Aerodynamic Research Articles

Aerodynamic design optimization of locally built FSR Isuzu bus through numerical simulation

Reducing the fuel consumption of commercial vehicles—especially those used for public transportation—has become increasingly important due to advancements in the automotive industry. On the other hand, the main disadvantages of buses and other commercial vehicles are their fuel consumption, exhaust pollutants, and crosswind stability. Most buses built in Ethiopia have aerodynamic rectangular shapes and strong drag resistance forces, which lead to higher fuel consumption. One of the most accessible buses in Ethiopia is the FSR Isuzu Bus; its external body is locally constructed and has a poor aerodynamic shape. The primary goal of this study is to reduce aerodynamic drag force by improving the outer body shape of the current FSR Isuzu Bus. It also aims to examine the impact of roughness (strip) on the overall aerodynamic characteristics of the bus when it encounters crosswinds, thereby reducing fuel consumption, roll moment, and side force. For computational fluid dynamics (CFD) analysis, ANSYS Fluent is used, and Solidwork is used to model the bus body. A comparison is made between the current CFD analysis of the bus body and the modified design at varying speeds. Three separate models are used in the analysis. At an average speed of 100 kmph, 29.58% (4 to 5 liters) of fuel can be saved, and the drag force is reduced by roughly 49.7% when comparing the new concept to the current bus. By utilizing a strip on the bus’s roof, the side force coefficient and the roll moment coefficient are subsequently reduced from model two to model three by 8.76% and 9.01%, respectively. The study’s conclusions indicate that the external body shape changes have reduced drag; and, adding roof strips has decreased drag to acceptable level and enhanced crosswind stability.

Physics-inspired and data-driven two-stage deep learning approach for wind field reconstruction with experimental validation

Accurate and reliable wind forecasts for urban blocks play a pivotal role in the construction of zero-energy communities by guiding the selection and placement of wind turbines and the aerodynamic design optimization of ducted openings. While relatively accurate wind fields are available based on numerical methods, their heavy computational cost and discontinuity make it necessary to explore an interactive and end-to-end method. In this study, we develop a physics-inspired and data-driven two-stage deep learning approach that can reconstruct complex wind fields precisely. The proposed method integrates a physical feature extraction model of the flow field with a sparse measurement data-driven error correction approach. In particular, a well-designed and well-trained flow field feature extraction model (original model) can preserve salient features of CFD modelling, while data-driven error correction techniques may harvest the uncertainty features and fill the remaining gaps between the original model predictions and the measured data. The proposed method is verified by a measured dataset from a community in Beijing. Experimental validation illustrates that the proposed algorithm successfully accomplishes wind field reconstruction in complex terrains using sparse datasets. We show that the proposed two-stage strategy exhibits significantly improved prediction results over the purely original method, with an average accuracy improvement of 47.17% and a maximum accuracy improvement of 72.59%. Overall, the proposed method delivers the potential in accurate wind field construction and urban wind energy forecasting.

Investigation of tyre rim protectors on the aerodynamics of a passenger vehicle

The wheels of a passenger vehicle contribute to a significant part of the vehicle’s aerodynamic drag. The previous research has shown that the flow is sensitive to small geometrical variations of the tyre, such as its shoulder profile and tread pattern. This work investigates the effect of altering the tyre profile in the transition region between the tyre and the rim by adding a so-called rim protector. Full-scale wind tunnel tests capturing forces, flow fields and surface pressures were conducted for three tyre variants in combination with two rim configurations on a crossover SUV. With a low rim protector, the forces and flow fields were similar to the reference tyre without a rim protector for both rims. With a wide, protruding, rim protector on the open rim, a larger and more outwashed front wheel wake was obtained with differences in the vortex structures, resulting in a drag penalty of 0.017CD\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.017~C_D$$\\end{document}. The altered front wheel wake reduced the shielding of the rear wheel, resulting in differences in the rear wheel wake and base pressure. With a closed rim, the differences with the wide rim protector were much smaller with only a slight drag increase compared to the reference, demonstrating that there can be a strong interaction between the tyre and rim design.

Combining shape-adaptive blades and active flow control in a multi-stage axial compressor: a numerical study

AbstractShape adaption (SA) via piezo-ceramic actuation, and active flow control (AFC) by means of fluid injection and aspiration, are investigated within the Cluster of Excellence for Sustainable and Energy-Efficient Aviation (SE2A) with the goal of increasing the efficiency of multi-stage compressors—particularly at part-load, and of extending their operating range. Although both technologies have shown to be beneficial for the compressor off-design operation, drawbacks are still apparent at the aerodynamic design point when a single rotor or stator is equipped with SA or AFC, because of wake disturbances, which increase the incidence angle of the following row. Especially matching an improved component with its respective stage counterpart poses a major challenge in both research areas and is, therefore, addressed within this investigation. This work focuses on the first two stages of a high-pressure compressor, to compare and evaluate different combinations of shape adaption and active flow control. By considering structural requirements, such as a minimum blade thickness for the actuator application, and aerodynamic sensitivities, such as flow incidence and deviation due to off-design operation, a suitable configuration is derived and investigated in further detail.

Aerodynamic/control integrated optimization method for unpowered high-speed vehicle configuration design

The unpowered high-speed vehicle experiences a significant coupling between the disciplines of aerodynamics and control due to its characteristics of high flight speed and extensive maneuverability within large airspace. The conventional aircraft conceptual design process follows a sequential design approach, and there is an artificial separation between the disciplines of aerodynamics and control, neglecting the coupling effects arising from their interaction. As a result, this design process often requires extensive iterations over long periods when applied to high-speed vehicles, and may not be able to effectively achieve the desired design objectives. To enhance the overall performance and design efficiency of high-speed vehicles, this study integrates the concept of Active Control Technology (ACT) from modern aircraft into the philosophy of aerodynamic/control integrated optimization. Two integrated optimization strategies, with differences in coupling granularity, have been developed. Subsequently, these strategies are put into action on a biconical vehicle that operates at Mach 5. The results reveal that the comprehensive performance of the synthesis optimal model derived from the aerodynamic/control integrated optimization strategy is improved by 31.76% and 28.29% respectively compared to the base model under high-speed conditions, demonstrating the feasibility and effectiveness of the method and optimization strategies employed. Moreover, in comparison to the single-stage strategy, the multi-stage strategy takes into deeper consideration the impact of control capacity. As a result, the control performance of the synthesis optimal model derived from the multi-stage strategy improves by 13.99%, whereas the single-stage strategy only achieves a 5.79% improvement. This method enables a fruitful interaction between aerodynamic configuration design and control system design, leading to enhanced overall performance and design efficiency. Furthermore, it improves the controllability of high-speed vehicles, mitigating the risk of mission failure resulting from an ineffective control system.

Surrogate-based pneumatic and aerodynamic allocation design optimization for flapping-wing micro air vehicles

Determining the mapping relationships between the bionic structures and aerodynamic characteristics of flapping-wing micro air vehicles (FWMAVs), therefore optimizing their comprehensive performances of pneumatic functions and maneuvering capabilities, poses a formidable challenge. In this work, a surrogate-based approach is proposed to tackle the pivotal challenges. Firstly, an experimental surrogate model is established for predicting the pneumatic performances of the flapping wings using multi-fidelity datasets, which incorporates an efficient global optimization strategy for the sample fill-in to enhance predictive precision while minimizing experimental costs. Secondly, to account for the intricate influences of control inputs on aerodynamic characteristics, comprehensive aerodynamic surrogate models are established to precisely anticipate pneumatic performances and torque allocations under different attitude control patterns. Thirdly, by elucidating the mapping relationships between bionic structures and aerodynamic performances, surrogate-based optimizations aim to identify optimal combinations of corresponding parameters of bionic structures, thereby enhancing the pneumatic and toque allocations of the FWMAV. The bionic structures achieve a maximum lift enhancement of 11.5 % and at least a 5.4 % improvement in torque generation through experimental validations. Based on the optimal outcomes of the bionic structure analysis of the FWMAV, a novel prototype family comprising three distinct sub-varieties is successfully fabricated. The findings of our research are hopefully to offer valuable insights for future FWMAV designs and make potential contributions to the advancement of standardized methodologies for evaluating their flight performances.

Low-Speed Space Launch System Computational Fluid Dynamics: A Comprehensive Overview

In this review paper, low-speed computational work from NASA Langley Research Center in support of the Space Launch System (SLS) is discussed. This information includes both historical and present efforts with the Kestrel computational fluid dynamics solver. The low-speed aerodynamics of SLS is highly complex, and the analysis of the unsteady flowfield requires significant computational efforts. The SLS mission profile varies from the vehicle static on the launch pad through high-speed ascent. This study focuses on the prelaunch as well as liftoff and transition portions of the flight both in proximity to the launch tower and in isolation. High-alpha conditions, as large as 90 deg, result in a flowfield dominated by massive, large-scale flow separation and asymmetric vortices. High-fidelity solutions require an unsteady computational formulation to accurately capture the aerodynamics of the vehicle. A detailed discussion of the computational approach is presented, followed by key efforts to support the program, both historic and present, including information that has been either published previously or that has never before been published external to NASA.

Aerodynamic design and validation strategy on hole-shaped pre-swirl nozzles

Aerodynamic design and validation strategy on hole-shaped pre-swirl nozzles

Experimental and numerical investigation of the aerodynamic characteristics of high-performance vehicle configurations under yaw conditions

This study investigates the impact of yaw conditions on the aerodynamic performance and flow field of three high-performance vehicle model configurations by means of wind tunnel testing and unsteady Reynolds-Averaged Navier–Stokes-based computational fluid dynamics simulations. While yaw effects on automotive vehicles have been explored, the effects on far more complex flow fields of high-performance vehicles remain insufficiently researched. This paper reveals that yaw conditions have a significant negative influence both downforce and drag performance. Spoiler and rear wing devices enhance downforce but increase the vehicle's sensitivity to yaw. Furthermore, yaw conditions significantly alter vortex structures and local flow velocities, affecting downstream flow behavior. Surface pressure measurements on the slant confirm these findings and highlight notable yaw effects and upstream effects from spoiler and rear wing devices. Wake analyses through total pressure measurements show that yaw induces a substantial deviation from straight-line wake characteristics, which become dominated by an inboard rotating vehicle body vortex. Overall, this research enhances the understanding of the effects of yaw conditions on high-performance vehicle aerodynamics and provides valuable data for future vehicle aerodynamics research in real-world operating conditions.

Wind-structure interaction mechanism of circular storage shells- a critical review

A critical review on the valuable researches about the aerodynamic load and consequent structural behavior of cylindrical storage shells, has been carried out. The wind-shell interaction mechanism has been explored through literatures to understand aerodynamic pressure characteristics, wind-induced vibration, buckling and design of cylindrical storage shell and stiffener. Important input parameters have been presented in a tabulated manner so as to correlate and compare critical output parameters (graphically) with an emphasis on circumferential wind pressure coefficient and radial deflection per unit thickness under wind-induced buckling. The scopes for future studies in this field of research have also been recommended.

Ground effect of an inverted double element wing diffuser on a sedan car

The diffuser is a critical component in sports cars, enhancing aerodynamics by increasing downforce and reducing drag. Previous studies have focused on its dependence on diffuser incidence, height, and base pressure. The design of the car, particularly the rear end shape and the rear wing's presence, affect base pressure and the diffuser's performance. Previous studies have investigated the effects of diffuser geometry on aerodynamic performance, but the current study is the first to examine the relationship between the diffuser and the rear tires. It also provides specific and quantitative results on the impact of different diffuser design parameters on drag and downforce. The relationship between the rear tires and the double-element inverted wing diffuser using computational fluid dynamics (CFD) was investigated. This is an essential problem because the diffuser is a critical component of sports cars, and its design can significantly impact aerodynamic performance. CFD was used to simulate the flow of air around the car model. The CFD model was based on the Nissan Sunny (Versa) type Almera design, and the diffuser main element and flap wing angles were set at 4 and 15.5°, respectively. The flap gap, overlap distance, and wing ride height above the ground were varied to achieve an optimal aerodynamic design. The study found that the wing's ride height significantly influences the flow through the diffuser. The diffuser significantly impacts base pressure and downforce production. Increasing the ride height decreases base pressure, leading to an increase in downforce until a specific point near the car body, where downforce further increases. The study concluded that the best double-element diffuser design was selected based on lift-to-drag results and the allowable dimensions of the car, wing ride height, element gap, and overlap distances. Ultimately, the best diffuser wing design features a ride height of 154 mm, a gap distance of 10 mm, and an overlap of 5 mm. This design reduces drag by approximately 2.7 % and remarkably increases downforce ten times compared to the baseline car model.

Effects of cornering conditions on the aerodynamic characteristics of a high-performance vehicle and its rear wing

This study investigates the aerodynamic behavior of a high-performance vehicle and the interaction with its rear wing in straight-line and steady-state cornering conditions. Analyses are performed with Reynolds-averaged Navier–Stokes based computational fluid dynamics simulations using a moving reference frame and overset mesh technique, validated against moving ground wind tunnel experiments. The results indicate a significant 20% decrease in downforce and 35% increase in drag compared to straight-line conditions at the smallest considered corner radius of 2.9 car-lengths. Downforce losses primarily stem from performance deficits on the underbody and rear wing, alongside elevated upper body lift. Drag penalties mainly result from additional pressure drag induced by a recirculation wake vortex generated behind the vehicle's inboard side. The vehicle's lateral pressure distribution is also affected, introducing a centripetal force that increases with smaller corner radii. Additionally, analyses of the rear wing reveal alternations of its aerodynamic characteristics in cornering, particularly impacting vortical flow and suction on the lower surface. Throughout the operating conditions, the rear wing's individual downforce contribution falls off beyond its stall angle. At higher angles of attack, the rear wing primarily generates downforce by pressurizing the vehicle's upper surfaces, but its interaction with the near-wake leads to a substantially increased pressure drag. Overall, these findings provide crucial insights into the intricate aerodynamic interactions of high-performance vehicles in diverse operating conditions as well as form an essential foundation for future research on static and active aerodynamic designs in the pursuit to optimize vehicle performance in dynamic driving conditions.

Optimization of a high through-flow design turbine using response surface method

Enhancing the through-flow capability of the turbine facilitates the potential to decrease the external dimension of the engine, leading to a reduction in weight and an increase in the thrust-to-weight ratio. The optimization of blade profile in terms of aerodynamic design is an essential strategy to improve the overall performance of the high through-flow design turbine. This study aims to develop an automated optimization technique, utilizing the response surface method (RSM), to enable reliable prediction and rapid optimization of aerodynamic performance. A parametric modeling method is devised to generate blade profiles with continuous curvature throughout the automated optimization process. The Box–Behnken experimental design, in combination with Reynolds-averaged Navier–Stokes numerical calculation, is employed to construct a second-order polynomial RSM approximation model. The optimization process comprises two levels: improving the through-flow capability and reducing blade profile loss. The optimized profile, Opt1, achieves a substantial 13.19% improvement in through-flow capability at the cost of a 12.27% increase in blade profile loss. Thus, further optimization is performed to minimize blade profile loss based on the Opt1 scheme. Geometric constraints are applied to the most influential parameters affecting through-flow capability to mitigate their impacts. Compared to the Opt1, the final optimized profile, Opt2, achieves a substantial 31.83% decrease in blade profile loss with a negligible sacrifice of 0.23% in through-flow capability.

Aerodynamic Design and Performance Analysis of Mars Ascent Vehicles

The mid-lift-to-drag ratio vehicle possesses larger dimensions and enhanced aerodynamic characteristics compared to the conventional sphere-cone reentry vehicle, suggesting its suitability for crewed missions to Mars. This research employs Computational Fluid Dynamics (CFD) simulations to investigate the influence of varying geometries on the aerodynamic properties of mid-lift-to-drag ratio vehicles. The aerodynamic analysis of four distinct configurations demonstrates that a bow shock wave forms on the windward side, leading to a reduction in flow velocity and subsequent increases in pressure and temperature after the shock wave. The simulation results for the four configurations in both laminar and turbulent flow conditions, specifically using the Shear-Stress Transport (SST) model, reveal that turbulence results in higher aerodynamic heating compared to laminar flow. Moreover, the aerodynamic heating is greater at a 40° angle of attack than at 30°. In this study, the transition phenomena of four geometric configurations are examined using the k-ω-γ transition model. The findings indicate a pronounced transition to turbulence on the windward side of the Ellipsled 2.00-0.25 and Hammerhead-Nominal configurations under conditions of high Reynolds numbers, transitioning from laminar to turbulent flow. The investigation into the aerodynamic characteristics of mid-lift-to-drag ratio vehicles holds substantial importance for ensuring the safety and success of Martian reentry missions, highlighting the critical nature of aerodynamic behavior in the context of space exploration.

Design and analysis of a bionic‐inspired single‐rotor MAV with a foldable wing

AbstractMicroaerial vehicles (MAVs) have achieved rapid advancement and vast applications. Energy efficiency and friction loss are common problems of MAVs, and exploring novel structural design and enhancing flight performance are critical research directions. Here, a bionic‐inspired single‐rotor MAV with a foldable wing is fabricated by imitating winged achene in nature. The structural design of the wing based on origami principle, overall aerodynamic modeling analysis, kinematic analysis, and control system design is carried out. The prototype weighs 75 g and equipped with only one motor, achieved the desired flight attitude of vertical takeoff and landing, hovering and horizontal flight, and so forth. During nonflight, the wings fold down can reduce 70% storage area for easier transportation. The vehicle combines high flight efficiency with compactness, superior stability, simple structure, economical manufacturing cost, low flight noise, and spin deceleration safety protection, which has good potential for application in the aerial vehicle fields.

Toward the Usage of Deep Learning Surrogate Models in Ground Vehicle Aerodynamics

This study introduces a deep learning surrogate model designed to predict the evolution of the mean pressure coefficient on the back face of a Windsor body across a range of yaw angles from 2.5∘ to 10∘. Utilizing a variational autoencoder (VAE), the model effectively compresses snapshots of back pressure taken at yaw angles of 2.5∘, 5∘, and 10∘ into two latent vectors. These snapshots are derived from wall-modeled large eddy simulations (WMLESs) conducted at a Reynolds number of ReL=2.9×106. The frequencies that dominate the latent vectors correspond closely with those observed in both the drag’s temporal evolution and the dynamic mode decomposition. The projection of the mean pressure coefficient to the latent space yields an increasing linear evolution of the two latent variables with the yaw angle. The mean pressure coefficient distribution at a yaw angle of 7.5∘ is predicted with a mean error of e¯=3.13% when compared to the WMLESs results after obtaining the values of the latent space with linear interpolation.

A rapid method for turbomachinery aerodynamic design and optimization using active subspace

Preliminary design is a crucial step in the turbomachinery aerodynamic design process, which involves the initial conceptualization and serves as the foundation for subsequent detailed design and analysis. During preliminary design, designers typically use a combination of empirical correlations, simplified flow models, and computational tools to evaluate the impact of different design parameters on the machine’s performance. This iterative process heavily relies on the designer’s experience and knowledge, and errors made during preliminary design may not be rectifiable in later design phases. To address this challenge, this paper proposes a novel optimization strategy for turbomachinery aerodynamic preliminary design using active subspace. The method utilizes active subspace techniques to reduce the dimensionality of the design space, making efficient and accurate exploration of the space possible. In addition, the open-access <italic>Multall</italic> turbomachinery design suite is employed to evaluate the aero-thermal performance of different designs. The method was then utilized to optimize the aerodynamic design of the blade profile for a ducted fan. Results show that the optimization strategy can identify the most significant directions in the design space, providing designers with a clear path to achieving an optimal design. Overall, the proposed method can be of good value to the turbomachinery design community attribute to its reduced dependence on the designer’s experience and elevated efficiency of the design process.

The detrimental effect of thermal exposure and thermophoresis on MHD flow with combined mass and heat transmission employing permeability

We look at the viscous free-convective transitional magnetohydrodynamic thermal and mass flow over a plate that is always perforated and standing upright through permeable media while thermal radiation, a thermal source, and a chemical reaction are all going on. There is additional consideration for the Soret effect. The plate receives a normal application of a transversely consistent magnetic field. The magnetic Reynolds number is considerably lower considering the axial applied magnetic field instead of the induced magnetic field. The models that control mass, heat, and fluid flow are turned into two-dimensional shapes, and the answers are found by running numerical simulations using the MATLAB algorithm bvp4c. In realistic circumstances, the outcomes have been illustrated graphically. Several fluid properties have been found to have an impact on velocity, temperature, and concentration profiles. There is noticeable increase in velocity along with the growth of the permeability parameter and Soret number. Other dimensionless parameters have a significant impact on the fluid velocity. Likewise, the temperature profile diminishes as the radiation parameter has increased. The concentration distribution falls as the heat source parameter expands. Also, the analysis is encompassed in tabular form for the shearing stress, Nusselt number, and Sherwood number. The combined knowledge of heat and mass moving through viscous flows can be used to make a wide range of mechanisms and processes. These include biological reactors, therapeutic delivery systems, methods of splitting, aerodynamic aircraft design, and modeling for sustainability. It also optimizes automotive radiators and engine efficiency, and it improves cooling systems.

Aerodynamic performance of a flyable flapping wing rotor with dragonfly-like flexible wings

Drawing inspiration from insect flapping wings, a Flapping Wing Rotor (FWR) has been developed for Micro Aerial Vehicle (MAV) applications. The FWR features unique active flapping and passive rotary kinematics of motion to achieve a high lift coefficient and flight efficiency. This study thoroughly investigates the aerodynamic performance and design of a bio-inspired flexible wing for FWR-MAVs, emphasizing its novel backward-curved wingtip and variable spanwise stiffness resembling a dragonfly's wing. The research departs from previous aerodynamic studies of FWR, which focused predominantly on rectangular and rigid wings, and delves into wing flexibility. Employing Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and experimental measurements, the study demonstrates the aerodynamic benefits of the dragonfly-inspired FWR wingtip shape and its reinforced structure. Fluid-Structure Interaction (FSI) analysis is used to examine the effects of elastic deformation encompassing twist and bending on aerodynamic forces. The results underscore the importance of bending deformation in enhancing lift and power efficiency and propose a method for analysing variable stiffness along the wingspan using a vortex delay mechanism that is induced by delayed flapping motion. By comparing modelled and measured stiffness, the study validates the flexibility of the FWR wing, revealing optimal aerodynamic efficiency is achieved through moderate flexibility and spanwise stiffness variation. The curving leading-edge beam forming the sweep-back wingtip offers a practical approach to obtaining variable stiffness and aerodynamic benefits for FWR-MAVs. Using the same pair of dragonfly-like flexible wings, FWR-MAVs have effectively exhibited VTOL and hovering flight capabilities, spanning from a 25-g single-motor drive model to a 51-g dual-motor drive model. This research provides valuable insights into flexible wing design for FWR-MAVs, leveraging biomimicry to improve flight efficiency.

Flow physics during durge of an axial-centrifugal compressor

Aerodynamic instability design is one of the crucial elements when designing a compressor. Unstable phenomenon such as surge harms the compressor in both performance and structure integrity. The complex unsteady flow process during instability strongly relates to the compressor design. This paper investigates the transient instability process using URANS on a three-stage-axial and one-stage-centrifugal combined compressor under its off-design conditions. Results show that the compressor suffers two surge patterns. The mild surge happens first, with a higher frequency than the traditional mild surge. Then, with the decrease of valve opening, the deep surge is initiated, and the axial stages work at the peak pressure ratio because the mass flow rate is limited by the choked radial diffuser. Moreover, analysis of aerodynamic loads reveals that IGV and the first rotor have the largest unsteady force among all blade rows. According to the flow field, the rotor root and stator tip suffer the most serious impulse caused by reversed flow during surge conditions.