Aerodynamic Data Research Articles

Experimental study on performance of helium high pressure compressors of HTR-10GT

In the six candidate types of the fourth-generation nuclear power system, the Helium Gas Turbine System (HGTS) will be the ideal power conversion system for both the Modular High Temperature Gas-cooled Reactor (Modular HTGR) and the Gas-cooled Fast Reactor. The main advantages of HGTS are the compact and simple configuration and the high power-generation efficiency by taking advantage of high temperature heat source. At present, one of the main research contents of HGTS in China is helium compressors in HTR-10GT project. Previous researches showed that the aerodynamic performance of the helium compressors was one of the key factors of the efficiency of HGTS and had direct influences on the efficiency of the system. With different working fluids, features of helium compressors are different from conventional compressors. There were very limited experimental and theoretical studies in the research field of helium compressors. In this paper, a performance test system for the full-stage and full-scale helium compressors was employed to test and investigate the performance of the helium compressors of HTR-10GT, including pressure ratio, efficiency and surge and block boundaries. The performance of the high-pressure compressor (HPC) was measured at rated conditions and at different rotating speeds and different inventory levels. The results showed that the pressure ratio of the HPC satisfied the requirements of the HGTS, and the efficiency of the HPC was below expectation. The experimental study represented the applicability of the helium compressor design methods and provided the key aerodynamic performance data for future studies, such as off-design conditions, studies on compressor design methods and further improvement on the performance of the helium compressors.

The Comparison of Aerodynamic Performance Data Acquired From Thermal Measurements and a Torquemeter on a Compressor Impeller

Full-thermal heat-soak of machinery is vital for acquiring accurate aerodynamic performance data, but this process often requires significant testing time to allow all facility components to reach a steady-state temperature. Even still, there is the potential for heat loss in a well-insulated facility, and this can lead to inaccurate results. The implementation of a torquemeter to calculate performance metrics, such as isentropic efficiency, has two potential advantages: (1) the method is not susceptible to effects due to thermal heat loss in the facility, and (2) a torquemeter directly measures actual torque, and thus work, input, which eliminates the need to fully heat-soak to measure the actual enthalpy rise of the gas. This paper presents a comparison of aerodynamic performance metrics calculated both from data acquired with thermal measurements as well as from a torquemeter. These tests were conducted over five speedlines for a shrouded impeller in the Southwest Research Institute Single Stage Test Rig facility. Isentropic efficiency calculated from the torquemeter was approximately 1–2 efficiency points lower than the isentropic efficiency based on thermal measurements. This corresponds to approximately 0.5–1 °C in heat loss in the discharge collector and piping. Furthermore, observations from three full-thermal heat-soak points indicate the significant difference in time required to reach steady-state performance within measurement uncertainty tolerances between the torque-based and thermal-based methods. This comparison, while largely suspected, has not yet been studied in previous publications.

Experimental study on performance of helium low pressure compressor of HTR-10GT

Helium Gas Turbine System (HGTS) has compact and simple configuration, and can make full use of high temperature heat source to achieve high power generation efficiency. It will be the desirable power conversion system for the Modular High Temperature Gas-cooled Reactor (Modular HTGR) in the future. But there are some technical challenges to be solved for HGTS, including helium compressor and active magnetic bearings, etc. Helium compressor is key component for HGTS. Its aerodynamic performance had direct influences on the efficiency of the HGTS. Its features are different from those of conventional air compressors or gas turbines due to the different working fluids. The experimental and theoretical studies on helium compressors were very limited. In this paper, a performance test system for HTR-10GT project was established for the full-stage and full-scale helium compressors. Performance of low-pressure compressor (LPC) of HTR-10GT was tested and investigated on this test system. The pressure ratio and efficiency of the LPC were obtained at rated conditions and at different rotating speed, different inventory level. Surge and block boundaries of LPC were also explored. The results showed that the performance of LPC satisfied the design requirements. And the experimental study in the paper verified the validity and effectiveness of the design methods of the helium compressors at the LPC conditions, and provided the key aerodynamic performance data for further studies, such as off-design conditions, inventory control and load rejection control.

Energy-Saving Algorithm of Automatic Control of Compulsory Passenger Carrier Landing. Part 1

The task was to develop an automatic landing system (ALS) for a passenger carrier that can be externally activated and excludes the possibility of the crew’s interference into the landing process, for example, when a carrier alters its nominal course or there is no contact with the crew. The air crush history saw a lot of cases that could have been prevented if the planes had had an ALS system and airports had had possibilities to activate that system and suspend the crew from flight control. One of such unforgettable examples is the New-York tragedy of September 11, 2001. State-of-the-art technology allows solving the problem of automatic carrier landing. The most remarkable example demonstrating solution of this problem is the automatic landing of the Buran orbiter 30 years ago on November 15, 1988. The article consists of two sections. The first section of the article deals with conditions of effective solution of autoland problem. It describes in short, the flight modes during automatic landing control. To solve the problem of automatic longitudinal control in the most crucial final landing mode, the author proposes an energy-saving control algorithm that provides control in the mode of negative feedback. The system status vector comprises six parameters: range, altitude, pitch angle, and their first-order derivatives. The control algorithm is developed for the Tupolev TU-154M airliner. In development of the algorithm, the following assumptions were used: a) a linear model of dependence of aerodynamic data on the angle of attack; b) a linear model of programmed switch of engine thrust to the idle mode on the interval of 3 seconds from the beginning of the flareout; c) a pitch angular acceleration, occurring at elevator rate reversal, as a control signal; d) the frequency of the control algorithm operation equal to 200 Hz. The second section further analyzes characteristics of the energy-saving algorithm of automatic control of compulsory passenger carrier landing during the final landing phase, which was developed in the first section. The author developed a model program of control and mathematically modeled the carrier landing phases. When switching from one phase to another, the motion parameters were concatenated so that the final motion parameters of the previous phase became the initial motion parameters of the next phase. The author also studied the influence of errors in aerodynamic data on the landing conditions. The modeling revealed that if a pitch deflection direction is used for the determination of phases, then in a general case, the landing mode consists not of two traditionally determined phases, but of the following three: pitch angle increase (flareout), pitch angle decrease (float), and again, pitch angle increase (this phase is called ‘maintenance’). The necessity to introduce the third phase is determined by the presence of errors in the aerodynamic data of the airplane. On the whole, it is confirmed that the energy saving control algorithm provides successful solution of the problem of automatic landing of a passenger carrier at its final flight phase. At that, it is determined that the landing mode does not exceed 5s.

Application of Machine Learning Methods to Interpolation of Aircraft Aerodynamic Data

Application of Machine Learning Methods to Interpolation of Aircraft Aerodynamic Data

Airfoil Optimization Design Based on the Pivot Element Weighting Iterative Method

Class function/shape function transformation (CST) is an advanced geometry representation method employed to generate airfoil coordinates. Aiming at the morbidity of the CST coefficient matrix, the pivot element weighting iterative (PEWI) method is proposed to improve the condition number of the ill-conditioned matrix in the CST. The feasibility of the PEWI method is evaluated by using the RAE2822 and S1223 airfoil. The aerodynamic optimization of the S1223 airfoil is conducted based on the Isight software platform. First, the S1223 airfoil is parameterized by the CST with the PEWI method. It is very significant to confirm the range of variables for the airfoil optimization design. So the normalization method of design variables is put forward in the paper. Optimal Latin Hypercube sampling is applied to generate the samples, whose aerodynamic performances are calculated by the numerical simulation. Then the Radial Basis Functions (RBF) neural network model is trained by these aerodynamic performance data. Finally, the multi-island genetic algorithm is performed to achieve the maximum lift-drag ratio of S1223. The results show that the robustness of the CST can be improved. Moreover, the lift-drag ratio of S1223 increases by 2.27% and the drag coefficient decreases by 1.4%.

An experimental study on the aerodynamic performance degradation of a wind turbine blade model induced by ice accretion process

Abstract An experimental study was conducted to characterize aerodynamic performance degradation of wind turbine blades induced by dynamic ice accretion process. The experimental study was performed in an Icing Research Tunnel with a turbine blade model under a typical glaze icing condition. Ice structures were found to accrete rapidly over both the upper and lower surfaces of the blade model after starting the ice accretion experiment. Irregular-shaped ice structures were found to disturb the airflow around the blade model greatly, resulting in large-scale flow separations and shedding of unsteady vortex structures from the ice accreting surface. The aerodynamic performance of the blade model was found to degrade significantly. The performance degradation induced by the ice accretion was found to be a strong function of the angle of attack of the blade model with more significant degradations at lower angles of attack. For the test case at the angle of attack of 5.0°, while the lift decreases to only ∼12% of its original value after 600 s of the ice accretion experiment, the drag was found to increase 4.5 times correspondingly. The detailed flow field measurements were correlated with the aerodynamic force data to elucidate the underlying physics.

Analysis and optimization of morphing wing aerodynamics

PurposeThe purpose of this paper is to present a method for analysis and optimization of morphing wing. Moreover, a numerical advantage of morphing airfoil wing, typically assessed in simplified two-dimensional analysis is found using higher fidelity methods.Design/methodology/approachBecause of multi-point nature of morphing wing optimization, an approach for optimization by analysis is presented. Starting from naïve parametrization, multi-fidelity aerodynamic data are used to construct response surface model. From the model, many significant information are extracted related to parameters effect on objective; hence, design sensitivity and, ultimately, optimal solution can be found.FindingsThe method was tested on benchmark problem, with some easy-to-predict results. All of them were confirmed, along with additional information on morphing trailing edge wings. It was found that wing with morphing trailing edge has around 10 per cent lower drag for the same lift requirement when compared to conventional design.Practical implicationsIt is demonstrated that providing a smooth surface on wing gives substantial improvement in multi-purpose aircrafts. Details on how this is achieved are described. The metodology and results presented in current paper can be used in further development of morphing wing.Originality/valueMost of literature describing morphing airfoil design, optimization or calculations, performs only 2D analysis. Furthermore, the comparison is often based on low-fidelity aerodynamic models. This paper uses 3D, multi-fidelity aerodynamic models. The results confirm that this approach reveals information unavailable with simplified models.

A aerodinâmica das consoantes nasais [m] e [n] do português brasileiro

Este estudo tem como objetivo uma caracterização aerodinâmica das consoantes nasais [m] e [n] do português brasileiro, com o uso de tecnologias computadorizadas e coleta simultânea de dados acústicos e aerodinâmicos, em uma perspectiva dinâmica de produção da fala. As gravações envolveram cinco adultos, com idades entre 25 e 52 anos, três do sexo feminino e dois do sexo masculino. O corpus incluiu 20 logatomas em frases-veículo, variando o contexto de tonicidade e o da vogal precedente. Os dados de fala foram coletados por meio da Estação EVA (Evaluation Vocale Assistée) e do piezoelétrico. Dos dados advindos da Estação EVA, foram investigadas configurações de curvas de fluxo aéreo oral (FAO) e de fluxo aéreo nasal (FAN); e dos dados advindos do piezoelétrico, foram analisados valores das curvas de FAN. Os resultados indicaram, para ambos os sexos, semelhanças entre as consoantes [m] e [n]: muito baixa amplitude nas curvas de FAO, indicando oclusão na passagem de ar pela cavidade oral; e curvas de FAN com configuração plana em sua extensão e com maior amplitude em relação às vogais adjacentes. Assim, o comportamento aerodinâmico do FAN na produção das consoantes [m] e [n] permitiu a inferência articulatória de que o gesto vélico dessas consoantes seja formado por três tempos: abertura, platô e fechamento. Ainda, foram confirmadas diferenças significativas entre parâmetros aerodinâmicos relativos às consoantes [m] e [n], quanto ao contexto de tonicidade e ao da vogal precedente. As características aerodinâmicas apontaram, portanto, para a natureza dinâmica das consoantes nasais do português brasileiro.

NON-LINEAR EFFECTS OF AIRFOIL FORCE DATA ON DESIGN PERFORMANCE OF A LOW-REYNOLDS NUMBER PROPELLER

Over the last three decades and a half, there has been huge effort to develop high performance propellers suitable for flight in the rarefied Mars atmosphere. This paper describes work undertaken in validating vortex theory in the design of a 2-bladed heavily loaded propeller with a solidity of ≈0.25 and chord based Reynolds number of ≈60k (calculated at 75% radius) at design point. The design was based on minimum induced propeller losses and lifting line theory. 2D-airfoil experiment data of SD7037 collected at Reynolds number of 60k was used for the entire blade design. At design advance ratio, more than 50% of the entire blade radius operated between 40k – 60k Reynolds numbers. A design goal of the propeller was to minimize variation in Reynolds number from hub to tip radius. Wind tunnel tests carried out at Kyushu Institute of Technology were performed in two (2) ways: constant angular velocity and changing airflow velocity over the propeller, and constant airflow velocity and changing propeller angular velocity. The fabricated propeller showed good agreement in efficiency for both test cases. However, considerable discrepancy was observed between theory and experiment in thrust and power. Investigation showed that non-linearity associated with airfoil aerodynamic data not captured by linearization result in a less representative modeling of the airfoil force coefficient and consequently, discrepancy in propeller performance between theory and experiment.

Development of Model Predictive Controller for a Tail-Sitter VTOL UAV in Hover Flight.

This paper presents a model predictive controller (MPC) for position control of a vertical take-off and landing (VTOL) tail-sitter unmanned aerial vehicle (UAV) in hover flight. A ‘cross’ configuration quad-rotor tail-sitter UAV is designed with the capabilities for both hover and high efficiency level flight. The six-degree-of-freedom (DOF) nonlinear dynamic model of the UAV is built based on aerodynamic data obtained from wind tunnel experiments. The model predictive position controller is then developed with the augmented linearized state-space model. Measured and unmeasured disturbance model are introduced into the modeling and optimization process to improve disturbance rejection ability. The MPC controller is first verified and tuned in the hardware-in-loop (HIL) simulation environment and then implemented in an on-board flight computer for real-time indoor experiments. The simulation and experimental results show that the proposed MPC position controller has good trajectory tracking performance and robust position holding capability under the conditions of prevailing and gusty winds.

Impact of Flow Unsteadiness on Steady-State Gas-Path Stagnation Temperature Measurements

Steady-state stagnation temperature probes are used during gas turbine engine testing as a means of characterizing turbomachinery component performance. The probes are located in the high-velocity gas-path, where temperature recovery and heat transfer effects cause a shortfall between the measured temperature and the flow stagnation temperature. To improve accuracy, the measurement shortfall is corrected post-test using data acquired at representative Mach numbers in a steady aerodynamic calibration facility. However, probes installed in engines are typically subject to unsteady flows, which are characterized by periodic variations in Mach number and temperature caused by the wakes shed from upstream blades. The present work examines the impact of this periodic unsteadiness on stagnation temperature measurements by translating probes between jets with dissimilar Mach numbers. For conventional Kiel probes in unsteady flows, a greater temperature measurement shortfall is recorded compared to equivalent steady flows, which is related to greater conductive heat loss from the temperature sensor. This result is important for the application of post-test corrections, since an incorrect value will be applied using steady calibration data. A new probe design with low susceptibility to conductive heat losses is therefore developed, which is shown to deliver the same performance in both steady and unsteady flows. Measurements from this device can successfully be corrected using steady aerodynamic calibration data, resulting in improved stagnation temperature accuracy compared to conventional probe designs. This is essential for resolving in-engine component performance to better than ±0.5% across all component pressure ratios.

Slipstreaming in Gravity Powered Sports: Application to Racing Strategy in Ski Cross.

The principles of slipstreaming or drafting are very well known in muscle-powered sports, but unknown in gravity-powered sports. Typical examples of gravity-powered sports, where several athletes are racing against each other, are ski-cross and snowboard-cross. The aim of this research is to investigate the effectiveness and practical applicability of slipstreaming in ski-cross. A glide model consisting of leading and trailing skiers was developed and used with existing aerodynamic drag and lift data sets from wind tunnel tests. Different scenarios were tested as to their effect on slipstreaming, such as variation of speed, skiers' mass, slope angle, air density, and racing posture (high/low tucked position). The higher the trailing skier's inertial force and acceleration is compared to the leading one, the quicker the trailing skier can catch up. Making more ground up on the racing track is related to higher speed, less body mass (of both skiers), flatter slope angle, denser air, and higher racing posture (high tucked position of both skiers). The glide model presented in this research can be used in the future for testing of slope track design, provided that precise dimensions of terrain features are available.

Test of aero-heating in hypersonic non-equilibrium flow and numerical simulation study

In the design of hypersonic vehicle thermal protection, precise prediction on the non-equilibrium aerodynamic heating in condition of hypersonic flow has been recognized as the difficult and hot topic in the current academic and engineering field. In this paper, a simple spherical column thermal model was designed. The surface catalytic properties of the model and plug-type calorimeter were changed by sputtering Au and SiO2 on the surface. In the arc tunnel, a hypersonic non-equilibrium flow aerodynamic heating test was carried out to obtain the aerodynamic heating data of the model surface under both near complete catalysis and near non-catalysis. Based on the comparative analysis of test results and numerical calculation results, the numerical prediction method of high temperature chemical non-equilibrium aerodynamic heating is validated. The results show that the catalytic properties of the surface material have a significant effect on the non-equilibrium aerodynamic heating; the catalytic effect on the spherical surface is obvious, the complete catalytic heating is higher than the non-catalytic heating, but the catalytic effect on the cylinder surface is weaker. The numerical simulation results show that the difference of the heat flux between the different wall catalytic conditions is greater than that of the ground test results; completely catalytic wall heat flux within 5% of the difference, completely non-catalytic wall heat flux difference of more than 10%.

THE AERODYNAMIC CHRACTERISTICS CALCULATION METHODOLOGY OF TWO-SHELL PARAGLIDERS

Currently, two-shell paragliders (TSP) find a sufficiently wide application, including the solution of transport problems. A two-shell paraglider is a soft wing, the form of which is supported by the high-speed pressure in the stream and it is a complex aeroelastic system. To determine the aerodynamic characteristics of such system the use of nonlinear aerodynamics and nonlinear theory of elasticity methods is required, it causes the significant computational difficulties. This paper studies the aerodynamic characteristics of various steady-state shapes of gliding parachutes, the calculation-experimental method of their calculation is proposed. It is shown that the replacement of the volumetric profile of TSP median surface allows to receive the results which correctly reflect the qualitative effects of stalled and attached flows. It leads to the assumption that such replacement was possible for obtaining data about the main patterns of parachute finite wings span flow. The aerodynamic characteristics data of TSP steady-state shapes allow to identify the regularities of their changes depending on parachute cutting shape, the deformations of its surface caused by the incoming flow or control actions. To solve the problem of gliding parachute stall, with a stream of air, the discrete vortex method with closed frameworks is used. This method allows to calculate the aerodynamic characteristics of parachutes. The middle surface airflow of TSP steady-state shape with the flow of an ideal incompressible fluid is examined. The parachute fabric permeability is not considered because the upper and lower TSP cloth is either made of low permeable or impermeable fabric. The stalled aerodynamic coefficients are determined by time averaging after calculations up to its larger values. The results of the calculations are given. The possibility of application the proposed methodology for calculation of TSP aerodynamic characteristics in the range of angles of attack to 10° and over 20° for the simplified calculation scheme with accuracy 10% is shown. At the same time, it is revealed that with the increase of soft wing elongation, it is important to consider its main surface curvature for more precise aerodynamic characteristics definition. The proposed methodology can be used for rapid assessments of aerodynamic forces at the design stage and in planning tube experiment. The obtained results can be useful in TSP design during the performance of the tube experiments.

Design of mistuning patterns to control the vibration amplitude of unstable rotor blades

Flutter onset is one of the major causes for increased vibration levels in low pressure turbine (LPT) rotor blades. This paper describes the design process and the experimental testing of intentional mistuning patterns specifically chosen to show the possibility to control the flutter characteristics of an LPT rotor. The Asymptotic Mistuning Model (AMM) methodology is used to select the intentional mistuning patterns. The AMM formulation incorporates elastic and aerodynamic data from detailed FEM and CFD computations, and measured values of the rotor blades intrinsic mistuning. The intentional mistuning patterns are implemented in the rotor by mounting small masses at the tip-shroud of the blades, and the effect of these small masses is also introduced in the AMM description. Two intentional mistuning patterns are selected. The classical alternate mistuning pattern, designed to fully suppress flutter, and a second intentional mistuning pattern that is designed with the idea of halving the vibration amplitude of the tuned unstable rotor. This second mistuning pattern demonstrates that, through the implementation of the appropriate intentional mistuning pattern, flutter cannot only be suppressed but also modulated. The two mistuned LPT rotors were tested in a free flutter experiment at a high speed rotating wind-tunnel, and the experimental results showed a good agreement with the AMM stability predictions. This is the first time, to our knowledge, that the possibility to control flutter through intentional mistuning has been experimentally validated in a rotating rig. The AMM is also applied to evaluate the effect of the aerodynamic coupling in the stability calculations of the mistuned rotors, and the AMM results are compared with high fidelity numerical calculations. It is shown that, despite its very reduced formulation, the AMM produces quite accurate stability predictions, and that it is essential to take into account the aerodynamic coupling; if it is not considered then the instability level of the mistuned rotors can be substantially underestimated.

Retrospective on the Common Research Model for Computational Fluid Dynamics Validation Studies

The development of a wing–body–nacelle–pylon–horizontal-tail configuration for a common research model is presented, with the focus on the aerodynamic design of the wing. A contemporary transonic supercritical wing design is developed with aerodynamic characteristics that are well behaved and of high performance for configurations with and without the nacelle–pylon group. The horizontal tail is robustly designed for dive Mach number conditions and is suitably sized for typical stability and control requirements. The fuselage is representative of a wide-body commercial transport aircraft; it includes a wing–body fairing, as well as a scrubbing seal for the horizontal tail. The nacelle is a single-cowl high-bypass-ratio flowthrough design with an exit area sized to achieve a natural unforced mass flow ratio typical of commercial aircraft engines at cruise. The simplicity of this un-bifurcated unpowered nacelle geometry facilitates experimental data collection and grid generation efforts for computational fluid dynamics (CFD) validations. Detailed aerodynamic performance data are provided; however, this information was originally presented in such a manner as to not bias CFD predictions planned for the fourth AIAA CFD Drag Prediction Workshop in 2009 (DPW-IV); the DPW-IV incorporated this common research model into its blind test cases. The fifth AIAA CFD Drag Prediction Workshop in 2012 and the sixth AIAA CFD Drag Prediction Workshop in 2016 also used this configuration as the basis of their test cases. The CFD results presented include wing pressure distributions with and without the nacelle–pylon Mach lift-to-drag ratio (ML/D) trend lines, as well as the drag-divergence curves. The design point for the wing–body configuration is within 1% of its maximum ML/D. The original plans to test the common research model in the National Transonic Facility at NASA Langley Research Center and the 11-by-11 ft wind tunnel at NASA Ames Research Center are discussed. Furthermore, wind-tunnel models have been replicated by the Japan Aerospace Exploration Agency, ONERA–The French Aerospace Lab, the University of Washington, as well as by numerous other laboratories. A Web site has been established to collect, archive, and freely provide wind-tunnel data from these various experimental campaigns. The geometry definition has been extended to include a high-lift system. It has been used to form the basis for experimental swept-wing icing studies. Finite element models have been developed for the wind-tunnel environment, as well as to be more representative of a full-scale aircraft in flight. A simple search for technical papers related to this configuration yields thousands of results. Needless to say, with a decade in retrospect, the NASA Common Research Model has significantly exceeded the initial most-optimistic goals, and it has become the de facto standard test case for present-day transonic CFD validations.

Source characteristics of voiceless dorsal fricatives

Aerodynamic and acoustic data on voiceless dorsal fricatives [x/χ] in Arabic, Persian, and Spanish were recorded to measure the extent to which such productions involve trilling of the uvula, thus exhibiting a sound source which, contrary to assumptions for voiceless fricatives, is mixed rather than aperiodic. Oscillation in airflow indicative of uvular vibration was present more often than not in Arabic (63%) and Persian (75%), while Spanish dorsal fricatives were more commonly produced with unimodal flow indicative of an aperiodic source. When present, uvular vibration frequencies averaged 68 Hz in Arabic and 67 Hz in Persian. Rates of uvular vibration were highly variable, however, and ranged between 40 and 116 Hz, with oscillatory periods averaging 4-5 cycles in duration, with a range of 1-12. The effect of these source characteristics on dorsal fricative acoustics was to significantly skew the spectral shape parameters (M1-M4) commonly used to characterize properties of the anterior filter; however, spectral peak frequency was found to be stable to changes in source characteristics, suggesting the occurrence of trilled tokens is not due to velar-uvular allophony, but rather is more fundamental to dorsal fricative production.

Implementación de sistema para la medición de fuerzas aerodinámicas en un túnel de viento subsónico

El Centro de Estudios Aeronáuticos (CEA) de la Aeronáutica Civil (UAEAC) ubicado en la ciudad de Bogotá, Colombia, cuenta con un túnel de viento subsónico denominado ELD 402B tipo Eiffel para el desarrollo de prácticas de aerodinámica. Esto le permite al Grupo de Investigación Aeronáutica (G.IN.A) de la institución contar con una herramienta para realizar labores en investigación y docencia. Por lo cual se propone como objetivo desarrollar un sistema de adquisición de datos aerodinámicos y la interfaz del usuario del túnel de viento subsónico. Con el fin de ampliar las capacidades de este túnel de viento, se desarrolló e implementó un sistema que permite adquirir las señales de los sensores de la balanza aerodinámica, ubicados en la sección de pruebas del túnel de viento. La adquisición y procesamiento se realizó con la herramienta de software LabVIEW, con la cual se implementó una interfaz gráfica que permite visualizar las variables entregadas por los sensores, las fuerzas aerodinámicas principales en el perfil alar de prueba, coeficientes aerodinámicos y velocidad relativa del flujo de aire al momento del experimento. En este documento se presentan los resultados de las pruebas de funcionamiento y el proceso de diseño e implementación del sistema que permite hacer mediciones de las variables aerodinámicas, como son los coeficientes de sustentación y arrastre para el modelo que se encuentre en la sección de pruebas del túnel de viento en tiempo real.

Characterisation of football trajectories for assessing flight performance

Much discussion surrounds the flight of association footballs (soccer balls), particularly where the flight may be perceived as irregular. This is particularly prevalent in high-profile competitions due to increased camera coverage and public scrutiny. All footballs do not perform in an identical manner in flight. This article develops methods to characterise the important features of flight, enabling direct, quantitative comparisons between ball designs. The system used to generate the flight paths included collection of aerodynamic force coefficient data in a wind tunnel, which were input into a flight model across a wide range of realistic conditions. Parameters were derived from these trajectories to characterise the in-flight deviations across the range of flights from which the aerodynamic performance of different balls were statistically compared. The amount of lateral movement in flight was determined by calculating the final lateral deviation from the initial shot vector. To quantify the overall shape of the flight, increasing orders of polynomial functions were fitted to the flight path until a good fit was obtained with a high-order polynomial indicating a less consistent flight. The number of inflection points in each flight was also recorded to further define the flight path. The orientation dependency of a ball was assessed by comparing the true shot to a second flight path without considering orientation-dependent forces. The difference between these flights isolated the effect of orientation-dependent aerodynamic forces. The article provides the means of quantitatively describing a ball’s aerodynamic behaviour in a defined and robust mathematical process. Conclusions were not drawn regarding which balls are good and bad; these are subjective terms and can only be analysed through comprehensive player perception studies.