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High-speed maglev trains represent a key direction for the future development of rail transportation. As operating speeds increase, they face increasingly severe aerodynamic challenges. The streamlined aerodynamic shape of a maglev train is a critical factor influencing its aerodynamic performance, and optimizing its length plays a significant role in improving the overall aerodynamic characteristics of the train. In this study, a numerical simulation model of a high-speed maglev train was established based on computational fluid dynamics (CFD) to investigate the effects of streamline length on the aerodynamic performance of the train operating on an open track. The results show that the length of the streamlined section has a pronounced impact on aerodynamic performance. When the streamline length increases from 8.3 to 14.3 m, the aerodynamic drag of the head and tail cars decreases by 16.2% and 32.1%, respectively, with reductions observed in both frictions drag and pressure drag—the latter showing the most significant decrease in the tail car. Moreover, the extended streamline length effectively suppresses flow separation on the train body surface. The intensity of the positive pressure region on the upper surface of the head car streamlined section is reduced, directly leading to a 38.2% reduction in lift. This research provides a theoretical basis for the parametric design of aerodynamic shapes for high-speed maglev trains and offers guidance and recommendations for drag and lift reduction optimization.

A numerical study on supersonic cavity flow is carried out, where the influence law of the freestream parameters and configuration factors on static aerodynamic characteristics is investigated, focusing on the change of pressure distribution on the cavity walls at high and low Mach numbers. It is found that with the Mach number increment at high speeds (M>2), the pressure peak on the rear side of the cavity bottom floor rises, and the change in pressure distribution on the cavity walls shows a variating trend in flow type from a closed-cavity flow to an open-cavity flow, which is consistent with the law at low speeds (M≤2). At high speeds, the change in Reynolds number has a certain impact on the pressure distribution in the cavity, which is inconsistent with the law at low speeds. The increase of Reynolds number will increase the pressure on the rear side of the cavity bottom floor and on the rear wall, and the greater the Mach number, the greater the difference caused by Reynolds number variation. When the length-to-depth ratio increases at high speeds, the pressure peak on the rear side of the cavity bottom floor decreases, and the flow type is changing from an open-cavity flow to a transitional-cavity flow, which is consistent with the law at low Mach numbers, while the pressure variation is greater at high speeds. The influence of the length-to-width ratio on the pressure distribution is relatively small, and the increase of length-to-width ratio increases the pressure peak on the rear side of the cavity bottom floor slightly. Spanwise bending has a certain impact on the pressure distribution. The pressure peak on rear side of the bottom floor increases when the cavity is bending, which is consistent with the influence caused by length-to-width ratio increment.

Multi-rotor ducted propellers, which integrate the high-efficiency characteristics of ducted propellers with the layout flexibility and safety advantages of distributed propulsion, are extensively utilized in the propulsion systems of low-altitude transport systems and large-scale unmanned aerial vehicles. This study numerically investigates the effects of spanwise distance, streamwise distance, rotational consistency, and rotational phase gap on the unsteady aerodynamic characteristics of multi-rotor ducted propellers under hovering conditions. A parameterized numerical computation model and an Aligned Rank Transform Analysis of Variance (ART-ANOVA) method suitable for small datasets exhibiting regular patterns were developed. Initially, numerical simulations investigated the aerodynamic performance of multi-rotor ducted propeller models with varying layout parameters. The aerodynamic coefficients of the propellers monotonically decrease as the layout spacing increases; however, the change trends differ. Aerodynamic interference reduces the airflow velocity and influences the distribution of high-pressure zones, consequently impacting thrust and efficiency. Subsequently, this paper examined the coupled effects of two rotational characteristics. The relationship between propeller aerodynamic performance and rotational phase gap exhibits distinct trigonometric function characteristics. The presence of the duct mitigates the mutual interference between blades, thereby altering the amplitude and phase of these characteristics. Finally, an ART-ANOVA method was employed to quantify the main and interaction effects, revealing that rotational consistency has a dominant influence on all aspects of aerodynamic performance. Insights into aerodynamic performance are crucial for advancing low-altitude transport systems that utilize ducted propeller propulsion systems.

There is high flight efficiency of flapping wing aircraft, and its hovering ability, wind loading rating, maneuverability and concealment are better than that of multi-rotor and fixed-wing aircraft. In this paper, the bionic flapping wing is taken as the research subject, and a complete motion process of the flapping wing is divided into four stages by numerical method under the condition of incoming flow. It is found that there is delayed stall mechanism of leading-edge vortex, wake vortex capture mechanism and rotating circulation mechanism in flapping wing flight. On this basis, the impact of flapping wing kinematic parameters on flapping wing aerodynamic characteristics is explored. The effects of different flapping motion parameters on flapping aerodynamic parameters are investigated from three perspectives, including flapping frequency, direction of flapping wing motion and trajectory of flapping wing. It is demonstrated that increasing the flapping frequency can result in an improvement in the lift resistance characteristics. The phase difference of flapping wing motion can affect the angle of attack state for airfoil during flapping. When the flapping frequency, amplitude, and phase difference are identical, there is minimal disparity in the lift characteristics among different trajectories. However, a substantial discrepancy arises in the drag coefficient. The axisymmetric of motion trajectory will also cause significant differences in the lift characteristics.

This article presents the main results of a detailed study of the flow around a 10 ° cone in different Mach number (M = 0.2–1.4), Reynolds number (Re = 2.1·10 6 –14.1·10 6 ), and perforation coefficient ( F  = 0–18%) ranges and at various angles of attack (− 14 ° – + 14 ° ). Experimental studies were carried out in the T-128 transonic wind tunnel at the Central Aerohydrodynamic Institute. A brief description of the aerodynamic setup and measuring equipment is given. During the tests, aerodynamic loads were measured using six-component internal strain-gauge balances simultaneously considering the distribution of static pressure along the test section walls, base pressure, non-stationary static pressure on the cone surface and the test section wall, as well as thermograms of the cone surface. A brief description of the Electronic Wind Tunnel software package is given, with the help of which the computational studies of the flow around a cone in a perforated test section were performed. The level of static pressure fluctuations in the model is shown to be lower than at the perforated walls. Combining thermal imaging tests with balance tests made it possible to explain the nonlinearity of the dependence of the lift coefficient on the angle of attack and to estimate the critical angles of attack at which symmetric and asymmetric flow separations on the side surface of the cone appear. The values obtained for the critical angles of attack agree with the calculated and experimental data of other authors.

The wing aerodynamic shape optimization is a typical high-dimensional problem with numerous independent design variables. Researching methods to reduce the dimensionality of optimization from the perspective of aerodynamic characteristics is necessary. One traditional aerodynamic-based approach decouples the wing’s camber and thickness according to the thin airfoil theory, but it has limitations due to unclear application scope and effectiveness. This paper proposes an improved approach that determines the values of certain thickness variables based on a data-driven aerodynamic characteristics model before optimization, which considers longitudinal stability. By reducing the number of design variables, the dimensionality of optimization is decreased effectively. The derivation of the improved approach is accomplished through the design of experiments, parametric modeling, computational fluid dynamics, and sensitivity analysis. The effectiveness of the improved approach is validated by applying it to the aerodynamic optimization of an ONERA-M6 wing in subsonic flow based on the surrogate-based optimization algorithm. The results demonstrate that the improved approach significantly accelerates the optimization process while maintaining global effectiveness.

The correlation between aerodynamic data obtained from ground and flight tests is crucial in developing aerospace vehicles. This paper proposes methods for modelling this correlation that combine feature extraction and symbolic regression. The neighborhood component analysis (NCA) method is utilized to extract features from the high-dimensional state space and then symbolic regression (SR) is applied to find the concise optimal expression. First, a simulation example of the NASA Twin Otter aircraft is used to validate the NCA and the SR tool developed by the research team in modeling the aerodynamic coefficient deviation between ground and flight due to an unpredictable inflight icing failure. Then, the method and tool are applied to real flight tests of two types of aerospace vehicles with different configurations. The final optimized mathematical models show that the two vehicles’ pitching moment coefficient deviations are related to the angle of attack (AOA) only. The mathematical model built using NCA and the SR tool demonstrates higher fitting accuracy and better generalization performance for flight test data than other typical data-driven methods. The mathematical model delivers a multi-fold enhancement in fitting accuracy over data-driven methods for all fight cases. For UAV flight test data, the average root mean square error (RMSE) of the mathematical model demonstrates a maximum improvement of 37% in accuracy compared to three data-driven methods. For XRLV flight test data, the prediction accuracy of the mathematical model shows an enhancement exceeding 80% relative to Gaussian kernel SVM and Gaussian process data-driven models. The research verifies the feasibility and effectiveness of the data feature extraction combined with the symbolic regression method in mining the correlation law between ground and flight deviations of aerodynamic characteristics. This study provides valuable insight for modeling problems with finite data samples and explicit physical meanings.

Purpose Unmanned aerial vehicles (UAV) with remote and/or automated flight and mission controls have replaced airplanes with pilots in many important roles. This study aims to deal with computational fluid dynamics (CFD) analysis and development of the aerodynamic configuration of a multi-purpose UAV for low and medium altitudes. The main aerodynamic requirement was the application of the tandem wing (TW) concept, where both wings generate a positive lift and act as primary lifting devices. Design/methodology/approach Initial design analyses of the UAV’s aerodynamic configuration were performed using ANSYS Fluent. In previous work in Fluent, the authors established a calculation model that has been verified by experiments and, with minor adjustments, could be applied for subsonic, transonic and supersonic flow analyses. Findings The design evolved through eight development configurations, where the latest V8 satisfied all the posted longitudinal aerodynamic requirements. Both wings generate a substantial amount of positive lift, whereas the initial stall occurs first on the front wing, generating a natural nose-down stall recovery tendency. In the cruising flight regime, this configuration has the desired range of longitudinal static stability and its centre of pressure is in close proximity to the centre of gravity. Practical implications The intermediate development version V8 with proper longitudinal aerodynamic characteristics presents a good starting point for future development steps that will involve the optimization of lateral-directional aerodynamics. Originality/value Using contemporary CFD tools, a novel and original TW aerodynamic configuration have evolved within eight development stages, not being based on or derived from any existing designs.

Investigating the role of leading edge tubercles on the aerodynamic behavior of S823 airfoil tailored for wind turbine applications has been the forefront of the study. The aerodynamic characteristics of S823 airfoil effectuated by leading edge tubercles are ascertained at Reynolds number Re=200000 which is the usual operating range of most of the small-scale wind turbines. Firstly, the study elucidates the numerical investigation of baseline airfoil and later modified airfoils exhibiting different amplitude A and wavelength λ of the sinusoidal leading edge tubercles represented as A07W50, A12W50, and A07W25. The aerodynamic characteristics of the airfoils at Re=200000 and angles-of-attack ranging from 00 to 200 are evaluated numerically through k-ω SST turbulence model using ANSYS FLUENT® software package. A preliminary comparison of the computational data shows that the coefficient of lift Cl of all the modified airfoils was visibly superior to the baseline model across the angles tested. A07W50, A12W50 and A07W25 registered 20.6%, 26.2%, and 8.7% increase in the Cl values as compared to the baseline model. Contrasting to the Cl values, the aerodynamic efficiency Cl/Cd of the baseline model was slightly better but only across the pre-stall regime and later culminated with a sudden hard stall. Promisingly, this type of hard stall was not true for the tubercled models that demonstrated a more gradual and restrained stalling characteristic, thus showcasing superior performance in the post stall envelope that was never observed for the baseline model. Based on the outcomes, A07W50 model that displayed better aerodynamic characteristics was eventually fabricated and experimentally tested for its performance in a low speed wind tunnel. The numerical results of A07W50 were in good agreement with the experimental results. The overall results of the study prove beyond any point of doubt that tubercles indeed aid in improving the aerodynamic characteristics by enhancing the lift Coefficient Cl, rendering soft stalling nature and extending the scope of operation for the airfoil under study. Finally, the study positively confirms that leading edge tubercles very much play a significant role in passively augmenting the fluid dynamic characteristics of S823 airfoil and also qualify them to be a competitive passive flow control device.

Appropriate modeling of unsteady aerodynamic characteristics is required for the study of aircraft dynamics and stability analysis, especially at higher angles of attack. The article presents an example of using artificial neural networks to model such characteristics. The effectiveness of this approach was demonstrated on the example of a strake-wing micro aerial vehicle. The neural model of unsteady aerodynamic characteristics was identified from the dynamic test cycles conducted in a water tunnel. The aerodynamic coefficients were modeled as a function of the flow parameters. The article presents neural models of longitudinal aerodynamic coefficients: lift and pitching moment as functions of angles of attack and reduced frequency. The modeled and trained aerodynamic coefficients show good consistency. This method manifests great potential in the construction of aerodynamic models for flight simulation purposes