Aerodynamic Characteristics Research Articles

Airfoil aerodynamic/stealth design based on conditional generative adversarial networks

Aerodynamic/stealth design is becoming an important factor in the advanced airfoil design. In this work, a supervised machine learning method is proposed for aerodynamic and stealth integrated airfoil design. The conditional generative adversarial network (CGAN) is constructed for the multidisciplinary design of airfoil. Then, the generator and discriminator simply using deep neural network have good robustness and stability in training. The CGAN model also shows good generalization capability in the test set, with less than 1% error in fitting to the airfoil profile data, and the generated airfoils are within 10% error compared to the test airfoil aerodynamic stealth characteristics. In addition, the optimization results based on the CGAN model demonstrate that aerodynamic performance improvement would increase the airfoil camber and stealth performance improvement would sharpen the airfoil leading edge.

Impact of free-stream orientation and thermal buoyancy on aerodynamic and heat transfer characteristics in mixed convective flow past an elliptical cylinder

Impact of free-stream orientation and thermal buoyancy on aerodynamic and heat transfer characteristics in mixed convective flow past an elliptical cylinder

Influence of geometric parameters on aerodynamic characteristics of serpentine convergent-divergent nozzle

The serpentine convergent-divergent nozzle represents an optimal configuration for next-generation fighter aircraft characterized by low detectability and high thrust-to-weight ratio. In contrast to the serpentine convergent nozzle, such configuration offers increased design flexibility with additional parameters, leading to heightened interactions among these parameters. As such, it is crucial to reveal the influence of design parameters on the aerodynamic performance of the serpentine convergent-divergent nozzle and the multifactor interaction, as well as its mechanism. Therefore, the influence, interaction and sensitivity of parameters on the aerodynamic performance of the nozzle were numerically investigated using the orthogonal test method. Additionally, the influence mechanism of the convergence angle, throat aspect ratio, and axial length to inlet diameter on the flow characteristics of the nozzle was investigated in detail. The results show that the convergence angle is identified as the main factor affecting the aerodynamic parameters of the nozzle. As the convergence angle increases, the thrust coefficient, total pressure recovery coefficient and discharge coefficient gradually decrease. The interaction between throat aspect ratio and other parameters is obvious. Different design parameters affect the local loss and the friction loss by affecting the curvature and wetted perimeter area, resulting in different aerodynamic characteristics of serpentine convergent-divergent nozzle.

Modeling two-dimensional ice shape based on fractal interpolation

The ice accretion data obtained from ice wind tunnel tests reveal a multiscale structure and rough surface. In the follow-up aerodynamic evaluation of icing airfoils, simplified two-dimensional ice shapes are generally used as substitutes, but this simplification changes the aerodynamic effects of the original ice shape. Therefore, finding a simple and effective two-dimensional ice shape simulation method is urgent. Due to the self-similarity characteristics of ice shape surfaces, fractal interpolation is proposed for ice shape simulation. First, the geometric characteristics of the ice shapes are analyzed to determine interpolation points, and an iterative function system is constructed for interpolation simulation. Considering the influence of various characteristics of ice shapes on aerodynamics, interpolation parameters are limited to simulating more realistic ice shapes. High-order numerical simulation methods were utilized to numerically simulate and analyze the aerodynamic characteristics of icing airfoil while also verifying the feasibility of fractal interpolation for simulating ice shapes. The analysis revealed that this method could effectively simulate ice profiles of various feature scales with minimal ice shape data. These simulated shapes closely resemble real ice formations and maintain the original aerodynamic characteristics of the icing airfoil. This method can be used to improve the computational accuracy of ice accretion codes and provide improvement strategies for complex ice shape prediction; thus, this method has great application prospects in engineering.

Influence of flow interactions on the aerodynamic characteristics of tandem self-propelled flapping wings with a nonzero angle of attack

It is common in nature for birds or insects to fly in flocks. This study sought to understand the interaction mechanism between complex flows and the aerodynamic characteristics of flocks of flying organisms by employing the lattice-Boltzmann method to investigate tandem self-propelled flapping wings with an angle of attack of 10°. The effects of the initial heaving phase, the initial spacing between the fore and hind wings, and the phase difference between the heaving motions of the fore and hind wings were investigated. It was found that when the fore and hind wings flap in phase, the initial heaving phase and initial spacing can influence the final locomotive state of the tandem system, resulting in three modes: stable flight, collision, and separation. When the tandem system eventually achieves stable flight, only one equilibrium state is observed. In this equilibrium state, the trailing-edge vortex generated by the fore wing reattaches to the lower surface of the hind wing, resulting in 82.3% lower lift efficiency but 19.9% higher propulsive efficiency when compared to a single wing. When the fore and hind wings flap nearly out of phase, the tandem system has better lift characteristics while maintaining good propulsive performance. These findings improve the understanding of the principles of lift and thrust generation in flock flight and will help guide the design of bionic micro air vehicles.

Multiple boundary layer suction slots technique for performance improvement of vertical-axis wind turbines: Conceptual design and parametric analysis

Vertical-axis wind turbines (VAWTs) are gaining attention for urban and offshore applications. However, their development is hindered by suboptimal power performance, primarily attributable to the complex aerodynamic characteristics of the blades. Flow control techniques are expected to regulate the flow on the blade surface and improve blade aerodynamics. In the present study, an effective active flow control technique, multiple boundary layer suction slots (MBLSS), is designed for VAWTs performance improvement. The impact of MBLSS on the aerodynamic performance of VAWTs is examined using high-fidelity computational fluid dynamics simulations. The response surface methodology is employed to identify the relatively optimal configuration of MBLSS. Three key parameters are considered, i.e., number of slots (n), distance between slots (d), and slot length (l), which vary from 2 to 4, 0.025c to 0.125c, and 0.025c to 0.075c, respectively. The results show that MBLSS positively affects the power performance and aerodynamics of VAWTs. Parameter n has the most significant effect on VAWT power performance and the importance of d and l is determined by tip speed ratios (TSRs). Tight and loose slot arrangements are recommended for high and low TSRs, respectively. The relatively optimal configuration (n = 2, d = 0.025c, l = 0.05c) results in a remarkable 31.02% increase in the average net power output of the studied TSRs. The flow control mechanism of MBLSS for VAWT blade boundary layer flow has also been further complemented. MBLSS can prevent the bursting of laminar separation bubbles and avoid the formation of dynamic stall vortices. This increases the blade lift-to-drag ratio and mitigates aerodynamic load fluctuations. The wake profiles of VAWTs with MBLSS are also investigated. This study would add value to the application of active flow control techniques for VAWTs.

Aerodynamic characteristics of a square cylinder in streamwise sinusoidal flows

Aerodynamic characteristics of a square cylinder in streamwise sinusoidal flows

Mitigation of crosswind effects on high-speed trains using vortex generators

Vortex generators can enhance the operational safety of high-speed trains and offer effective anti-rolling performance. This paper investigates the influence of vortex generator installation angles on the aerodynamic characteristics of trains. The Improved Delayed Detached Eddy Simulation method is used to analyze the leeward side vortex structure. It is found that when the angle between the vortex generators and the relative wind is 30°, the rolling moment of the train is minimized, as it significantly reduces side forces while preventing excessive growth of lift force inducing rolling moment. The reduction in rolling moment of the train by vortex generators is attributed to the suppression of leeward side trailing vortices of the train, which delays flow separation at the roof of the train, inducing a downward trend in the separated flow. Dynamic Mode Decomposition reveals that vortex generators do not alter the stability of near-body trailing vortices but enhance the pulsatile characteristics of far-body trailing vortices, which do not affect the pressure distribution on the leeward side of the train.

Effect of trailing-edge blowing on the acoustic and aerodynamic characteristics of a flatback airfoil

This study investigated the impact of trailing-edge uniform air blowing on the acoustic and aerodynamic characteristics of a flatback airfoil. Near- and far-field pressure fluctuations, surface static pressure distribution, as well as boundary layer and wake flow measurements were conducted to comprehensively understand the effects of the method on both the noise generation mechanism and the aerodynamic characteristics of the airfoil. It was revealed that tonal noise originates from surface pressure fluctuations induced by upstream flow disturbances due to vortex shedding. The application of blowing was found to shift large-scale vortices generated during vortex shedding further downstream, resulting in the suppression of surface pressure fluctuations on both the pressure and suction sides of the airfoil, consequently reducing far-field noise. Additionally, blowing enhanced spanwise coherence at the vortex shedding frequency. In terms of aerodynamic behavior, blowing was shown to increase base pressure, leading to drag reduction without affecting lift. Interestingly, the significant drag reduction was found to occur at the same blowing parameter associated with maximum tonal noise reduction.

A machine learning-augmented aerodynamic database of rectangular cylinders

Rectangular cylinders submerged in a fluid encounter intricate aerodynamic forces, and the forces significantly influence the stability and safety of structures possessing a rectangular cross section. Although aerodynamic characteristics of these cylinders have been extensively studied, a comprehensive database cataloging these characteristics remains absent. This study conducted a large number of wind tunnel pressure testings to establish an aerodynamic database for rectangular cylinders with 2470 distinct configurations, including turbulent intensities ranging from 1% to 20%, side ratios ranging from 0.6 to 5, and wind attack angles ranging from 0° to 90°. The accuracy of the database was validated by data from the literature and wind tunnel force measurement experiments. More importantly, machine learning models were developed and have substantially expanded the experimental data, resulting in a comprehensive, continuous aerodynamic database for rectangular cylinders. By evaluating the model performance and verifying its generalization capability, the accuracy of the machine learning-augmented database is proved. This database is anticipated to serve as a critical reference for academic research and a practical reference for engineering applications.

Experimental and numerical studies of the processes of spraying coal-water slurries with pneumatic nozzle

The article presents the results of spraying tests of highly viscous coal-water slurries with a pneumatic nozzle and numerical studies of the structure of the gas-drop jet. An increase in the viscosity of coal-water slurries was ensured by introducing a third component into its composition – industrial waste (pyrogenetic liquid). The moderate effect of the slurry viscosity on the average droplet size of coal-water slurries in the jet is due to the high efficiency of the aerodynamic characteristics of the pneumatic nozzle. Introduction of pyrogenetic liquid in the amount of 20 % by weight into the composition of coal-water slurry significantly increases its viscosity. The value of the surface tension of such a slurry is more than doubled. The increase in the average droplet size was no more than 25 % when pyrogenetic liquid content in the composition of coal-water slurry was over 10 % by weight. The average droplet size of coal-water slurries varied in the range from 180 to 210 microns in the study area of gas droplet jet. The results of experimental and numerical studies have shown good convergence. High air velocities at short distances from the nozzle ensure high crushing efficiency of the jet of coal-water slurry. The breakdown of the boundary layer of the liquid from the periphery of the droplets of coal-water slurries and its subsequent destruction was observed at short distances from the nozzle. The values of the Weber number were 100<We<350. At considerable distances from the nozzle (more than 0.5 m), droplets of coal-water slurries were subjected to vibrational crushing (We<50).

Comparative Analysis of Turbulence Models for Evaluating the Aerodynamic Characteristics of Bus

Comparative Analysis of Turbulence Models for Evaluating the Aerodynamic Characteristics of Bus

Aerodynamic Characteristics of High-speed Train Pantographs Based on Jet Flow Control

Aerodynamic Characteristics of High-speed Train Pantographs Based on Jet Flow Control

Koopman neural operator approach to fast flow prediction of airfoil transonic buffet

Transonic buffet on airfoil is of great importance in the aerodynamic characteristics of aircraft. In the present work, a modified Koopman neural operator (KNO) is applied to predict flow fields during the transonic buffet process of the OAT15A [ONERA (National Office for Aerospace Studies and Research) Aerospatiale Transport aircraft 15 Airfoil] airfoil. Transonic buffet flow with different angles of attack is simulated by Reynolds averaged numerical simulation with the Menter's k−ω shear stress transport (SST) model at Reynolds number Re=3×106. A prediction model is directly constructed between the flow fields at several previous time nodes and that at the future time node by KNO. The predictions of flow fields with single sample and multi samples are performed to demonstrate the prediction accuracy and efficiency of KNO. The prediction of sequence flow fields based on the iterative prediction strategy is achieved for the transonic buffet process. The results indicate that KNO can achieve a fast and accurate prediction of flow physical quantities for the transonic buffet. Compared with other deep learning models including Unet and Fourier neural operator, KNO has a more advanced capability of predicting airfoil transonic buffet flow fields with higher accuracy and efficiency and less hardware requirements.

The Impact of Surface Structure Changes on the Aerodynamic Characteristics of Modern Soccer Balls

PURPOSE This study comprehensively examined the aerodynamic and flight characteristics of modern soccer balls, focusing on their design evolution and performance attributes. METHODS The aerodynamic characteristics of five types of World Cup balls (2006 Germany World Cup, 2010 South Africa World Cup, 2014 Brazil World Cup, 2018 Russia World Cup, 2022 Qatar World Cup) and five types of Euro tournament balls (EURO2008, EURO2012, EURO2016, EURO2020, EURO2024) were examined, along with their respective design changes. RESULTS Through detailed analysis, significant variations in aerodynamic properties among soccer balls used in various tournaments were identified. Recent advancements have resulted in faster transitions towards critical Reynolds numbers, indicating improved stability in flight trajectories. This enhancement was attributed to the augmentation of surface roughness, which plays a crucial role in enhancing aerodynamic stability and overall performance. 2D simulations simulating powerful goalkeeper kicks revealed distinct differences in flight distances among different soccer balls; the Jabulani ball used in the 2010 World Cup exhibited the longest flight distance, while that of the 2024 Euro ball was the shortest. CONCLUSIONS Variations in surface texture significantly impact aerodynamic properties, affecting flight distance, arrival time, and height. This study underscores the significant design enhancements in modern soccer balls that optimize aerodynamic stability and performance, with modifications aimed at improving flight characteristics and enriching player experience.

The Effect of Moveable Fins on Trajectory and Aerodynamic Characteristics of Model Rockets

The application of the fins on the rocket are necessaryto achieveoptimal flight performance. However, the appearanceof gust wind can affectthe stability of the rocket during flight. To minimize instability, the fins are designed to be adjustable by changing the fin cant angles.This study aims to investigate the effect of different cant angles on rocket’s trajectory and aerodynamic characteristicsthrough computer simulation.The Open Rocket software is used to conduct the simulations. The range of cant angle in this study is from0°to 15°and the Clipped Delta fin design is chosen for this study. The launch condition is all the same for all the model rocketsand the launch site’slatitude and longitude wasbased on Parit Raja location. The trajectory characteristics were evaluated through simulations of altitude versus position east of launch, altitude versus position north of launch, and altitude versus lateral distance. Meanwhile, the aerodynamic characteristics were evaluated through simulations of stability margin and drag force over time. This study found thatthe maximum altitude for each model rocket is decreasing as the cant angle increases. Different fin’scant angles slightly alter the trajectory characteristic of model rockets,but they do not significantly impact the overall stability and drag characteristics during critical phases of flight. Higher cant angles resulted in shorter horizontal and lateral distances from the launch site to the apogee, suggesting a more vertical trajectory.

Experimental and Numerical Determination of the Aerodynamic Characteristics of a Cruise Missile Model

A model of a cruise missile was tested in symmetrical air flow in a low-speed wind tunnel of the Military University of Technology (Warsaw, Poland). A virtual model of the missile was developed, and the geometry of the computational domain was built in the CAD environment of the ANSYS computational software suite. The domain was discretised in the ANSYS Meshing application, creating a hybrid computational mesh. Boundary conditions were determined in the ANSYS Fluent application, and physical (turbulent compressible flow) and numerical models were selected. Calculations were performed for three different turbulence models – Spalart-Almaras, realizable k-ε, and SST k-ω – and the results were compared to find the model providing the best convergence with in-tunnel measurements.

Assessing the possibility of using a variable-length launch vehicle with a polymer body for orbiting payload

The object of this study was the motion of an ultralight class variable-length launch vehicle made of a polymer body along the active phase of the trajectory. The work considers the solution to the problem of designing low-cost means of delivery to orbit, namely to the assessment of the possibility of removing the payload by a carrier rocket with a polymer body of variable length beyond the dense atmosphere of the Earth. For this purpose, ballistic projection of the trajectory of the launch vehicle was carried out taking into account overloading; its aerodynamic characteristics and peculiarities of aerothermodynamic processes occurring during flight in the atmospheric phase of the trajectory were determined. The closeness (up to 10 %) of the obtained results with known experimental data is shown. The influence of the aerodynamic force on the parameters of the launch vehicle motion was studied. A flight simulation was conducted, the results of which showed the fundamental possibility of launching a CubeSat 24U class payload using a launch vehicle with a polymer body of variable length to a suborbital trajectory with an altitude of about 300 km. At the same time, the effective longitudinal overload on the body of the launch vehicle does not exceed 4 units, and the temperature on the surface of the body does not exceed 300 K. A feature of the research is the use of a multidisciplinary approach, which implies taking into account the interrelationship of aerodynamic, thermodynamic, and ballistic processes. The established motion parameters, aerodynamic characteristics, and the surface heating temperature of the launch vehicle body are key values for further research on the design and analysis of a launch vehicle with a polymer body of variable length. These data could be used to calculate the mechanical and thermal loads acting on the structure of the launch vehicle during flight

Devising a technique for descending the illumination elements of aerial vehicles

The object of this study is the process of descending illumination elements equipped with a braking device in the form of two-bladed grills rotating in different directions. The classic parachute method does not provide the necessary speed of descent, it has low illumination parameters and significant drift of illumination elements by side wind. To solve the tasks set, mathematical dependences were obtained for calculating the aerodynamic characteristics of the descent device with the illumination element and its delivery to the ejection point. The drag and lift force coefficients during the flow around the blades of a dual-rotor impeller with different Reynolds numbers were determined by the method of numerical modeling based on the ANSYS CFX software package. The optimal geometric characteristics of the profile satisfying the condition for the necessary speed of descent of the illumination element at the given weight of the descent apparatus were determined. Reasonable requirements for illumination parameters and an improved composition of the flare have been proposed. A mathematical model of the movement of a body of variable mass to the point of ejection of the illumination element was built. The new design of the descent device makes it possible to reduce the speed of descent by 10–15 % and increase the weight of the payload by 20–30 %. The proposed illumination composition provides sufficient illumination of the object for 5 minutes with a light intensity of 2–2,5 million candelas and an average diameter of the illuminated area of 2000–2500 m. The mathematical model of the movement of a variable mass body to the point of the illumination element ejection makes it possible to determine with high accuracy the gun firing settings with illumination ammunition (30–40 % more accurate) and the time of ejection of illumination elements. Results of the current research make it possible to solve the scientific problem of ensuring the maximum efficiency of illuminating the terrain at night

Анализ воздействия воздушных обтекателей на аэродинамические характеристики токоприемника при увеличенных скоростях движения

Objective: investigation of the aerodynamic interaction of the airflow and the pantograph, taking into account the uneven distribution of pressure on the side edges of the fairings. Methods: the research was conducted based on a theoretical approach that defines the methods of air mass mechanics using mathematical modeling on a computer with the use of software products that include tools for calculating hydrodynamics based on the method of CFD analysis in the Flow Simulation module of the SolidWorks software. Results: a solid-state model of the current collector with integrated air deflectors has been developed, which takes into account the interaction complex in the system “moving structure — deflector — current collector — nodes and elements of the contact suspension” in the context of aerodynamic resistance influence. Practical importance: an innovative system has been developed to optimize the aerodynamic characteristics of the current collector during its motion in the air environment, an air deflector that contributes to reducing the negative impact of aerodynamic resistance, reducing the turbulence of air masses and improving the efficiency of current collection.