Academic literature on the topic 'Global aerodynamic coefficients'

The performance of vehicle dynamic model (VDM)-based navigation largely depends on the accurate determination of aerodynamic coefficients that are unknown a priori. Among different techniques, such as model simulations or experimental analysis in a wind tunnel, the method of self-calibration via state-space augmentation benefiting Global Navigation Satellite System (GNSS) positioning represents an interesting and economical alternative. We study this technique under simulation with the goal of determining the impact of aircraft maneuvers on the precision and (de)-correlation of the aerodynamic coefficients among themselves and with respect to other error-states. A combination of different maneuvers indicates to be essential for obtaining satisfactory aerodynamic coefficients estimation and reduce their uncertainty.

Although much employed, wind energy systems still present an open, contemporary topic of many research studies. Special attention is given to precise aerodynamic modeling performed in the beginning since overall wind turbine performances directly depend on blade aerodynamic performances. Several models different in complexity and computational requirements are still widely used. Most common numerical approaches include: i) momentum balance models, ii) potential flow methods and iii) full computational fluid dynamics solutions. Short explanations, reviews and comparison of the existing computational concepts are presented in the paper. Simpler models are described and implemented while numerous numerical investigations of isolated horizontal-axis wind turbine rotor consisting of three blades have also been performed in ANSYS FLUENT 16.2. Flow field is modeled by Reynolds Averaged Navier-Stokes (RANS) equations closed by two different turbulence models. Results including global parameters such as thrust and power coefficients as well as local distributions along the blade obtained by different models are compared to available experimental data. Presented results include fluid flow visualizations in the form of velocity contours, sectional pressure distributions and values of power and thrust force coefficients for a range of operational regimes. Although obtained numerical results vary in accuracy, all presented numerical settings seem to slightly under- or over-estimate the global wind turbine parameters (power and thrust force coefficients). Turbulence can greatly affect the wind turbine aerodynamics and should be modeled with care.

The analysis of the aerodynamic force coefficients of the Holy Trinity Column in Olomouc based on the experimental wind tunnel testing is presented. Two aerodynamic models corresponding to geometrical scales 1:75 and 1:150 were built using 3D-printer and tested in the smooth flow in order to define the global static wind effects. The larger model served as a reference case for the tests of the isolated column, while the model build with smaller scale enabled also the experimental examination of the influence of the closest surroundings. The comparison of the aerodynamic coefficients obtained from the testing of both models for various wind speeds confirms their similarity and interchangeability. The independence of the coefficients on Reynolds number, Re, were successfully verified and the presented coefficients were determined for Re = 2.7 105 for a large number of angles of wind attack. The significant decrease in the static wind load due to the surrounding buildings were observed. The obtained results can broaden the knowledge of wind load related to this type historical monuments and can be useful when deciding about their global maintenance, a type of remedial work or their conservation.

Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the AVT-183 diamond wing configuration with variation of leading-edge roughness size and Reynolds number. Wind tunnel testing applying force and surface pressure measurements are conducted and the results presented and analysed. For the investigated Reynolds number range of 2.1 × 10 6 ≤ R e ≤ 2.7 × 10 6 there is no significant influence on the aerodynamic coefficients. However, leading-edge roughness height influences the vortex separation location. Trip dots produced the most downstream located vortex separation onset. Increasing the roughness size shifts the separation onset upstream. Prior to stall, global aerodynamic coefficients are little influenced by leading-edge roughness. In contrast, maximum lift and maximum angle of attack is reduced with increasing disturbance height. Surface pressure fluctuations show dominant broadband frequency peaks, distinctive for moderate sweep vortex breakdown. The experimental work presented here provides insights into the aerodynamic characteristics of diamond wings in a wide parameter space including a relevant angle of attack range up to post-stall.

Utilizing the interference of shock and expansion waves, supersonic biplane can reduce the wave drag remarkably. However, the supersonic biplane is only designed at special conditions, so that it has poor performance at off-design conditions. To analyze supersonic biplane's aerodynamic characteristics at off-design conditions, the non-instructive probabilistic collocation method has been employed to achieve uncertainty quantification. Besides, Sobol global sensitivity is adopted to accurately evaluate the influence of the input uncertainty parameters. The uncertainty parameters are Mach number and the angle of attack which both satisfy special normal distributions. Aerodynamic coefficients and pressure distribution from the biplane's surface as well as flow filed are studied. The results of uncertainty quantification show that the main reason for aerodynamic characteristics fluctuations is the pressure pulsation from the maximum thickness of the lower airfoil's upper surface. The results of global sensitivity show that Mach number is the most important factor for the variation of aerodynamic performance.

Nowadays, aerodynamics is a key focal point in the vehicle design process. Beyond its direct impact on the performance of a vehicle, it also has significant effects on economics and safety. In the last decade numerical methods, mainly Computational Fluid Dynamics (CFD), have established themselves as a reliable tool that assists in the design process and complements classical tunnel tests. However, questions remain about the possible obtained accuracy, best practices and applied turbulence models. In this paper, we present a comprehensive study of motorcycle aerodynamics using CFD methods which, compared to the most common car aerodynamics analysis, has many specific features. The motorcycle, along with its rider, constitutes a shape with very complex aerodynamic properties. A detailed insight into the flow features is presented with detailed commentary. The front fairing, the front wheel and its suspension were identified as the main contributors to the aerodynamic drag of the motorcycle and its rider. The influence of rider position was also studied and identified as one of the most important elements when considering motorcycle aerodynamics. An extensive turbulence models study was performed to evaluate the accuracy of the most common Reynolds-averaged Navier–Stokes models and novel hybrid models, such as the Scale Adaptive Simulation and the Delayed Detached Eddy Simulation. Similar values of drag coefficients were obtained for different turbulence models with noticeable differences found for k−ϵ models. It was also observed that near-wall treatment affects the flow behaviour near the wheels and windshield but has no impact on the global aerodynamic parameters. In the summary, a discussion about the obtained results was set forth and a number of questions related to specifics of motorcycle CFD simulations were addressed.

Abstract The paper presents a numerical analysis of the impact of working propellers on the aerodynamics of the aircraft. Analysis was made on the example of a twin-engined, unmanned aircraft with electric drive during the low altitude flight. Three configurations were studied and compared: the plane without propellers, the plane with pusher propellers and the plane with tractor propellers. For each configuration distributions of aerodynamic coefficients along the span of the wing and their global values for the entire aircraft were estimated. Calculations were performed using the Fluent solver with implementation of a simplified model of propeller based on the Blade Element Theory. Results of the analysis indicate a slight advantage of the tractor propellers configuration.

In this work, a new approach for aerodynamic optimization of horizontal axis wind turbine (HAWT) airfoil is presented. This technique combines commercial computational fluid dynamics (CFD) codes with differential evolution (DE), a reliable gradient-free global optimization method. During the optimization process, commercial CFD codes are used to evaluate aerodynamic characteristics of HAWT airfoil and an improved DE algorithm is utilized to find the optimal airfoil design. The objective of this research is to maximize the aerodynamic coefficients of HAWT airfoil at the design angle of attack (AOA) with specific ambient environment. The airfoil shape is modeled by control points which their coordinates are design variables. The reliability of CFD codes is validated by comparing the analytical results of a typical HAWT airfoil with its experimental data. Finally, the optimal design of wind turbine airfoil is evaluated about aerodynamic performance in comparison with existing airfoils and some discussions are performed.

Abstract. Floating offshore wind turbines are subjected to large motions due to the additional degrees of freedom of the floating foundation. The turbine rotor often operates in highly dynamic inflow conditions, and this has a significant effect on the overall aerodynamic response and turbine wake. Experiments are needed to get a deeper understanding of unsteady aerodynamics and hence leverage this knowledge to develop better models and to produce data for the validation and calibration of existing numerical tools. In this context, this paper presents a wind tunnel experiment about the unsteady aerodynamics of a floating turbine subjected to surge motion. The experiment results cover blade forces, rotor-integral forces, and wake. The 2D sectional model tests were carried out to characterize the aerodynamic coefficients of a low-Reynolds-number airfoil with harmonic variation in the angle of attack. The lift coefficient shows a hysteresis cycle close to stall, which grows in strength and extends in the linear region for motion frequencies higher than those typical of surge motion. Knowledge about the airfoil aerodynamic response was utilized to define the wind and surge motion conditions of the full-turbine experiment. The global aerodynamic turbine response is evaluated from rotor-thrust force measurements, because thrust influences the along-wind response of the floating turbine. It is found that experimental data follow predictions of quasi-steady theory for reduced frequency up to 0.5 reasonably well. For higher surge motion frequencies, unsteady effects may be present. The turbine near wake was investigated by means of hot-wire measurements. The wake energy is increased at the surge frequency, and the increment is proportional to the maximum surge velocity. A spatial analysis shows the wake energy increment corresponds with the blade tip. Particle image velocimetry (PIV) was utilized to visualize the blade-tip vortex, and it is observed that the vortex travel speed is modified in the presence of surge motion.

La thèse s'intéresse à une problématique concrète de sécurité des aéronefs. Le domaine de vol post-décroché est un domaine aérodynamiquement complexe où l'écoulement autour des surfaces portantes (ailes et gouvernes) peut présenter de fortes instabilités et peut être partiellement ou massivement décollé. Dans ce domaine de vol, atteignable de façon accidentelle ou volontaire (avions d'entraînement ou de voltige), les moyens de contrôle usuels sont moins efficaces, voire totalement inefficaces, ce qui peut mettre en danger le pilote et ses potentiels passagers. Le travail de recherche s'intéresse à la détermination des prévisions de vol dans le domaine de vol post-décroché, ainsi qu'à leurs dépendances aux structures de modèles utilisées pour les coefficients aérodynamiques et aux incertitudes des données expérimentales sur lesquelles ce modèle repose. La dynamique du mouvement de l'avion est régie par un système dynamique d'équations différentielles ordinaires autonomes non linéaires. Dans ces équations, les effets du fluide sur l'aéronef apparaissent par le biais des coefficients aérodynamiques globaux, qui sont les forces et les moments adimensionnés appliqués par le fluide sur l'aéronef. Ces coefficients dépendent de façon non-linéaire d'un grand nombre de variables, dont la géométrie de l'aéronef, sa vitesse et sa vitesse de rotation par rapport à la Terre, ainsi que des caractéristiques de l'écoulement qui l'entoure. Pour chaque coefficient, un modèle de représentation ayant une certaine structure est déterminé pour décrire ces dépendances complexes. Ce modèle s'appuie sur des données expérimentales recueillies sur des maquettes de taille réduite, les données de vol libre sur avion réel étant trop coûteuses et trop risquées à collecter dans le domaine post-décroché. Une autre piste pour l'établissement de ces bases serait d'utiliser des données venant de calculs numériques. Néanmoins, le caractère instationnaire et complexe de l'écoulement autour de la géométrie 3D de l'aéronef semble rendre les simulations trop coûteuses en terme de temps de calcul pour le moment, même si des études récentes explorent cette direction de recherche. Les modèles utilisés dans le cadre de notre étude sont bâtis exclusivement sur des données expérimentales. Dans le système dynamique, les coefficients aérodynamiques globaux sont évalués par interpolation dans ces tables de données d'après la structure du modèle choisie. De par la nécessité de sélectionner une structure simplificatrice du modèle de représentation des coefficients aérodynamiques globaux, ces modèles sont lacunaires. De plus, ils sont entachés d'incertitudes dues au caractère intrinsèque des expériences. Ces lacunes et ces incertitudes vont impacter les résultats des prévisions de vol. L'objectif initial de la thèse est d'étudier ces impacts.Lors des travaux de thèse, de nouveaux objectifs scientifiques ont émergé. En premier lieu, une nouvelle méthode multi-éléments basée sur des méthodes modernes d'apprentissage automatique est développée. Les méthodes multi-éléments sont des méthodes qui ont été développées pour pallier au manque de précision des polynômes du chaos en présence de discontinuités. En second lieu, une formule analytique reliant les indices de sensibilité de Sobol aux coefficients d'un métamodèle multi-éléments est démontrée. Ces méthodes sont ainsi utilisées dans le cas de la dynamique du vol pour répondre à l'objectif initial de la thèse. Les nombreuses bifurcations que possède le système dynamique du vol peuvent se traduire par des irrégularités et/ou des discontinuités dans l'évolution des variables d'état par rapport aux paramètres incertains. Les méthodes d'analyse de sensibilité et de quantification d'incertitude développées sont alors de bonnes candidates pour effectuer l'analyse du système
The thesis is addressing a concrete issue on aircrafts safety. The post-stall flight domain is a complex flight domain where flows around an airfoil may be highly unstable and massively stalled. In this domain, which can be reached on purpose or accidentally, usual controls are less efficient or completely inefficient, which can endanger the pilot and its passengers. The thesis is about the determination of the flight predictions in the post-stall flight domain, their dependences to the selected model structure and about the uncertainties of the experimental data the model relies on. The dynamic of the motion of the aircraft is governed by a dynamic system of ordinary non-linear differential equations. In these equations, the effects from the fluid on the aircraft are traduced by the global aerodynamic coefficients, the dimensionless forces and moments applied by the fluid on the aircraft. These coefficients depend on a high number of variables in a non-linear fashion. Among these variables are the geometry of the aircraft, its velocity and its rotation rates compared to earth, and characteristics of the surrounding flow. A representation model having a selected structure is determined for every aerodynamic coefficient, in order to represent these complex dependences. This model rely on experimental data obtained on a scale model, free flight data on a real aircraft being too expensive and too risky to get in the post-stall domain. Another way of obtaining data would be to use computational simulations. Nevertheless, the complex and unsteady flows around the 3D geometry of the aircraft makes the simulation too expensive with the current ressources, even if some recent studies begin to explore this direction of research. The selected models in the thesis are built on experimental data only. In the dynamic system, the global aerodynamic coefficients are evaluated by interpolation in these databases according to the selected model structure. The fact of selecting a simplified structure of the model makes it deficient. Moreover, as these models rely on experimental data, they are uncertain. The gaps and the uncertainties of the model have some impacts on the flight predictions. The initial objective of the thesis is therefore to study these impacts.During the thesis, new scientific objectives appeared, objectives going beyond the scope of Flight Dynamics. First, a new multi-element surrogate model for Uncertainty Quantification based on modern Machine learning methods is developed. Multi-element surrogate models were developed to address the loss of accuracy of Polynomial Chaos model in presence of discontinuities. Then, a formula linking the sensitivity Sobol indices to the coefficient of a multi-element surrogate model is derived. These results are used in the case of Flight Dynamics in order to address the issue raised in the initial objective of the thesis. The numerous bifurcations of the dynamic system can be traduced by discontinuities and/or irregularities in the evolution of the state variables compared to the uncertain parameters. The methods of Sensitivity Analysis and of Uncertainty Quantification developed in the thesis are therefore good candidates to analyse the system

AbstractConcerns over global warming and the need to reduce carbon emissions have prompted the development of novel energy recovery systems. During urban driving, a significant amount of energy is lost due to continuous braking, which can be recovered and stored. The flywheel energy storage system can efficiently recover and store the vehicle's kinetic energy during deceleration. In this study, a Computational Fluid Dynamics (CFD) model was developed to assess the impact of air gap size, and rotor cavity pressure environment on the aerodynamic performance of an enclosed non-ventilated flywheel energy recovery system. Consequently, the flywheel rotor skin friction coefficients for various air gap sizes have been numerically determined to predict the windage losses over a wide operating range. The presented study aims to identify a correlation that accurately fits the rotor skin friction coefficients for a range of air gap sizes and operating conditions. Model validation was carried out to assess the validity of the CFD results, which showed good agreement between numerical and experimental data. The results demonstrated that the increase in the air gap size can lead to up to a 19% reduction in the windage loss depending on the operating speed of the flywheel, while the windage loss can be reduced by 33% when the operating pressure is reduced to 500 mbar. Windage losses can be reduced by 45% when the airgap size is greatest, and the operating pressure is lowest.

This research aims to examine the flow field over a NACA 651-412 aerofoil at a supersonic Mach number (M = 2) in the presence of a sharp spike and a Hemi spherical head spike. Using a spike integrated with an aerofoil alters the flow characteristics of the aerofoil, resulting in changes in aerodynamic lift and drag. Flow visualisation graphs and coefficients of aerodynamic drag and lift are measured. In this work, two spike designs were employed: sharp edges and hemispherical edges. The flow over an aerofoil with and without a spike is also compared in order to comprehend the performance of the NACA 6 series aerofoil with different geometry alteration. For computational simulation, ICEM CFD is used as a meshing tool and ANSYS fluent as an adjoint solver to analyse the external flow over the body. Furthermore, the drag increases significantly when the flight angle of attack increases. Employing certain installation angles effectively improves the drag reduction around the angle of attack and improve the lift-to-drag ratio.

In order to separately describe the dominating loss mechanisms in pre-swirled cooling air delivery systems, discharge, temperature and velocity measurements were performed for numerous designs. Whereas pre-swirl nozzles, as first component, were characterized by their discharge coefficients, total pressure losses occurring at the inlet of the receiver holes were correlated depending on the incident angle of the cooling flow. To quantify losses generated inside the rotor-stator gap, flow velocity data, acquired by means of 3D PIV, were compared to total temperature measurements. In addition the influence of wall friction and mixing losses due to the strong velocity gradients inside the preswirl chamber was discussed by means of a simple loss model. Finally, dimensionless loss coefficients, discharge behaviour and expected cooling temperature can be predicted for a family of realistic pre-swirl systems. Moreover, this detailed description of the losses provides a methodology to quantify the impact of individual loss sources on the global efficiency of the pre-swirl system, thus allowing improved designs.

This paper proposes a formulation for the assessment of the unsteady aerodynamics of floating offshore wind turbines, based on wind tunnel experiments through surge and pitch imposed motions on the 1/75 DTU 10 MW scale model. Rotor thrust and torque were analysed out of a set of different combinations of amplitudes and frequencies of the imposed mono-harmonic motion, following the idea of splitting these forces into steady and unsteady contributions, respectively through steady and unsteady aerodynamic coefficients. The latter were analysed, for different tip-speed ratios, both experimentally and numerically, with respect to a newly introduced parameter, the “wake reduced velocity”, which turned out to be effective in the description of the unsteady regime. Experimental results have shown good consistency of the formulation and put the basis for further studies on this topic, for the comprehension of this phenomenon and for the development of reduced-order models for control purposes, with the focus of the global system dynamics.

Low-speed model testing has advantages such as great accuracy, low cost and risk, so it’s widely used in the design procedure of HPC exit stage. The low-speed model testing project is conducted in Nanjing University of Aeronautics and Astronautics, to represent aerodynamic load and flow field structure of the seventh stage of a high-performance 10-stage high-pressure compressor. This paper outlines the design work of the low speed four-repeating-stage axial compressor, the third stage of which is the testing stage. The first two stages and the last stage provide the compressor with entrance and exit conditions respectively. The high-to-low speed transformation process involves both geometric and aerodynamic considerations. Accurate similarities demand the same Mach number and Reynolds number, which will not be maintained due to motor power/size and its low-speed feature. Compromises of constraints are obvious. Modeling principles are presented in high-to-low speed transformation. Design work is carried out based on these principles. Four main procedures are proceeded subsequently in the general design, including establishment of low-speed modeling target, global parameter design of modeling stage, throughflow aerodynamic design and blading design. In global parameter design procedure, rotational speed, shroud diameter, hub-tip ratio, mid-span chord and axial spacing between stages are determined by geometrical modeling principles. During throughflow design process, radial distributions of aerodynamic parameters such as D-Factor, pressure-rise coefficient, loss coefficients, stage reaction and other parameters are obtained by determined aerodynamic modeling principles. Finally, rotor and stator blade profiles of LSRC at seven span locations are adjusted, to make sure that blade surface pressure coefficients agree well with that of the HPC. 3D flow calculations are performed on low-speed four-stage axial compressor, and the resultant flow field structures agree well with that of the HPC. It’s worth noting that a large separation zone appears in both suction surfaces of LSRC and HPC. How to diminish it through 3D blading design in LSRC test rig is our further work.

A brush-labyrinth sealing configuration consisting of two labyrinth fins upstream and one brush seal downstream is studied experimentally and theoretically. Two slightly different brush seal designs with zero cold radial clearance are considered. The sealing configurations are tested on the no-whirl and dynamic test rigs to obtain leakage performance and rotordynamic stiffness and damping coefficients. The no-whirl tests allow identification of the local rotordynamic direct and cross-coupled stiffness coefficients for a wide range of operating conditions, while the dynamic test rig is used to obtain both global stiffness and damping coefficients, but for a narrower operating range limited by the capabilities of a magnetic actuator. Modeling of the brush-labyrinth seals is performed using computational fluid dynamics. The experimental global rotordynamic coefficients consist of an aerodynamic component due to the gas flow and a mechanical component due to the contact between the bristle tips and rotor surface. The CFD-based calculations of rotordynamic coefficients provide however only the aerodynamic component. A simple mechanical model is used to estimate the theoretical value of the mechanical stiffness of the bristle pack during the contact. The results obtained for the sealing configurations with zero cold radial clearance brush seals are compared with available data on three-tooth-on-stator labyrinth seals and a brush seal with positive cold radial clearance. Results show that the sealing arrangement with a line-on-line welded brush seal has the best performance overall with the lowest leakage and cross-coupled stiffness. The predictions are generally in agreement with the measurements for leakage and stiffness coefficients. The seal damping capability is noticeably underpredicted.

A prerequisite for aeroelastic stability investigations on vibrating compressor cascades is the detailed knowledge of the unsteady aerodynamic loads acting on the blades. In order to obtain precise insight into the aerodynamic damping of a vibrating blade assembly, a basic experiment was performed where unsteady pressure distributions were measured for subsonic and transonic flow conditions. The experiments were performed on a non-rotating, two-dimensional section of a compressor cascade in an annular test facility. The cascade consists of 20 blades (NACA3506 profile) mounted on elastic spring suspensions. In order to measure the unsteady pressure distribution, the cascade was set to tuned pitching oscillations (traveling wave modes). Each blade was driven to controlled harmonic torsional motions around midchord by a magnetic excitation system and by inductive displacement probes which measure the feedback signal of the motion. Steady and unsteady pressures were measured by steady pressure taps and piezo-electric pressure transducers, respectively. The measurement of the unsteady aerodynamic response to a shock vibrating on the suction side of the blades was enabled by a dense spacing of transducers in this region. The global aerodynamic stability is assessed by a damping coefficient evaluated from the out-of-phase parts of the unsteady moment coefficients and by the contributions from the local work coefficient, using the measured pressure data.

The big data and machine learning are developing rapidly, and their applications in the aerodynamic design of centrifugal impellers and other turbomachinery have attracted wide attention. In this paper, centrifugal impellers with large flow coefficient (0.18-0.22) are taken as research objects. Firstly, through one-dimensional design and optimization, main one-dimensional geometric parameters of those centrifugal impellers are obtained. Subsequently, hundreds of samples of centrifugal impellers are obtained by using an in-house parameterization program and Latin hypercube sampling method. The NUMECA software is used for CFD calculations to build a sample library of centrifugal impellers. Then, applying the artificial neural network (ANN) to deal with the he data in the sample library, a nonlinear model between the flow coefficients, the geometric parameters of these centrifugal impellers and the aerodynamic performance is constructed, which can replace the CFD calculation. Lastly with the help of the multi-objective genetic algorithm, a global optimization is carried out to fulfull a rapid design optimization for centrifugal impellers with flow coefficients in the range of 0.18- 0.22. Three examples provided in the paper show that the design and optimization method described above is faster and more reliable compared with the traditional design method. This method provides a new way for the rapid design of centrifugal impellers.

In this paper, a novel global optimization algorithm has been developed, which is named as Particle Swarm Optimization combined with Particle Generator (PSO-PG). In PSO-PG, a particle generator was introduced to iteratively generate the initial particles for PSO. Based on a series of comparable numerical experiments, it was convinced that the calculation accuracy of the new algorithm as well as its optimization efficiency was greatly improved in comparison with those of the standard PSO. It was also observed that the optimization results obtained from PSO-PG were almost independent of some critical coefficients employed in the algorithm. Additionally, the novel optimization algorithm was adopted in the airfoil optimization. A special fitness function was designed and its elements were carefully selected for the low-velocity airfoil. To testify the accuracy of the optimization method, the comparative experiments were also carried out to illustrate the difference of the aerodynamic performance between the optimized and its initial airfoil.

Abstract Global climate change has affected the human race for decades. As a result, severe weather changes and more substantial hurricane impact have become a typical scenario. Utility trucks with the morphing boom equipment are the first responders to access these disaster areas in bad weather conditions and restore the damages caused by the disaster. The stability of the utility trucks while driving in a heavy wind scenario is an essential aspect for the safety of the rescue crew, and aerodynamic forces caused by the wind flow constitute a significant factor that influences the stability of the utility truck. In this paper, the aerodynamic performance of the utility truck is modeled using the incompressible unsteady Reynolds Averaged Navier Stokes (URANS) model. The Ahmed body, a well-recognized benchmark test case used by the computational fluid dynamics (CFD) community for the aerodynamic model validation of automobiles, is used to validate this aerodynamic model. The validated aerodynamic model investigates the impact of heavy wind on the utility truck with the morphing boom equipment. The visualization of the flow field around the utility truck with the force and moment coefficients at various side slip angles are presented in this paper.

In this paper, a systematic CFD work is carried out with the aim to inspect the influence of different cascade parameters on the aerodynamic performance of a reversible fan blade profile. From the obtained results, we derive a meta-model for the aerodynamic properties of this profile. Through RANS simulations of different arrangements in cascades, the aerodynamic performance of airfoils are analyzed as Reynolds number, solidity, pitch angle and angle of attack are varied. The definition of a trial matrix allows the reduction of the minimum number of simulations required. The computed CFD values of lift and drag coefficients, stall margin and the zero-lift angle strongly depend on cascade configuration and differ significantly from standard panel method software predictions. In this work, X-Foil has been used as a benchmark. Particularly, the high influence of pitch angle and solidity is here highlighted, while a less marked dependence from the Reynolds number has been found. Meta-models for lift and drag coefficients have been later derived, and an analysis of variance has improved the models by reducing the number of significant factors. The application of the meta-models to a quasi-3D in-house software for fan performance prediction is also shown. The effectiveness of the derived meta-models is proven through a spanwise comparison of a reversible fan with the X-Foil based and meta-model based versions of the software and 3D fields from a standard CFD simulation. The meta-model improves the software prediction capability, leading to a very low global overestimation of the specific work of the fan.

In modern low pressure turbines the efforts to increase aerodynamic blade loading by increasing blade pitch and optimising midspan performance in order to reduce weight and complexity can produce increased losses in the endwall region. Airfoils of high flow turning and high pressure gradients between the blades generate strong secondary flows which impair the global aerodynamic performance of the blades. In addition, the unsteady incoming wakes take influence on transition phenomena on the blade surfaces and the inlet boundary layer, and consequently affect the development and the evolution of the secondary flows. In this paper the T106 cascade is used to identify the effect of unsteady wakes on the development of secondary flows in a turbine cascade. Numerical and experimental results are compared at different flux coefficients and Strouhal numbers, the relative differences and similarities are analysed.