality/value The novel aspects of this study encompass: the implemented immersed boundary formulation for rotational motion; the detailed evaluation of hydrodynamic coefficients and boundary layer evolutions; the evaluation of system stability under pitch response by varying mass ratios and torsional stiffness; and the provided exhaustive comparison with other numerical methods.

Study on the dynamics of maglev vehicle with viscoelastic suspension under the influence of aerodynamic lift and nonlinear electromagnetic force

This study investigates abnormal oscillations of high-speed pantographs in tunnels using the Improved Delayed Detached Eddy Simulation (IDDES) method and overset grid technology, analyzing aerodynamic forces, flow patterns, and spectral characteristics under different train speeds and tunnel cross-sectional areas. The results show that the aerodynamic behaviour of the pantograph can be divided into three stages: open air, transition section and tunnel. In tunnels, the time-averaged value and fluctuation intensity of the aerodynamic force coefficient are higher than in open air, with the disparity increasing as train speed and tunnel blockage ratio rise. In the transition section, the train and pantograph entering the tunnel generate pressure waves, which lead to significant fluctuations in the aerodynamic force of the pantograph. The dominant frequency of the aerodynamic force varies depending on the train speed, tunnel cross-sectional area, and track type. Different from the dominant frequency of 134 Hz observed in the open air, the power spectral density of aerodynamic drag and lift in the tunnel presents multiple harmonic peaks. The fundamental frequency shows a positive correlation with both train speed and tunnel blockage ratio, increasing as train speed rises and tunnel cross-sectional area decreases. The coupling of complex vortices will increase the instability of the flow field, affect the dynamic response of the pantograph, and may induce oscillation.

The aerodynamic design of wind turbine blades plays a decisive role in energy capture, structural loading and overall cost of wind energy, yet conventional design workflows remain heavily reliant on Blade Element Momentum (BEM) theory and high-fidelity computational fluid dynamics (CFD). As rotor sizes and design requirements become more demanding, these physics-based tools make high-dimensional, multi-objective optimization increasingly expensive. Over roughly the last five years, machine learning (ML) has emerged as a promising way to alleviate these limitations by providing fast, flexible surrogates and new forms of inverse and data-driven design. This review summarizes recent progress in machine-learning-based aerodynamic optimization of wind turbine blades, with a particular emphasis on wind-turbine-specific airfoils. We first recall the fundamentals of blade aerodynamics and the structure of conventional BEM/CFD-based optimization workflows. We then discuss the main classes of ML frameworks used in this context, and review their concrete applications to airfoil-level modeling and design, focusing on surrogate models for predicting lift and drag coefficients and surrogate-assisted optimization of airfoil shapes. These airfoil-level surrogates are highlighted as reducing the caculation cost and improving the optimization efficiency compared with the single-fidelity surrogate model. The review concludes by outlining key challenges, including data quality, generalization, physics consistency and multidisciplinary integration, and by identifying promising research directions towards physics-informed, uncertainty-aware and multi-fidelity ML frameworks for the aerodynamic design of next-generation wind turbine blades.

Transonic shock buffet, characterized by large-amplitude self-sustained shock oscillations arising from shock wave/boundary layer interactions, poses significant challenges to aircraft handling quality and structural integrity. Conventional control strategies for buffet suppression typically require prior knowledge of unstable steady-state solutions or time-averaged flow fields and are only applicable to fixed-flow conditions, rendering them inadequate for realistic flight scenarios involving time-varying parameters. This study proposes a data-driven adaptive control framework for transonic buffet suppression utilizing localized morphing skin as the actuation mechanism. The control system employs a Multi-Layer Perceptron neural network that dynamically adjusts the local skin height based on lift coefficient feedback, with the target lift coefficient determined through a moving average method. Numerical simulations on the NACA0012 airfoil demonstrate that the optimal actuator configuration—a skin length of 0.2c with maximum deformation positioned at 0.65c—achieves effective buffet suppression with minimal settling time. Beyond this baseline case, the proposed method exhibits robust performance across different flow conditions. Furthermore, the controller successfully suppresses buffet under time-varying flow conditions, including simultaneous variations in Mach number and angle of attack. These results demonstrate the potential of the proposed framework for practical aerospace applications.

In the present study, an examination of the aerodynamic characteristics in tandem airfoil systems experiencing ground effect was performed. The research was carried out using Computational Fluid Dynamics (CFD) analyses. The effects of multiple parameters, such as angle of attack (AOA) at 0°, 4°, and 8°, horizontal distance between the front and rear airfoils (d/c), proximity to the ground (h/c) and Reynolds number on lift (CL), drag (CD), and moment (Cm) coefficients were investigated. The best aerodynamic performance (maximum CL/CD) was achieved at a 4° AOA, very close to the ground (h/c=0.1), in the range of 1≤d/c≤2 and higher Reynolds number. It was also determined that the 0° AOA exhibited a distinctly different behavior from the other angles (4° and 8°), as decreasing ground clearance led to a reduction in CL at 0°, whereas it caused an increase at 4° and 8°.

In order to effectively reveal the nonlinear characteristics of a dish concentrating solar thermal power system (DCSTPS) under pulsating wind-induced loads, a fluid simulation model of the DCSTPS was established, and the simulated pulsating winds were developed via the user-defined function (UDF) combined with the autoregressive (AR) model using MATLAB (R2015b). And based on the fluid simulation calculations of the DCSTPS, the time-range data of the relevant wind vibration coefficients under different working conditions were obtained. The research results show the following: (1) When the altitude angle α is 0° or 180° due to the azimuth angle β = 0°, the maximum values of their drag coefficient Cx, lateral force coefficient Cy, and lift coefficient Cz are similar, and the maximum of rolling moment coefficient CMx is significantly smaller than the values at the other two angles; the maximum of the pitch moment coefficient CMy and maximum of the azimuth moment coefficient CMz are significantly larger than the values of the other two angles. (2) The increase in altitude angle α leads to a reduction in the drag coefficient Cx, an increase in the lift force coefficient Cz, and an increase of the pitch moment CMx. Moreover, an improved phase space delay reconstruction method was developed to calculate the delay time, Lyapunov exponent, and Kolmogorov entropy of the DCSTPS, and the research results show that (1) the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS are greater than zero under the action of pulsating wind; (2) the action of pulsating wind will cause increases in the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS and will accelerate the divergence speed of the DCSTPS trajectory; and (3) the time for the DCSTPS to enter the chaotic state will be shortened, while the time of entering a chaotic state and degree of subsequent chaotic states will be significantly affected by relevant wind vibration coefficients but without regularity.

Strong crosswinds and train–tunnel aerodynamic interactions cause the aerodynamic loads acting on the train body to change more drastically when a high-speed maglev train enters a tunnel. This greatly raises the risk of safety incidents like derailment or overturning. This study employs the FLUENT 2023 R2 computational fluid dynamics simulation software with an overset grid method to numerically investigate the influence patterns of crosswinds on aerodynamic loads and relevant safety issues for a 600 km/h maglev train entering tunnels under various crosswind conditions. The findings show that (1) the marshaling location has a strong correlation with aerodynamic performance. When there is no crosswind, the head vehicle (HV) has the greatest chance of flipping, while the rear vehicle (RV) has the worst lift characteristics. All three vehicles experience significant sudden changes in lateral force coefficients prior to tunnel entry, indicating considerable derailment risks. (2) Aerodynamic loads on the HV show significantly greater sensitivity to crosswind velocity variations compared to the middle vehicle (MV) and RV, with the amplitude reduction in lateral forces in the HV showing approximately linear increase with wind speed. (3) A 50 km/h reduction in train speed decreases the amplitude of change in the lift coefficient and lateral force coefficient by approximately 4.8% and 8.9%, respectively, and the peak overturning moment in open air and tunnel by approximately 11.4% and 15.7%, respectively. These discoveries have both practical value for advancing high-speed maglev networks and theoretical significance for enhancing the safety and reliability of Chinese maglev systems.

This study presents a numerical analysis of airfoil aerodynamic characteristics at low angles of attack using a structured multizone meshing approach. The computational model was developed in ANSYS Workbench, with simulations conducted using ANSYS Fluent on a two-dimensional airfoil enclosed within a far-field domain. The mesh configuration consists of approximately 540,000 elements and 541,000 nodes, achieving a maximum skewness below 0.26, which indicates high mesh quality and numerical stability. Steady-state simulations were performed for angles of attack of −5°, 0°, 5°, and 10° to evaluate lift and drag behaviour, as well as pressure and velocity distributions around the airfoil surface. The numerical results show a consistent increase in lift coefficient with increasing angle of attack, accompanied by a corresponding rise in drag coefficient. At moderate angles of attack, particularly around 5°, the airfoil demonstrates an optimal aerodynamic performance with a favourable lift-to-drag ratio. These findings highlight the capability of structured multizone meshing to accurately capture key aerodynamic trends while maintaining computational efficiency. The results confirm that this meshing strategy is suitable for preliminary aerodynamic analysis and early-stage design of airfoil-based applications, such as small-scale wind turbine blades operating under low to moderate inflow conditions

This work concentrates on the effect of a flex-skin trailing edge flap on the aerodynamic characteristics of SD7037 airfoil at low Reynolds numbers, in the range of 2·10 5 to 5·10 5 using computational methods. The study used a range of angle of attack (AOA) associated with the take-off phase and different flap angles. The numerical model was set up in Siemens STAR-CCM+ package using the κ-ω shear stress transport turbulence model and the (γ-Reθ) transition model which ensured the approximate solution of Navier-Stokes equations. The verification of the computational solution was done by the comparison with the available experimental data of the plain flap, and it was discovered that the results matched pretty well at lower AoAs. Results indicated that certain sets of AoAs and flap angles can notably achieve the lift over the drag ratio above the baseline conditions, thus improved the performance especially during take-off stage. Besides, some combinations were found to be inefficient, and these were recommended to be discarded. Additionally, the results showed that the flex-skin flap generated higher lift coefficient but also higher drag coefficient at the same range of AoAs as compared to that of the plain flap.

This study proposes an integrated design approach for a multifunctional UAV using composite materials, combining vacuum infusion, CFD-based aerodynamic analysis, and an STM32-based energy management system. CFD results showed a lift coefficient C L = 0.812, drag coefficient C D = 0.055, and L / D = 14.7, representing a 28 % improvement over aluminum structures. FEM analysis indicated a maximum stress of 312.4 MPa with a safety factor of 1.12, while vacuum infusion achieved 98.7 % resin impregnation, enhancing stiffness by 28 % and reducing weight by 25 %. The automated energy management system increased energy efficiency by 16.3 %, extending flight duration and improving operational stability.

This research examines the aerodynamic performance of three UAV wing configurations base wing, Model A with cambered wingslots, and Model B with symmetrical wingslots at low Reynolds numbers. Using CFD simulations in ANSYS FLUENT, key parameters such as lift coefficient, drag coefficient, induced drag, and lift-to-drag ratio were analysed across angles of attack from 0° to 15° and flight velocities of 8 m/s, 10 m/s, and 12 m/s. Results reveal that wing slots enhance aerodynamic efficiency by 12.5% at low angles of attack. Model A with cambered wingslots excels in pre-stall lift generation, while Model B with symmetrical wingslots achieves lower drag at lower angles. Both configu-rations significantly reduce induced drag by up to 29% during cruise conditions, highlighting their effectiveness in im-proving UAV performance.

Abstract The electrohydrodynamic force of a surface dielectric barrier discharge (SDBD) has been well-developed for flow control applications during recent decades. In the present paper, a geometrical modification of the SDBD plasma actuator has been applied to induce a vectorised normal flow at the trailing edge of a NACA0015 aerofoil. The pitot-tube velocity measurements of the normal jet along its propagation direction revealed formation of vortices at the centre of the electrode distance played a role in flow control authority of the jet. The aerodynamic operation of the double-SDBD structure as a virtual flap was assessed versus a single counter-flow jet of a floating structure at pre- and post-stall angles of attack at low Reynolds numbers. It was found that at small angles of attack, the steady counter-flow gives the most effectiveness of lift enhancement in low velocity, whereas in the higher velocity the unsteady one results in more efficacy. The efficiency of both steady and unsteady normal jets increased considerably at high angles such that a lift coefficient improvement of 38% was achieved at $\alpha = 14^\circ $ . In the higher velocity, the plasma induced vertical flow acts like a Gurney flap, causing lift increase at high angles by affecting the vortical structures at the trailing edge. Evaluating the obtained results recommended employment of the induced normal flow as a virtual flap at high angles of attack in the unsteady actuation mode.

A wind turbine's blade section is essential for capturing wind energy and producing clean, renewable energy. Every turbine blade is meticulously crafted with certain aerodynamic concepts in mind, with a primary emphasis on lift and drag forces. Optimizing energy capture and guaranteeing the overall efficiency of wind power systems require an understanding of the complexities of aerodynamics in this context. Using numerical simulations carried out with Ansys Fluent software, the current study examines the aerodynamics of three airfoils—NACA-4412, NACA-23012, and NACA-63415—with an emphasis on airflow patterns and performance. The computational method comprehensively investigates the effects of rotational speeds (from 2 to 16 degrees per second) and a variety of Reynolds numbers (from 1.25e6 to 2e6) using two-dimensional unsteady simulations. The results show how operational parameters and airflow patterns interact dynamically. variations in velocity magnitude were detected, affected by rotational speeds and Reynolds numbers. These fluctuations gave further insights into flow behavior around the airfoil, such as the discovery of flow separation zones represented by velocity vectors. Analysis of lift coefficient values showed little variance concerning changes in rotational speed, indicating that 8 degrees per second is a suitable rotational speed for the cases under study. The values of the drag coefficient increased over time, with the NACA-63415 aerofoil showing the highest values. Conversely, lift coefficient values showed a rising fluctuation that peaked at a certain value before trending downward. Notably, when compared to the other aerofoils under study, the NACA 4412 aerofoil showed better aerodynamic coefficients.

This paper mainly studies the influence of adhering hidden movable airflow guide strips to the surface of horizontalaxis wind turbine blades on the aerodynamic performance of the blades. The experimental data suggest that the guide strip changes the flow direction of the airflow. A reverse force will be generated in the opposite direction of the airflow outflow, i.e., the blade guide strip's resistance and the airflow's flow distance on the blade surface will be increased. The lift of the blade will be increased with a low starting wind speed and a significant wind energy utilization effect. The research results show that the guide strip structure can increase the lift coefficient of the blade by 9.1% under the condition of a small Angle of attack. When the wind speed reaches 8 m/s, the power coefficient increases by 14.1% and the starting wind speed decreases by 0.5 m/s. However, the negative resistance of the guide strip was increased at high incoming flow speeds. At this time, the guide strip was adopted to level the actuator and placed on the blade's surface. The experimental results show that when the guide strip is retracted, the output power of the wind turbine is the same as that of the prototype blade.Therefore, the guide strip blades with retraction and extension functions enhance the low-speed performance of the wind turbine while maintaining its high-speed performance.

We present experimental and numerical studies aimed at improving models of animal flight at moderate Reynolds numbers ( - ). Quasi-steady aerodynamic force and moment data were collected using a rectangular wing across various angles of attack, . The drag coefficient, , is well described by a simple trigonometric function, while the lift coefficient, , combines trigonometric and exponential terms-the latter capturing the linear behavior at small predicted by inviscid theory. We also derive an empirical relation for the center of pressure as a function of , allowing evaluation of the pitching moment coefficient, , about any axis. These formulas are integrated into a dynamic flapping wing model to simulate forward flight of a pigeon and a bat at different speeds. Compared to prior models, our approach yields better agreement with wingbeat frequency data, particularly at high speeds. The small angle regime proves especially beneficial, offering higher , which translates to reduced power demands and smaller body pitch variation-key considerations for the design of flapping wingrobots.

Abstract The Vertical Take-Off and Landing (VTOL) aircraft exhibit complex and rapidly varying dynamics during the transition flight phase, which poses significant challenges for accurate modeling and aerodynamic parameter estimation. This paper presents a parameter estimation framework to identify unknown aerodynamic coefficients governing the transition flight, leveraging experimental flight data of a tilt-rotor VTOL UAV in outdoor experiments. The VTOL UAV has a hybrid configuration with two tilting rotors, two static rotors, and fixed wings. A nonlinear dynamic model describing the longitudinal motion is developed and reformulated into a regression structure suitable for parameter estimation. A projection-based constrained Recursive Least Squares (RLS) algorithm is then applied to estimate critical aerodynamic parameters, including lift, drag, and thrust coefficients, under physical constraints. The convergence and accuracy of estimation algorithm for time-varying coefficients is firstly verified by simulation. The parameter estimation is further validated by six experimental flight tests with different tilting rates of 12 deg/s and 14 deg/s. Experimental results demonstrate the accurate estimation by accurate predictions of the aircraft states υx, υz, ωy with RMSEs of 0.7230 m/s, 0.0990 m/s, and 0.0508 rad/s, respectively.

The development of solar-powered UAVs offers major advantages, such as extended mission autonomy, marking a significant technological advance in the aerospace industry. In this context, the study demonstrated the feasibility of additive manufacturing of a solar-powered UAV by successfully completing all the steps necessary for the development of an aeronautical product. The conceptual design was the initial phase in which the needs were defined, and the basic vision of the UAV model was outlined, exploring multiple possible solutions to identify the concept capable of meeting the mission requirements (search and rescue and surveillance). The preliminary design stage included aerodynamic analysis of the aircraft and preliminary sizing of the propulsion system and solar cells. The preliminary design stage included aerodynamic analysis of the UAV model, resulting in a lift coefficient of 1.05 and a drag coefficient of 0.08 at an angle of attack of 15°. A major advantage of the design is the integration of the electrical circuit, where solar input reduced battery consumption from 92.5 W to just 40.4 W in standard operational conditions, thereby more than doubling the UAV’s autonomy (from 48 min to approximately 110 min). The detailed design stage consisted of the final design of the solar UAV model for additive manufacturing, after which the final electrical architecture of the energy system was established. The model was subsequently validated by a finite element analysis, which confirmed the strength of the wing structure by achieving a safety factor of 6.6. The use of additive manufacturing allowed the rapid and accurate production of the structural components of the UAV model, ensuring that their subsequent physical assembly would be straightforward.

ABSTRACT Engineering problems often comprise free‐surface flows in turbulent regime. Lagrangian mesh‐free particle‐based methods are well suited for the simulation of flows involving complex free‐surface deformation. However, the analysis of turbulent modeling for particle‐based methods is relatively scarce in the literature. In this work, an analysis of a hybrid RANS‐LES turbulence model adapted for the Moving Particle Semi‐implicit (MPS) method is performed. In the turbulence model, a zero‐equation RANS is applied near the wall boundaries and a standard Smagorinsky LES model is applied elsewhere. Given that the eddy viscosity of the turbulent modeling depends on the distance between the fluid and the nearest wall particle, the calculation of the fluid‐wall particle distance may demand a high computational cost due to undefined topology among moving particles. In this way, a method based on the cell‐linked list is proposed to improve the nearest wall search for the turbulence model. The implementation is verified through simulation of a lid‐driven flow with Reynolds number between and . The result shows that despite the overhead when the turbulence model is adopted, the time needed to reach steady state is shortened so that the overall computational costs are almost the same. In addition, the improvement due to the adoption of turbulence model is more evident for the highest Reynolds numbers. As an application, the flow around a submerged square cylinder near the surface with Reynolds number of is simulated. The influences of the cylinder submergence depths on the drag and lift coefficients are investigated for a range of depth‐to‐length ratios between and . When the turbulence model is applied, a smoother convergence tendency is obtained as the resolution increases. Moreover, the flow around the square cylinder is better represented, resulting in more regular vortex shedding. Different flow behaviors were identified around the square cylinder as the submergence depth changes.