Aerodynamic Study Research Articles

Research and Analysis of the Small Disturbance Equation in Subsonic, Transonic, and Supersonic Regimes

This paper explores the application of the Small Disturbance Equation (SDE) across subsonic, transonic, and supersonic flow regimes. Derived from the Euler and Navier-Stokes equations, the SDE offers an efficient framework for analyzing aerodynamic behaviors, particularly through the utilization of discretization techniques and iterative solving methods executed in Python. The study assesses the accuracy and limitations of the SDE in detailing essential flow characteristics, revealing that while the equation performs effectively in subsonic and transonic flows, it encounters challenges in supersonic regimes. Nonlinear effects such as shock waves significantly hinder its performance at high speeds. Compared with conventional computational fluid dynamics (CFD) methods, the SDE stands out in scenarios where computational efficiency is paramount. However, its limitations in handling high-speed flows must be carefully considered, highlighting the need for further refinement in its application to supersonic dynamics. This analysis suggests that while the SDE is beneficial for certain aerodynamic studies, its scope and utility are constrained by the inherent complexities of high-speed fluid dynamics.

Aerodynamic study of a leading-edge rotating cylinder in a cambered aerofoil (NACA2412)

Purpose Flow separation over an aircraft’s wing beyond a specific angle of attack is challenging. Flow boundary layer manipulation has been investigated to improve aerofoil lift and mitigate flow separation difficulties including stall and drag. This is solved via active or passive flow control. Active flow control method moving surface boundary (MSB) enhances shear flow momentum, making it effective. MSB is easier than suction and blowing. Asymmetrical airfoils, which generate lift in aircraft wings, have received less MSB research than symmetrical ones. The purpose of this study is to asses the design efficacy of MSB’s NACA 2412 aerofoil. Design/methodology/approach To observe the performance of MSB in NACA 2412, a computational model has been created, and aerodynamical performance has been analyzed. Findings The study results show that the NACA 2412 with MSB has better aerodynamic efficiency than the NACA 2412 base design. It works best when it reaches its optimal speed and the delay in flow separation works well. Research limitations/implications Limitations may include specific aerofoil applicability, external factors and simulation constraints. Implications guide future research for broader insights and applications. Practical implications Improving asymmetrical aerofoil performance, mitigating stall effects, reducing drag and optimizing designs with moving surface boundary. Insights gained can enhance overall aircraft efficiency and flow control techniques. Originality/value The MSB flow control in a chambered aerofoil is less explored and not explored enough in wing-based aerofoils, and the optimal cylinder speed ratio trend has been discussed at each angle of attack studied.

A numerical analysis of isolated propeller noise using a lattice Boltzmann method approach

Current environmental needs to achieve carbon neutral commercial aviation by 2050 require the development of new technologies and aircraft configurations. Among the different technological developments proposed, the use of open fan or Ultra-High Bypass Ratio configurations is of interest due to their higher propulsive efficiency and performance. To support the development of such technologies, accurate and efficient tools early in the design stages are needed to predict aerodynamic performances and noise levels. One such tool is the lattice Boltzmann method, which can perform high-fidelity aeroacoustic simulations of flows around propellers and engines. The lattice Boltzmann approach can be advantageous over other numerical methods due to its easy integration with complex geometries, its low numerical dissipation properties, and its high level of computational efficiency. This paper presents the aerodynamic and aeroacoustic numerical study of an isolated propeller using the commercial lattice Boltzmann solver ProLB. Large Eddy Simulations were carried out using a compressible hybrid thermal version of the solver. An aeroacoustic analysis using a Ffowcs-Williams and Hawkings acoustic analogy for far-field noise was carried out. The objective is to assess the capabilities of the solver to predict acoustic emissions of an isolated propeller towards the future study of an installed case.

Design and aerodynamic performance study of subsonic Y-shaped inlet

Abstract A Y-shaped inlet with a quadrate import was designed by the super-ellipse method in this paper, and according to the variation pattern of the cross-section of the inlet, the variation pattern of the short and long axis of the super-ellipse was deduced. For many different flight situations, the numerical simulations of the Y-shaped inlet were made. The result shows (1) If 0.2≤Ma≤0.8, the total pressure recovery coefficient exceeds 0.96, and the total pressure distortion coefficient is close to 0.1, meeting the criterion of the design; (2) When Ma=0.8, for many different attack angle α=-4°∼22°, the total pressure recovery coefficient is close to 0.97, reaching the level of practical application, and it has little impact on total pressure recovery coefficient and the distortion coefficient. (3) These results demonstrate high total pressure recovery and low distortion coefficients across various flight conditions, indicating its potential for practical applications and future inlet designs.

Aerodynamic Simulation Study of a Space Vehicle with Atmosphere-Breathing Electric Propulsion in a Free Molecular Gas Flow

Aerodynamic Simulation Study of a Space Vehicle with Atmosphere-Breathing Electric Propulsion in a Free Molecular Gas Flow

Aerodynamic Study of Successful Mars Entry Vehicles

Aerodynamic Study of Successful Mars Entry Vehicles

Aerodynamic Study of a Horizontal Axis Wind Turbine in Surge Motion Under Angular Speed and Blade Pitch Controls

Aerodynamic Study of a Horizontal Axis Wind Turbine in Surge Motion Under Angular Speed and Blade Pitch Controls

Effects of endplate designs on the performance of Savonius vertical axis wind turbine

In aerodynamic studies, endplates or wingtip devices play a crucial role in enhancing the performance of airfoil blades and minimizing losses. This is particularly important for wind turbines, especially the drag-type Savonius turbine. This paper aims to investigate the effects of different endplate designs. Both experimental works and numerical simulations were conducted on a Savonius rotor with an aspect ratio of 1. A total of eight different endplate geometries and sizes were investigated. The mechanical torque and rotational speed were measured experimentally under various loads with an incoming wind speed of 5.89 m/s. The coefficient of torque (CT) and coefficient of power (CP) were calculated in both the experiments and simulations. The simulation was first validated using data from the literature, and flow characteristics were then scrutinized. The results indicate that the endplates greatly impact the turbine performance, with improvements of up to 299.7 % compared to a turbine without endplates from the experiment. The endplates help prevent flow leakage near the blade edges. In addition to tip losses reducing turbine performance, aerodynamic parasitic drag also contributed to a decrease in CP for the full endplate. The relationship between the aerodynamic parasitic drag with TSR is also reported. By implementing a well-designed endplate, these adverse effects can be mitigated.

Design and characterization of the university of Toronto hybrid anechoic wind tunnel

A detailed overview of the hybrid anechoic wind tunnel at UTIAS is presented, highlighting its design and performance features. The findings demonstrated that the tunnel achieves a uniform flow with very low turbulence intensity, matching the performance of similar open-loop wind tunnel facilities. The anechoic chamber effectively reduces noise with a cutoff frequency of around 160 Hz, providing a suitable environment for a broad spectrum of aeroacoustic measurements. The versatility of the wind tunnel was illustrated through its application in various aerodynamic and aeroacoustic studies, showcasing examples such as the NACA 0012 airfoil, the multi-element 30P30N configuration, and finite-span airfoil investigations. Moreover, the facility's Overall Sound Pressure Level (OASPL) is on par with other prominent global aeroacoustic wind tunnels, indicating its competitive performance and utility in the field.

Aerodynamic Study of Different Types of Wingtip Devices

Aerodynamic Study of Different Types of Wingtip Devices

Design and aerodynamic stability improvement study of a non-axisymmetric stator fan in a distorted insertion plate configuration

The design of anti-distortion fans must ensure the reliable operation and flight safety of propulsion systems under inlet distortion conditions. This research uses an insertion plate to obtain the inlet distortion flow field for a specific type of turbofan engine. Based on the characteristics of distortion effects, a novel strategy is proposed to rapidly implement a non-axisymmetric stator (NAS) quasi-three-dimensional design to create anti-distortion fan designs and improve the performance and stability of the fan in distortion environments. Numerical studies show that under three rotational speed operating conditions, the NAS effectively improves the total pressure ratio and efficiency characteristics of the fan under inlet distortion conditions. Compared to the prototype, the NAS can significantly increase the stability margins by 10.31 %, 8.31 %, and 7.39 % under the three different speed operating conditions, which effectively expands the stability boundaries. The NAS design directly affects the distortion region, effectively improves the incidence angle of stator vanes in the distortion region, suppresses the development and migration of vortices inside the stator passage, and significantly reduces the stator vane diffusion factor. Because it effectively eliminates corner separations and makes the incidence angle distribution of stator vanes relatively circumferentially uniform, the internal flow field of the fan's stator vanes and overall aerodynamic performance of the fan improve. Furthermore, the NAS design can improve the internal flow field downstream of the fan, direct the nonuniform flow field at the inner bypass outlet toward circumferential uniformity, and effectively improve flow field uniformity.

A multi-directional redundant 3D-LPT system for ship–flight–deck wind interactions

In the past years, volumetric velocimetry measurements with helium-filled soap bubbles as tracer particles have been introduced in wind tunnel experiments and performed at large-scale, enabling the study of complex body aerodynamics. A limiting factor is identified in the field of wind engineering, where the flow around ships is frequently investigated. Considering multiple wind directions, the optical access for illumination and 3D imaging rapidly erodes the measurement regions due to shadows and incomplete triangulation. This work formalizes the concepts of volumetric losses and camera redundancy, and examines the performance of multi-directional illumination and imaging for monolithic and partitioned modes. The work is corroborated by experiments around a representative ship model. The study shows that a redundant system of cameras yields the largest measurement volume when partitioned into subsystems. The 3D measurements employing two illumination directions and seven cameras, yield the time-averaged velocity field around the ship. Regions of flow separation and recirculation are revealed, as well as sets of counter-rotating vortices in several stations from the ship bow to the flight–deck. The unsteady regime at the flight–deck is examined by proper orthogonal decomposition, indicating that the technique is suited for the analysis of large-scale unsteady flow features.

Aerodynamic study of high-speed railway tunnels with variable cross section utilizing equivalent excavation volume

High-speed railway tunnels, being critical components of transportation infrastructure, are subject to various aerodynamic effects that can impact train operations and passenger comfort. To address these challenges, the concept of tunnels with variable cross sections offers a promising solution, allowing for non-uniform adjustments to tunnel geometry along its length. By employing the notion of equivalent excavation volume, this paper aims to provide a comprehensive aerodynamic analysis of variable cross section tunnels, focusing on different rates of cross section variation (CR). The simulation of high-speed trains (HSTs) passing through tunnels is conducted using the compressible, unsteady Reynolds-Averaged Navier–Stokes model, and the accuracy is confirmed through experimental validation. The transient pressure and peak distribution, slipstream characteristics, micro-pressure waves, and aerodynamic loads acting on trains are fully evaluated. The results indicate that variable cross section tunnels can alleviate the negative pressure on train surface, particularly with streamlined heads and tails exhibiting superior effects, whereas its influence on positive pressure is minimal. The mitigation of both positive and negative pressures on the tunnels is promising, with the maximum peak-to-peak pressures exhibiting a quadratic decrease as the CR increases, resulting in a maximum relief of 17.7%. However, variable cross section tunnels have certain adverse effects on slipstreams and transient loads when HSTs passing through front junctions. Therefore, it is necessary to choose an appropriate CR to control these effects during design process. The findings of this research contribute novel insight for optimizing tunnel design and engineering practices to enhance operational efficiency and passenger comfort.

Eulerian–Lagrangian hybrid solvers in external aerodynamics: Modeling and analysis of airfoil stall

Hybrid computational solvers that integrate Eulerian and Lagrangian methods are emerging as powerful tools in computational fluid dynamics, particularly for external aerodynamics. These solvers rely on the strengths of both approaches: Eulerian methods efficiently handle boundary layers, while Lagrangian methods excel in reducing numerical diffusion in flow convection. Building on our prior development of a two-dimensional hybrid solver that combines OpenFOAM with vortex particle method, this paper extends its application to the complex phenomena of airfoil stall at low Reynolds numbers. Specifically, we examine both static and dynamic stall conditions of a National Advisory Committee for Aeronautics (NACA) airfoil series 0012 (NACA0012) across a wide range of attack angles and oscillation frequencies, comparing our results with established data. The findings demonstrate the accuracy of hybrid Eulerian–Lagrangian solvers in replicating known stall behaviors, underscoring their potential for advanced aerodynamic studies. This work not only confirms the capability of hybrid solvers in accurately modeling challenging flows but also paves the way for their increased involvement in the field of external aerodynamics.

The Impact of Using Dimpled Surfaces on Ahmed Body on The Flow Characteristics

Vehicle aerodynamics which directly affects fuel consumption values in vehicles has great importance in terms of vehicle stability, acceleration ability, vehicle noise, and environmental pollution. Ahmed car model is one of the most important generic models, so this popular car model is widely used in the literature on fluid mechanics and vehicle aerodynamics studies. This study investigates the effect of a passive drag reduction technique which is known as dimple surface, on Ahmed car model with a 35° slant angle. The flow control methods were applied numerically also these methods were compared with similar works. Analysis made in this study were conducted with 2.4 million cell numbers and the maximum drag reduction is 3.5 % with optimum dimple surfaces. Moreover, the applicability and manufacturability factors were also evaluated in terms of implementing the dimpling modification to today’s current road vehicles.

Aerodynamic Study of Velopharyngeal Insufficiency in 22q11.2 Deletion Syndrome.

We aim to verify velopharyngeal sphincter function in 22q11.2 deletion syndrome patients (22q11.2DS) to establish correlations between aerodynamic and perceptual measures of nasality, and to identify aerodynamic measures differentiating typical from atypical velopharyngeal behavior. Eleven subjects with 22q11.2DS and twenty similar-age control subjects were recruited. The aerodynamic measures were mean Sound Pressure Level, air pressure peak, pressure wave duration, airflow pattern and nasal airflow during the sequence /pi/. The nasality perceptual measures were rhinolalia, rhinophony and nasal air escape. Airflow patterns and perceptual measures were statistically different in the two groups. Pressure wave duration and air pressure peak were lower in study subjects than in controls. Air pressure peak and nasal airflow were negatively correlated with rhinolalia; pressure wave duration was negatively correlated with nasal air escape and rhinolalia in 22q11.2DS patients. This aerodynamic study identified velopharyngeal qualitative and quantitative dysfunctions, suggesting heterogeneous models of velopharyngeal function in syndromic subjects as compared to controls.

On the Size of the Step Along the Azimuth of the Wind Flow During Aerodynamic Studies of High-Rise Buildings

On the Size of the Step Along the Azimuth of the Wind Flow During Aerodynamic Studies of High-Rise Buildings

Aerodynamic design optimization of a NACA 0012 airfoil: An introductory adjoint discrete tool for educational purposes

The adjoint method is a powerful tool in high-fidelity aerodynamic shape optimization, providing an efficient means to compute derivatives of a target function with respect to various design variables. This paper delves into the discrete adjoint method. It offers a theoretical exploration of its implementation as an innovative tool for calculating partial derivatives (sensitivities) related to objective functions and design variables, specifically applied to a subsonic NACA0012 airfoil. The study conducts a qualitative evaluation using a designated test case, considering specified Mach number and Reynolds number values of 0.297 and 6,667 million, respectively. The Spalart-Allmaras turbulence model is employed to enhance computational cost efficiency. The results affirm the efficacy of the introduced tool, DAFoam, showcasing its ability to generate optimal geometries. The achieved performance optimization is evidenced by minimizing the drag coefficient value (CD) to an impressive 0.0131. While this research does not delve into the post-processing of sensitivity calculations, it acknowledges the potential for future investigations. The primary objective and novelty of this study is to provide the elementary background of the state of the art test case (NACA0012) within the subsonic regime, introducing the pioneer discrete adjoint aerodynamic optimization methodology (DAFoam) with the potential to explore its higher order capabilities in other aerodynamic related studies. Furthermore, it caters the educational needs of both graduate students and engineers in this exciting field. By presenting this cutting-edge methodology, it contributes to future advancements for the aerodynamicists in terms of optimal solutions.

Relative Fundamental Frequency: Only for Hyperfunctional Voices? A Pilot Study.

(1) Background: Assessing phonatory disorders due to laryngeal biomechanical alterations requires aerodynamic analysis, assessing subglottic pressure, transglottic flow, and laryngeal resistance. This study explores whether the acoustic parameter, the relative fundamental frequency (RFF), can be studied using the current acoustic analysis protocol at the University of Navarra's voice laboratory and its association with pathologies linked to laryngeal biomechanical alterations. (2) Methods: A retrospective cohort study included patients diagnosed with muscular tension dysphonia, organic lesions of the vocal fold, and vocal fold paralysis (VFP) at the Clínica Universidad de Navarra from 2019 to 2021. Each patient underwent endoscopic laryngeal exploration, followed by acoustic study, RFF calculation, and an aerodynamic study. Additionally, a control group was recruited. (3) Results: 79 patients and 22 controls were studied. Two-way ANOVA showed significant effects for groups and cycles in offset and onset cycles. Statistically significant differences were observed in cycle 1 onset among all groups and in cycles 1 and 2 between the control group and non-healthy groups. (4) Conclusions: RFF is a valuable indicator of phonatory biomechanics, distinguishing healthy and pathological voices and different disorders. RFF in onset cycles offers a cost-effective, accurate method for assessing biomechanical disorders without complex aerodynamic analyses. This study describes RFF values in VFP for the first time, revealing differences regardless of aerodynamic patterns.

Enhancing accuracy of surface wind sensors in wind tunnel Testing: A Physics-Guided neural network calibration approach

Irwin’s surface wind sensor is widely used in wind tunnel testing for urban and environmental aerodynamics studies. However, the conventional physics-based calibration of this sensor could result in reduced measurement accuracy in regions with low flow velocities and high turbulence intensity. To address this issue, this study proposes a novel physics-guided neural network (PGNN) calibration approach, which couples a physics-based calibration model, derived from extended Taylor series expansions of measured wind speed, with an adaptive, data-driven general regression neural network. Sensors are calibrated within the turbulent boundary layer of an empty flat plate, considering both mean and standard deviation of wind velocity measured by high-accuracy thermal anemometry. The accuracy of calibrated sensors is then assessed using a 1:400 benchmark urban model. Experimental results show significant improvement in measurement accuracy, reducing mean absolute percentage error for wind speed standard deviation from 92.3 % with the current model to 9.8 % using PGNN.