Aerodynamic Testing Research Articles

Numerical prediction of aerodynamic noise from impeller blowers of straw threshing machines

An impeller blower is one of the major aerodynamic noise sources in straw threshing machines. To reduce its aerodynamic noise, it is essential to understand the mechanism of gas-material-coupled unsteady flow causing aerodynamic noise. However, it is difficult to clarify the mechanism through measurement. Therefore, the following topics are studied in this article. First, a full-field transient numerical simulation of the gas and solid particulates’ unsteady flow inside the impeller blower was carried out using a dense discrete phase model and a large eddy simulation turbulence model. Second, based on the Ffowcs Williams–Hawkins equation, the aerodynamic noise of the impeller blower of the straw threshing machines was numerically calculated. Finally, the numerical results were verified by aerodynamic noise test. The results indicate that (1) sound pressure level at the inlet of the impeller blower is the highest, mainly at 100 Hz, which is the fundamental frequency of the rotating impeller, while the sound pressure level at the fourth harmonic frequency of 400 Hz is the main source of the outlet. The total sound pressure level at the inlet is greater than that at the outlet. It is concluded that the dipole source of the rotating impeller is the main noise source, which was generated by the interaction of blade with the air and material as the impeller rotated. Also, acoustic attenuation, acoustic resonance, and impact noise of material and machinery play important roles in aerodynamic noise distribution. (2) The test and simulation results show good agreement, so the numerical model of aerodynamic noise is reliable. This study will provide a reference for the structural and acoustic optimization design of impeller blowers and their integration into threshing machines.

Low speed longitudinal aerodynamic, static stability and performance analysis of a hypersonic waverider

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing was conducted in the University of Sydney 4 foot by 3 foot low speed facility, while propulsion testing of the vehicle-integrated electric ducted fan was completed in the 7 foot by 5 foot tunnel. Motor thrust settings were tested for 8 lithium polymer cells connected serially drawing between 5 and 25 amperes. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between −5 and 25 degrees and elevon deflections between −10 and 10 degrees. Results show the aerodynamics is dominated by leading edge flow separation and vortex lift. At a centre of gravity location of 44.4% of the vehicle length, stability is observed up to 22 degrees angle of attack. Past this point, instability occurs due to vortex breakdown. The centre of gravity aft stability limit was found at 53.1% of the vehicle length. Overall, good agreement is seen between simulation and tunnel data, validating the modelling methods used. The low speed demonstrator can achieve trimmed flight from 12 m/s, but is only speed stable above 19 m/s. A cruise speed of 19 m/s is selected and can be attained with approximately −9.2 degrees of elevon and 7.1 degrees AoA for a centre of gravity location of 44.4%. Shifting the centre of gravity aft can reduce the trim angle of attack to below 6 degrees with −4 degrees elevon deflection. Take-off and landing can be achieved at 15 m/s between 9.8 and 12 degrees angle of attack, depending on centre of gravity configuration. A maximum climb rate of 2.1 m/s is predicted at 16.3 m/s based on the power settings tested. Overall, the results show the aircraft satisfies stability and performance requirements in the longitudinal axis.

Aerodynamic Stability of Bridge Structures

Large-span bridges, which are flexible structures, are more susceptible to the wind influence. At the same time, it is necessary to take into account the effect of snow drift and automobile traffic on the stability of the superstructure. As the object of research a metal continuous beam bridge with two parallel independent span structures was chosen. The program of aerodynamic test at the wind-tunnel was given at the paper. The paper presents the test results for the most interesting angles of attack from the aerodynamic point of view. Based on the test results, it was established that it is impossible to speak unequivocally about the effect of snow deposits on the aerodynamic stability of the span. The presence of automobile traffic on the span under study excludes all possible phenomena of aerodynamic instability, for all the flow directions considered.

Aerodynamic and aeroelastic wind tunnel model tests of overhead power lines in triangular configuration under different icing conditions

This paper describes the experimental model tests conducted in the boundary layer wind tunnel of the Wind Engineering Laboratory of Cracow University of Technology. The tests were focused on overhead power line conductors arranged in triangular bundles under different types of icing. Five representative cases of snow, ice and rime/frost loads were assumed on the basis of examples defined in literature and field studies. A dimensional analysis was conducted for the case studies. The experimental model tests were conducted in two independent series. Each series required sectional models of different features. The results of the first series were in the form of mean aerodynamic coefficients Cx, Cz and Cm for selected cases of snow, ice and rime/frost conductors covers. On this basis, aerodynamic interferences of overhead line conductors were determined. The model tests were performed on a rigid sectional model of conductors. The second series was aimed at the identification of aeroelastic phenomena caused by interference of the conductors. As a result, the critical velocity of conductors galloping and wake galloping for selected cases of snow, ice and rime/frost covers was determined. For this series of tests, a sectional aeroelastic model (rigid sectional model of each cable with flexible supports at the ends) of the three-cable bundled conductors was made.

Effect of Nozzle Exit Wear on the Fluid Flow Characteristics of Supersonic Oxygen Lance

Supersonic jet characteristics of oxygen lance nozzles have a significant influence on smelting; however, presently, little research has been carried out to investigate the influence of wear on the jet characteristics at the nozzle exit. A numerical model and aerodynamic testing platform were developed to analyze supersonic jet characteristics under different inlet pressures and wear levels at the nozzle exit. The numerical model was first validated by comparing the numerical results with the measured data of the aerodynamic testing experiment. Then, the effects of the inlet pressure and nozzle exit wear on the jet velocity and degree of aggregation were studied. An increase in the nozzle inlet pressure is conducive to an increase in jet velocity but also causes earlier jet convergence. An increase in the nozzle exit wear results in the faster attenuation of jet velocity, not only reducing the jet velocity but also leading to an earlier convergence point for each jet. The results of this study can provide theoretical support for the design of an oxygen lance nozzle and process optimization of smelting in industrial application.

Effect of moving ground on the aerodynamics of a generic automotive model: The DrivAer-Estate

With the recent trend to require automotive aerodynamic testing in wind tunnels with rolling-road floors, this study investigates the impacts of the ground configuration on the aerodynamic characteristics of a generic estate-type vehicle – the DrivAer-Estate. This is based on a comparison between time-dependent computational predictions for two configurations: one with a stationary ground with stationary wheels, and another with a moving ground and rotating wheels. This study quantifies the time-averaged flow structures, wake dynamics, surface pressure distributions and aerodynamic loadings, and by comparing these for the two cases. This study determines the distinct flow features and the mechanism of how different ground simulations affect the aerodynamic characteristics. Predictions using an Improved Delayed Detached Eddy Simulation (IDDES) model are validated where possible against time-mean wind-tunnel measurements, providing confidence in the simulation results. Indeed, the results show that due to the distinct flow features generated by estate-type geometries, the ground configuration only locally alters the flow field in close proximity to the ground, and therefore its impact on the flow near the automobile surfaces and in the wake is limited. Regarding the aerodynamic loadings, only the underbody surface pressure is found to be sensitive to the ground simulation, which leads to a variation in the lift coefficient by a factor of approximately two. However, the impact on the drag prediction is minimal, with the two drag coefficient predictions within 3% of each other, and consistent within the range of values from previous wind-tunnel tests.

Effect of Various Surface Coatings on De-Icing/Anti-Icing Fluids Aerodynamic and Endurance Time Performances

The Anti-icing Materials International Laboratory (AMIL) has been testing SAE AMS1424 and AMS1428 ground de-icing/anti-icing fluids for more than 30 years. With the introduction of new surface coatings and their investigation as potential passive ice protection systems, or for hybrid use with other methods, it is important to understand their interaction with the ground de-icing/anti-icing fluids prior to applications on aircraft. In this study, five different surface coatings, both commercially available and under development, have been tested under two current test methods used to qualify the ground de-icing/anti-icing fluids: The Water Spray Endurance Test (WSET) and the Aerodynamic Acceptance Test (AAT). The tests were performed on three existing commercial de-icing/anti-icing fluids. The results have shown that the coatings tested in this study can considerably reduce the endurance time of the fluids and affect their ability to spread and wet the test surface. Superhydrophobic 1 coating also reduced the aerodynamic penalties created by the Ref. Fluid. Surface coatings, no matter their nature, can impact the performances and behaviour of the fluids and should be thoroughly tested before their use in the industry. The conclusions and methodology of this study were used in the development of sections of the SAE AIR6232 Aircraft Surface Coating Interaction with the Aircraft Deicing/Anti-Icing Fluids standard.

Recent advances and test processes in automotive and motorsports aerodynamic development

This article highlights the advances in the aerodynamic development and test processes of both road and motorsports cars over the last two decades, including explaining the main driving forces behind this evolution. The relentless and continuous drive to improve efficiency and correlation between computational fluid dynamics, real-time simulation, wind tunnel testing, and the track is explained. Key enabling technologies are described, such as: continuous motion systems; high-speed data acquisition systems; steel moving belt ground planes with under floor load cells; on-demand robotic particle image velocimetry; pneumatic model tyres with integral sidewall and contact patch deflection systems; driver simulators and rapid prototyped rake systems for track cars. Finally, as aerodynamicists attempt to simulate and test within ever more complex and realistic environments potential future directions and emerging trends are outlined, including gusts, aeroelasticity, adaptive cooling, and cornering.

Applications of surrogate-assisted and multi-fidelity multi-objective optimization algorithms to simulation-based aerodynamic design

Purpose The purpose of this work is to apply and compare surrogate-assisted and multi-fidelity, multi-objective optimization (MOO) algorithms to simulation-based aerodynamic design exploration. Design/methodology/approach The three algorithms for multi-objective aerodynamic optimization compared in this work are the combination of evolutionary algorithms, design space reduction and surrogate models, the multi-fidelity point-by-point Pareto set identification and the multi-fidelity sequential domain patching (SDP) Pareto set identification. The algorithms are applied to three cases, namely, an analytical test case, the design of transonic airfoil shapes and the design of subsonic wing shapes, and are evaluated based on the resulting best possible trade-offs and the computational overhead. Findings The results show that all three algorithms yield comparable best possible trade-offs for all the test cases. For the aerodynamic test cases, the multi-fidelity Pareto set identification algorithms outperform the surrogate-assisted evolutionary algorithm by up to 50 per cent in terms of cost. Furthermore, the point-by-point algorithm is around 27 per cent more efficient than the SDP algorithm. Originality/value The novelty of this work includes the first applications of the SDP algorithm to multi-fidelity aerodynamic design exploration, the first comparison of these multi-fidelity MOO algorithms and new results of a complex simulation-based multi-objective aerodynamic design of subsonic wing shapes involving two conflicting criteria, several nonlinear constraints and over ten design variables.

Research on Free Jet Test Technology

Aerodynamic thermal ground test can not completely simulate flight conditions, and there is no simple and clear similarity criterion as aerodynamic test. In practical application, it is often to grasp the local flow characteristics of materials or structures and use ground test equipment to simulate their main thermal environment parameters. Therefore, according to the thermal environment characteristics of different parts of the aircraft, a variety of arc heating test techniques have been developed. For example, free jet test technology has been developed for material test of simplified model and assessment test of small-scale components. It effectively solves some problems of thermal protection test examination.

Comparison of Support Methods for Static Aerodynamic Testing and Validation of a Magnetic Suspension and Balance System

Comparison of Support Methods for Static Aerodynamic Testing and Validation of a Magnetic Suspension and Balance System

Study on Testing Environment Simulation Method for Thermal Flux Density of Aerothermal

This paper presents the use of forced convection heat transfer approach to near-space thermal environment of hypersonic aerodynamic ground simulation test method for surface heat flux with a great gradient and temperature gradient of the tip wedge (rn=1.5mm) shape component level thermal test. In the test device test section, two different high subsonic speed airflow were nested within each of the two vents from the exhaust, the impact of the specimen heated to test sharp wedge surface heat flow and temperature distribution in line with a hypersonic flight state aerodynamic heat distribution patterns. Numerical results show that under this scenario, the specimen rear stagnation point heat flux and heat flux can be adjusted two ways to adjust the air flow; test methods within a certain accuracy-related parts for the superb aerodynamic vehicle thermal environment simulation.

Review of research on high-speed railway aerodynamics in China

AbstractHigh-speed railway aerodynamics is the key basic science for solving the bottleneck problem of high-speed railway development. This paper systematically summarizes the aerodynamic research relating to China’s high-speed railway network. Seven key research advances are comprehensively discussed, including train aerodynamic drag-reduction technology, train aerodynamic noise-reduction technology, train ventilation technology, train crossing aerodynamics, train/tunnel aerodynamics, train/climate environment aerodynamics, and train/human body aerodynamics. Seven types of railway aerodynamic test platform built by Central South University are introduced. Five major systems for a high-speed railway network—the aerodynamics theoretical system, the aerodynamic shape (train, tunnel, and so on) design system, the aerodynamics evaluation system, the 3D protection system for operational safety of the high-speed railway network, and the high-speed railway aerodynamic test/computation/analysis platform system—are also introduced. Finally, eight future development directions for the field of railway aerodynamics are proposed. For over 30 years, railway aerodynamics has been an important supporting element in the development of China’s high-speed railway network, which has also promoted the development of high-speed railway aerodynamics throughout the world.

Experimental Aerodynamic Simulation of a Scallop Ice Accretion on a Swept Wing

<div class="section abstract"><div class="htmlview paragraph">Understanding the aerodynamic impact of swept-wing ice accretions is a crucial component of the design of modern aircraft. Computer-simulation tools are commonly used to approximate ice shapes, so the necessary level of detail or fidelity of those simulated ice shapes must be understood relative to high-fidelity representations of the ice. Previous tests were performed in the NASA Icing Research Tunnel to acquire high-fidelity ice shapes. From this database, full-span artificial ice shapes were designed and manufactured for both an 8.9%-scale and 13.3%-scale semispan wing model of the CRM65 which has been established as the full-scale baseline for this swept-wing project. These models were tested in the Walter H. Beech wind tunnel at Wichita State University and at the ONERA F1 facility, respectively. The data collected in the Wichita St. University wind tunnel provided a low-Reynolds number baseline study while the pressurized F1 facility produced data over a wide range of Reynolds and Mach numbers with the highest Reynolds number studied being approximately <i>Re</i> = 11.9×10<sup>6</sup>. Past work focused on only three different fidelity variations for ice shapes based on multiple icing conditions. This work presents a more detailed investigation into several fidelity representations of a single highly three-dimensional scallop ice accretion. Sensitivity to roughness size and application technique on a low-fidelity smooth ice shape is described. The data indicate that the aerodynamic performance is not especially sensitive to the grit variations. An ice accretion code was also used to generate ice shapes for aerodynamic testing and comparisons. These ice shapes have a general appearance like the low-fidelity smooth ice shapes, but in this case, the computer-generated ice shape is significantly smaller. As such, the impact of that ice shape on the aerodynamic performance of the wing is reduced compared to the smooth ice shape based on the icing experiment for those same conditions. Spanwise discontinuities were also introduced to a low-fidelity ice shape in an attempt to quantify the impact of those variation in the high-fidelity ice shape. While the lift data indicate good agreement between the high-fidelity ice shapes and the low-fidelity ice shapes with spanwise discontinuities, a closer investigation of the data suggests potential, significant differences in the flowfield. These results were similar at both facilities over the wide range of test conditions utilized.</div></div>

Construction of bi-layer biluminophore fast-responding pressure sensitive coating for non-contact unsteady aerodynamic testing

Abstract Herein we report on a biluminophore fast-responding pressure sensitive coating with a bi-layer structure prepared by a non-sensitive reference base paint and subsequently a classic polymer-ceramic pressure sensitive paint (PSP). The coating procedure is fully sprayable and allows the separation of the two luminophores in each layer to prevent their interference that may affect the pressure responsibility. The major advance is the use of sol-gel process of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) to make the bottom reference layer which ensures the spreading and affinity of the top PSP, composed of a room-temperature vulcanizing silicone rubber (RTV), so that very thin PSP layer, i.e. less than 5 μm, was achieved. Besides, silane-functionalized carbon dots (CDs) was selected as the reference probe, for it could be well-incorporated with the TEOS/MTES matrix, and gained high loading level and hence strong luminescence of the basecoat to overcome the attenuation effect of the top PSP layer. The resultant biluminophore bi-layer fast-responding PSP (denoted as Fast bi-PSP) showed two completed separated emissions with λmax at 430 and 600 nm for the incorporated CDs and the oxygen sensitive ruthenium complex dye, which enables the utility of intensity ratio from blue and red luminescence for the measurement of surface pressure by following Stern-Volmer relationship. Using a shock tube, the response time of the Fast bi-PSP coating was determined to be 0.4–0.6 ms according to the chemical composition. The ability of the coating for monitoring the dynamic evolution of full-field surface pressure was demonstrated on sample plates at attack angles of 0° and 5°. Our work suggests a facile but efficient way for the future design of self-referenced photoluminescent non-contact surface pressure sensing systems.

Aerodynamic interference test of quad tilt rotor aircraft in wind tunnel

There is an obvious aerodynamic interference problem that occurs for a quad tilt rotor in near-ground hovering or in the conversion operating condition. This paper presents an aerodynamic interference test of the quad tilt rotor in a wind tunnel. A 1:35 scale model of the quad tilt rotor is used in this test. To substitute for the ground, a moveable platform is designed in a low-speed open-loop wind tunnel to simulate different flight altitudes of the quad tilt rotor in hovering or forward flight. A rod six-component force balance is used to measure the loads on the aircraft, and the flow field below the airframe is captured using particle image velocimetry. The experimental results show that the ground effect is significant when the hover height above the ground is less than the rotor diameter of the quad tilt rotor aircraft, and the maximum upload of the airframe is approximately 12% of the total vertical thrust with the appearance of obvious fountain flow. During the conversion operating condition, the upload of the airframe is reduced compared with that in the hovering state, which is affected by rotor wake and incoming flow. The aerodynamic interference test results of the quad tilt rotor aircraft have important reference value in power system selection, control system design, and carrying capacity improvement with the advantage of ground effect.

Aerodynamic Design and Testing of an Imbedded Forward Swept Rotor in a Two-Stage Transonic Fan

Previous experimental and analytical studies comparing the performance of transonic swept rotors in single and multistage fans have demonstrated the potential of large improvements in clean inlet performance and substantial improvements in fan sensitivity with inlet distortion with forward swept blading. A two-stage, low-aspect ratio transonic fan investigation was previously conducted in the Air Force’s Compressor Research Facility, in two builds on a back-to-back test basis, using a radial and a forward swept stage 1 blade. While the forward swept stage 1 blade configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion, the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1. To address this measured overall performance shortfall, this paper reports on the design of a new second stage blade tested in the same two-stage fan rig with the forward swept stage 1 blade configuration. The new second stage blade was designed with forward sweep to improve efficiency and operability while replicating the baseline radial rotor 2’s aerodynamic design conditions within the same flow path. The design point requirements of the forward swept rotor 2 were selected to preserve the internal stage matching with the radially stacked rotor 2. As the new stage 2 blade had to fit within the existing radial rotor 2’s physical envelope, the new blade was designed with forward sweep through lean only, which proved to be quite challenging from a mechanical growth and deflection view point. The first attempt to run the fan rig with the new stage 2 blade resulted in a leading-edge tip rub during a part speed stall event. However, even with this unfortunate event, fan mapping test results with clean inlet from part speed to 97.5% design speed showed a significant improvement in overall fan efficiency and stall margin, validating the hypothesis that in the earlier tests stage 2 was indeed the limiting stage that prevented the fan from reaching its overall performance goals. Based on this experience and the test data acquired with unstable leading-edge tip rubs during stall deflections with forward swept airfoils leaned in the direction of rotation, a process was developed to determine the acceptability criteria of such blading.

Evaluation of Voice Quality in Patients With Vocal Fold Polyps: The Size of a Polyp Matters or Does it?

ObjectiveThis study aimed to investigate the correlation between morphological features of vocal fold polyps (VFPs) and subjective/objective voice parameters. MethodsPerceptual evaluations, aerodynamic and acoustic tests were performed on 47 patients with VFPs. Still images were captured from video and the morphological features associated with the size of VFP were quantified. To reveal the correlation between size-related morphological features (length of polyp base, the ratio of polyp base to vocal fold length, glottal gap area) and objective/subjective parameters of voice, Pearson's and Spearman's tests were carried out. ResultsThis cohort was composed of 30 (63.8 %) male and 17 (36.2%) female patients with the mean age of 45.2 years and 41.3 years, respectively. No correlation was found between the morphological features of VFPs and any of perceptual, aerodynamic and acoustic voice parameters. ConclusionsOur findings indicated that controversies still exist regarding the role of vocal fold polyp morphology in clinical decision making.

Fast Track Integration of Computational Methods with Experiments in Small Wind Turbine Development

In general, standard aerodynamic design is divided into two paths—numerical analysis and empirical tests. It is crucial to efficiently combine both approaches in order to entirely fulfill the requirements of the design process as well as the final product. An effective use of computational analysis is a challenge, however it can significantly improve understanding, exploring and confining the search for optimal product solutions. The article focuses on a rapid prototyping and testing procedure proposed and employed at the Institute of Turbomachinery, Lodz University of Technology (IMP TUL). This so called Fast Track approach combines preparation of numerical models of a wind turbine rotor, manufacturing of its geometry by means of a 3D printing method and testing it in an in-house wind tunnel. The idea is to perform the entire procedure in 24 h. The proposed process allows one to determine the most auspicious sets of rotor blades within a short time. Owing to this, it significantly reduces the amount of individual subsequent examinations. Having fixed the initial procedure, it is possible to expand research on the singled-out geometries. The abovementioned observations and the presented overview of the literature on uses of 3D printing in aerodynamic testing prove rapid prototyping as an innovative and widely-applicable method, significantly changing our approach to experimental aerodynamics.

Hydrodynamic Features of the Flow Downstream from the Mixing Spacer Grid in a Kvadrat Fuel Assembly in PWRs

The experimental investigation of local hydrodynamic characteristics of the coolant flow downstream of a mixing spacer grid (MSG) in characteristic regions of a Kvadrat fuel assembly in PWRs was performed. The importance of this investigation is due to the fact that MSGs of interest can enhance heat-and-mass transfer. Finding the best design of the grid is required for corroboration of the thermal engineering reliability and operability of the PWR core. The paper presents a description of the test facility and a model of a fuel assembly fragment, the investigation procedure, and discussion of the results. The experiments were performed in the aerodynamic test facility on a scaled model of a fragment of a Kvadrat fuel assembly by simulating the water coolant flow using an air flow according to the hydrodynamic similarity theory. Within the scope of the investigation, the transverse velocity fields in the coolant flow were studied in the characteristic cross-sections of the fuel assembly. The transverse velocity distribution was measured with a five-channel pneumometric probe that can determine the module and direction of a flow velocity vector at an investigated point. The experimental results are presented in the form of distribution of relative transverse velocity downstream of MSG in the characteristic regions of the fuel assembly, such as standard cells, guide channel, and a gap between fuel rods. Based on the experimental data, the coolant flow features have been revealed, and the regularities in the development of transverse velocity field downstream of the mixing spacer grid under investigation have been determined. These experimental data are required for assessment of the mixing spacer grid effectiveness, verification of 3D CFD-programs, and applicable cell-by-cell codes for calculation of a PWR core with a Kvadrat fuel assembly.