Aerodynamics

This work is focused on the aerodynamic analysis of a small satellite provided with a deployable aerobrake. The satellite is intended to perform a completely aerodynamic de-orbiting maneuver from Low-Earth-Orbit. A brief discussion about the aerodynamic effects of the position of the aero-brake along the longitudinal axis of a simplified axisymmetric system is presented. Moreover, a more complex architecture, envisaging deployable solar panels for the enhancement of power generation along the orbital path, is proposed and analyzed. The present paper is aimed at the evaluation of the influence of such a configuration on the satellite aerodynamic parameters. Computations have been carried out by means of a Direct Simulation Monte Carlo (DSMC) code at altitude of 150 km, velocity of 7800 m/s and in the interval of angle of attack 0-180 deg with a spacing of 10 deg. The results verified that the deployable solar panels strongly influence Aerodynamics of the satellite. One of the most relevant aspects is the variation of the longitudinal stability equilibrium that becomes more stable. Furthermore, the deployable solar panels increase the aerodynamic drag when the aero-brake is closed, affecting the drag modulation capability.

HyPlane is the Italian aerospaceplane proposal targeting, at the same time, both the space tourism and point-to-point intercontinental hypersonic flights. Unlike other aerospaceplane projects, relying on boosters or mother airplanes that bring the vehicle to high altitude, HyPlane will take off and land horizontally from common runways. According to the current project, HyPlane will fly sub-orbital trajectories under high-supersonic/low-hypersonic continuum flow regimes. It can go beyond the von Karman line at 100 km altitude for a short time, then starting the descending leg of the trajectory. Its aerodynamic behavior up to 70 km have already been studied and the results published in previous works. In the present paper some aspects of the aerodynamic behavior of HyPlane have been analyzed at 80, 90 and 100 km. Computer tests, calculating the aerodynamic parameters, have been carried out by a Direct Simulation Monte Carlo code. The effects of the Knudsen, Mach and Reynolds numbers have been evaluated in clean configuration. The effects of the aerodynamic surfaces on the rolling, pitching and yawing moments, and therefore on the capability to control attitude, have been analyzed at 100 km altitude. The aerodynamic behavior has been compared also with that of another aerospaceplane at 100 km both in clean and flapped configuration.

The present study focused on an experimental determination of damping ratio of a multi-storey building subjected to aerodynamic loadings. It used the methods of model construction, wind tunnel and dimensional analysis for the investigation. Although, the wind tunnel and dimensional analysis were successfully used in the past and in different ways by many Scholars and Engineers to investigate the problem of wind effects on buildings; but such solutions or efforts, did not include the influence of the building deflection (δ). The results of the study show that depending on the phase of the force with respect to motion, self-excited forces can be associated with the displacement, the velocity or acceleration of the structure. Due to the influence of these associations, these forces can be thought of as "aerodynamic contributions" to stiffness, damping and mass, respectively. The building deflection is therefore, considered to be an important structural quantity which affects structural quantities such as forces, moments, velocity and acceleration which severely affect the human perception criteria of occupants using multi-storey buildings. The damping ratio also proved to have been influenced by dependent variables such as stiffness, amplitudes of vibration, H/B ratio, Strouhal and L o numbers at a basic wind speed of 52.5 ms -1 . Therefore, it can also be inferred that the relationship in the variations of the values of H/B ratio and L o number are inversely proportional to the values of the Strouhal numbers and damping ratio along the model height. Whereas, the amplitude of the vibrations progressively increased, while, a critically damped model and its stiffness decrease with increase in model height. All these are likely to provide wider areas of applicability in structural analysis and in particular, experimental use of wind tunnel for structural modeling and similitude.

We formulate and solve data-driven aerodynamic shape design problems with distributionally robust optimization (DRO) approaches. Building on the findings of the work [13], we study the connections between a class of DRO and the Taguchi method in the context of robust design optimization. Our preliminary computational experiments on aerodynamic shape optimization in transonic turbulent flow show promising design results.

Scenario-basedmodeling (SBM) is an approach for creating executable models for reactive systems where each artifact specifies a separate aspect of overall system behavior. SBM has many advantages, including structural alignment with requirements, intuitiveness and incrementality, and it is available in visual languages (e.g., LSC), textual languages (e.g., Java, C++) and DSLs (e.g., SML). In this position paper, we argue that endowing the Statecharts visual formalism with SBM capabilities can significantly benefit software and system engineering, enhancing intuitive visualization of specifications and designs, and their scalability and amenability to formal verification. We demonstrate the position by amalgamating Statecharts and SBM within the YAKINDU Statechart Tools.

Bu çalışmada, Kahramanmaraş Sütçü İmam Üniversitesi Mühendislik ve Mimarlık Fakültesi tarafından TÜBİTAK Efficiency Challenge yarışlarına katılmak üzere tasarlanan elektrikli bir aracın aerodinamik özellikleri deneysel ve sayısal olarak incelenmiştir. Deneysel çalışmalar KSÜ Makine Mühendisliği Bölümü laboratuvarında bulunan rüzgâr tünelinde gerçekleştirilmiştir. Deneylerde kullanılan araç prototipinin ebadı; tünel kapasitesiyle bağlantılı olan blokaj oranı dikkate alınarak belirlenmiş ve araç prototipi 1/16 ölçekli olarak üretilmiştir. Deneysel çalışmalarda 7 farklı hava hızında (14.66/ 16.08/ 17.44/ 18.93/ 20.19/ 21.69/ 23.81) aracın maruz kaldığı sürüklenme kuvveti ölçülmüş ve sürüklenme katsayısı hesaplanmıştır. Sayısal çalışmalar ise Ansys programında gerçekleştirilmiştir. Bu çalışmalarda çözücü model olarak k-epsilon realizable modeli tercih edilmiştir. Artan hava hızlarına bağlı olarak sürüklenme kuvvetinin 0,1743 N ’dan 0,4014 N ’a kadar kademeli olarak arttığı tespit edilmi...

The aerodynamic and acoustic testing of a NACA0012 airfoil section was performed in an open wind tunnel, focusing on noise mechanisms at the trailing edge to identify and understand sources of noise production. The sound measurement profiles were captured by embedding microphones along the chord at various distances from the trailing edge and at different geometric angles of attack. The embedded microphones have successfully captured all noise sources due to aerodynamic flow over the NACA 0012 airfoil at the trailing edge, which included the following major peak frequencies: 44, 93, 166, and 332 Hz. The fundamental frequency of the model tested was identified by peak frequency (166 Hz). It appears that these frequencies do not deviate as the angle of attack is increased. The general trend is Strouhal numbers decrease as the flow moves downstream which indicates the amount of resonance (i.e. periodic, non-random vortices) decreases further downstream, which is to be expected given th...

The aerodynamic and acoustic testing of a NACA0012 airfoil section was performed in an open wind tunnel, focusing on noise mechanisms at the trailing edge to identify and understand sources of noise production. The sound measurement profiles were captured by embedding microphones along the chord at various distances from the trailing edge and at different geometric angles of attack. The embedded microphones have successfully captured all noise sources due to aerodynamic flow over the NACA 0012 airfoil at the trailing edge, which included the following major peak frequencies 44 Hz, 93 Hz, 166 Hz and 332Hz. The fundamental frequency of the model tested was identified by peak frequency (166Hz). It appears that these frequencies do not deviate as the angle of attack is increased. The general trend is Strohal numbers decrease as the flow moves downstream which indicate the amount of resonance (i.e. periodic, non-random vortices) decreases further downstream, which is to be expected given the onset of turbulence. Two bands of frequencies were identified. The frequency spectra between 1 to 3kHz show a measure of far field noise energy while frequency spectra in the range 3 to 10kHz shows near field noise energy which is due to mechanisms associated with wake flow (separation).

In the present study, two complex physical phenomena have been completely simulated and discussed in detail to predict the aerodynamic degradation and aeroacoustic mechanism of a NACA 0012 airfoil in both dry and heavy rain conditions. For this purpose, a CFD-based multiphase model was adopted to numerically investigate the process of formation of the water film layer on the airfoil surface by coupling the Lagrangian Discrete Phase Model (DPM) and the Eulerian Volume of Fluid (VOF) models. The Ffowcs Williams-Hawkings (FW-H) method was used to predict the aerodynamic noise of the airfoil in a heavy rain condition. The results showed that there were significant degradations of the airfoil aerodynamic performance because of water film formation especially at lower angles of attack. The maximum value of lift-to-drag ratio degradation was 56% at the angle of attack of 2°. Also, the Sound Pressure Level (SPL) increased due to the rain condition. The SPL was sensitive to the raindrop impact on airfoil surface and caused to increase SPL especially in the frequency region less than 2000 Hz. By increasing the angle of attack, the SPL increased especially in the high-frequency region higher than 2500 Hz in rain condition.

In the present study, special attention is paid to numerically investigate the aerodynamic performance of the NACA 0012 airfoil under rain and icing conditions with the aim to better understand the severe aerodynamic performance penalties of aircraft in flight. Furthermore, in order to control the flow separation and improve the aerodynamic performance of the airfoil under critical atmospheric conditions, the Gurney flap with different heights is attached to the trailing edge of the airfoil. The simulation is done at a Reynolds number of 3.1 × 10 5 under different atmospheric conditions including dry, rain, icing and coupling of rain and icing conditions. A two-way momentum coupled Eulerian-Lagrangian multiphase method is used to simulate the process of water film layer formed on the airfoil surface due to rainfall. According to the results, accumulation of water due to rainfall and ice accretion on the airfoil surface inevitably provides notable negative effects on the aerodynamic performance of the airfoil. It is concluded that icing induces a higher aerodynamic degradation than rain due to very intensive ice accretion. The Gurney flap as a passive flow control method with a favorable height for each condition is very beneficial. The maximum increment of the lift-to-drag ratio is achieved by Gurney flap with a height of 0.01 of airfoil chord length for dry and rain conditions and 0.02 of airfoil chord length for icing and coupling of rain and icing conditions, respectively. Airfoil • Flow separation • Aerodynamic performance • Gurney flap • Rain and icing • Multiphase method List of symbols μ Air dynamic viscosity u Air velocity vector c Airfoil chord length θ Angle between airfoil chord length and Gurney flap α Angle of attack ρ w Density of water D p Diameter of the rain particle Y + Dimensionless wall distance C D Drag coefficient β Drag force B Hesamoddin Salarian

This study explores the hydrodynamic and aerodynamic performance of a submarine and an airfoil under various angles of attack (AoA) using advanced computational fluid dynamics (CFD) simulations. The incompressible Reynolds Averaged Navier-Stokes (RANS) equations were solved using ANSYS, leveraging its segregated flow solver and adjoint optimization capabilities to automate the creation and meshing of computational domains. By analyzing velocity and pressure distributions across coarse and fine mesh resolutions, the research highlights the superior accuracy of fine meshes in capturing complex flow phenomena, such as flow separation, wake behavior, and velocity gradients. Submarine simulations with control surfaces revealed distinct symmetries and nearly zero maneuvering coefficients for specific configurations, filling gaps in the existing literature on fully appended geometries. Optimization efforts led to an enhanced design with improved aerodynamic efficiency, achieving reduced drag and stabilized flow, as validated by consistent performance at AoAs of 0°, 20°, and 80°. This work demonstrates the importance of fine mesh resolution, automated workflows, and adjoint solvers in accelerating the iterative design process and optimizing marine and aerodynamic structures for real-world applications. These findings highlight the significant influence of high attack angles on the submarine's vertical plane flow. Such insights offer a mechanical foundation for analyzing nonlinear motion phenomena during submarine surfacing. .

The falling of a plate is a simply posed problem that offers complex fluid-structure interactions. It also gives rise to different flow structures in relation to specific flight patterns of a plate such as autorotating tumble, side-to-side flutter, or constant abrupt turning in a chaotic manner depending on the Reynolds number and the non-dimensional moment of inertia In actual falling flights such as tree leaves and organisms, the bodies possess flexibility. Here, direct numerical simulation is used to portray the free fall of a flexible plate. The Navier-Stokes equations are solved via the upper-lower decomposition method. The effect of the flow on the solid plate is transferred through the immersed boundary method. A strictly spatially dependent stencil of the IB is adapted to provide a solution to the fourth-order beam equation via the pent-diagonal matrix algorithm. Comparing to the conventional method that couples with the temporal domain, this enables stability of solution through a range of bending rigidity k from k = 50 to k = 0.01. A plate with high stiffness resembles to a plate of non-flexible solution. The tumbling flight trajectory is found to change as a plate is more flexible, or as k is decreased. Further decrease in k result in changes flight states.

Mosquitoes have slimmer wings, higher flapping frequencies, and much lower amplitudes than most other insects. These unique features signify special aerodynamic mechanisms. Besides the leading-edge vortex, which is one of the most common mechanisms of flapping-wing flight, mosquitoes have two distinctive mechanisms: trailing-edge vortex and rotational drag. In this study, the three-dimensional flow field around a hovering mosquito is simulated by using the immersed boundary method. The numerical results agree well with previous experimental data. Mechanisms unique to mosquitoes are identified from the instantaneous pressure and vorticity fields. The flow domains, containing several vortical structures produced by the flapping wings, are divided into different regions for quantitatively analyzing the contribution of vortical structures to the lift. Advection of the trailing-edge vortex and production of the leading-edge vortex each contribute peaks in lift. Passive deformation of the...

This paper presents numerical simulations of the aerodynamic effects of trees on the flow field and dispersion of trafficoriginated pollutants in an urban street canyon of W/H = 1 with a perpendicular approach flow. Large Eddy Simulation (LES) is employed for the investigation and is validated against wind tunnel (WT) experiment. Comparisons is made between an empty street canyon and one containing avenue-like tree planting of pore volume, P vol = 96%. In the presence of trees, both measurements and simulations show considerably larger pollutant concentrations near the leeward wall and slightly lower concentrations near the windward wall in comparison to the tree-free case.

Aerodynamic parameters have a huge impact on the trajectory of a projectile which in turn results in its range and accuracy. The influence aerodynamic parameters for the estimation of trajectory elements are drag Coefficients, lift Coefficients, angles of attack, muzzle velocity, atmospheric conditions, and the projectile shape and size. Thus proper methods for determining the drag and lift forces of the projectile is very important. The trajectory of a projectile through the air is affected both by gravity and by aerodynamic forces. In this paper 57 mm and 37 mm anti aircraft projectile was considered for the analysis. Here main emphasis was given to determine pressure coefficient, Drag coefficients, lift coefficient of the projectiles at different angle of attack. To study the aerodynamic parameters the experiment was conducted in an open circuit subsonic wind tunnel where uniform flow velocity is maintained across the flow direction. For the experiment varied angles of the attack was considered. Here inclined manometer was used to find out the surface static pressure and the pressure coefficient was determined from that. Then the drag & lift forces and their coefficients was determined. Finally, for the computational analysis, the ANSYS Software was used to simulate the experimental data.

It is time to recall the past, the people who help me a lot in my research study over these years and to whom I should express my heartfelt appreciations for their contributions in bringing me to this stage. The years as a Ph.D. student at City University of Hong Kong really taught me a lot.

The aerodynamic performance of an aircraft can be enhanced by incorporating wingtip devices, or winglets, which primarily reduce lift-induced drag created by wingtip vortices. This study outlines an optimization procedure for implementing winglets on a Class I fixed-wing mini-UAV to maximize aerodynamic efficiency and performance. After the Conceptual and Preliminary design phases, a baseline UAV was developed without winglets, adhering to specific layout constraints (e.g., wingspan, length). Various winglet designs-plate and blended types with differing heights, cant angles, and sweep angles-were then created and assessed. A Computational Fluid Dynamics (CFD) analysis was conducted to evaluate the flow around both the winglet-free UAV and configurations with each winglet design. The simulations employed Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Spalart-Allmaras turbulence model, targeting the optimal winglet configuration for enhanced aerodynamic characteristics during cruise. Charts of lift, drag, pitching moment coefficients, and lift-to-drag ratios are presented, alongside flow contours illustrating vortex characteristics for both baseline and optimized configurations. Additionally, dynamic stability analyses examined how winglets impact the UAV's stability and control. The results demonstrated a significant improvement in aerodynamic coefficients (C Lmax , L/D max , C La , C ma), leading to an increase in both range and endurance.

One of the principal objectives of vibration isolation technology is to isolate sensitive equipment from a vibrating structure or to isolate the structure from an uncertain exogenous disturbance source. In this paper, a dynamic observer-based active isolator is proposed that guarantees closed-loop asymptotic stabil- ity and disturbance decoupling between the vibrating structure and isolated structure. The proposed active isolator is applied to a uniaxial vibrational system and compared to an optimal linear-quadratic design.

A high voltage switch tube with a central cathode cy lindrically symmetric to and surrounded by a tubular anode, with a grid interposed between the cathode and anode. A high negative voltage is applied to the cath ode, but the flow of electrons to the anode is blocked by the grid which is held near cathode potential. After a space charge is created at the grid by electrons from the cathode, the grid is pulsed to ground potential, releasing electrons from the cathode to yield a very high current pulse. The cathode is preferably a graphite foam sleeve mounted on a support structure.

Accurate predictions of the blade response in a multi-row compressor is one of the most important tasks within the design process of compressor blades. Some recent studies have shown that the decoupled method considering only the stator disturbances cannot obtain accurate results for cases with strong rotor–stator interactions, especially for the interaction between the rotor and downstream stator, and the coupled method with multi-row configurations is necessary. Factors determine what computational domains to model need to be clarified to find a balance between accuracy requirements and computational costs. To this end, this study conducted full-annulus unsteady calculations with decoupled and coupled configurations to investigate the forced response of an embedded compressor rotor induced by upstream and downstream stator disturbances and rotor–stator interactions, respectively. The results show that the upstream IGV disturbances were dominated by the wake, and the IGV and S1 pot...

This paper examines the tracing of the trajectories of weak waves behind a shock wave induced flow in order to establish how the domain shape influences the flow both from a spatial and temporal perspective. The basic principle is that if a particle produces a series of point disturbances in a flow field the perturbations induced will propagate outwards at the local sonic velocity whilst at the same time being convected along with the local flow velocity. A number of issues may be identified for an unsteady flow. Firstly the flow field at later times may be influenced by perturbations produced at earlier times. Secondly, if the positions of the perturbations can be monitored as a function of time then the trajectory and velocity of the particle may be deduced. Thirdly, if a perturbation arises from a point on a boundary then its influence, if any, on any particular part of the flow can be established.

A predominantly experimental investigation into the nature of transonic flow within an aerodynamic corner is treated. The work focuses on exploring the shock-induced separation that can occur due to the corner. Effects of dihedral angle, and sharp and filleted 90 o corners were studied on a RAE2822 profile wing. Tests were conducted in a shock tube operating as a short-duration transonic tunnel, using oil-film surface flow visualisation techniques. The experimental results are compared to numerical simulation studies. The CFD results correlate well with the experiments. It is shown that a fillet radius disperses the region of separated and reversed flow outwardly from the centre of the corner. Increasing the dihedral angle of the corner significantly delays and weakens the separated region.

In the reflection of shock waves off a surface von Neumann’s theory assumes compressible and inviscid flow. It also assumes the reflecting surface to be perfectly smooth, nonporous, and adiabatic. It is found to be accurate for a wide range of regular reflection patterns and limited to very strong shocks in the case of Mach reflection. However experiments have shown that regular reflection persists beyond the theoretical limit. It has been postulated that this is due to the development of a viscous boundary layer behind the reflection point, an explanation now well accepted. However, the assumption of an adiabatic wall has persisted over many years. An experiment has been devised where two inclined surfaces on either side of a symmetry plane and impacted by a propagating shock wave normal to the plane would show any differences in reflection behaviour, if they were equally smooth but of different conductivities. Tests were conducted at incident shock Mach numbers from 1.30 to 1.59, ...

This paper examines the tracing of the trajectories of weak waves behind a shock wave induced flow in order to establish how the domain shape influences the flow both from a spatial and temporal perspective. The basic principle is that if a particle produces a series of point disturbances in a flow field the perturbations induced will propagate outwards at the local sonic velocity whilst at the same time being convected along with the local flow velocity. A number of issues may be identified for an unsteady flow. Firstly the flow field at later times may be influenced by perturbations produced at earlier times. Secondly, if the positions of the perturbations can be monitored as a function of time then the trajectory and velocity of the particle may be deduced. Thirdly, if a perturbation arises from a point on a boundary then its influence, if any, on any particular part of the flow can be established.

Advanced manufacturing engineering is an approach to build an object with the inclusion of all technical aspects including durability as well as safety. In automobile manufacturing approach,It can be a great opportunity to save life of occupant if safety parameters were designed successfully. Commercial passenger vehicles can carry several people at a time, and if accident happens, several people can die altogether. These types of vehicle can have collision from different side i.e. front, side, rear etc. Among this directional collision frontal impact is the most severe one. In front impact passenger can get injuries by hitting the seat structure mounted just next front to them. In order to design these seats properly to avoid these injuries, government also enforced some regulations related to seat design. In order to pass the compulsory regulations, properly designed seat has to be sent to the government agency to have to test certificate. Advanced simulation tools can also assist...

In this study, design calculations and calculations of afterburner used in jet engines are presented by evaluating the results of analytical and computational analysis. Afterburner inlet values of 1050 K temperature, 300 kPa pressure and 3.6 kg/s mass flow rate are taken as the design conditions. Maximum length and diameter are 500 mm and 200 mm, respectively, for the sections to be designed as length constraints within the scope of the conceptual design. The tworing vee-gutter has 1.33 cm in diameter and 4.25 cm high. Jet A fuel is assumed to be injected into the core flow (90 degrees) from the spray bars. The spray is mounted in line with the veegutter to optimize the mixing of the flow. Analyses are performed for 4 cm between the spray bar and the vee-gutter. For the study, the GE J79 engine was examined from the literature and taken as a basis for the aerodynamic transition section design. Within the scope of TEKNOFEST 2023 Jet Engine Design Competition, a preliminary design of an afterburner module that can produce 700 pounds of thrust and has a life capacity of 25 hours should be realized in line with the design requirements and constraints. In the light of geometric constraints, one-dimensional combustion calculations of the module are made, and the parts are modelled using the relevant SolidWorks CAD program and these modelled parts are then transferred to ANSYS™ environment and the results and analyses are verified. The afterburner module flow analysis software program ANSYS™ is used to analyse the afterburner operation in both cold operating ranges (i.e. without combustion) using compressible, viscous and standard k-epsilon turbulence model. As a result, the effect of afterburner length on combustion performance is found to be significant. As a result of the calculations, afterburner length is found as 28.14 cm. It is found that the combustion efficiency is 81.5% and the temperature can be increased from 1050 K to 2044 K. The total pressure loss is 14.96% as pressure drop due to the geometric parameters and heat addition. The blockage ratio calculated due to the use of vee-gutter geometry is the most important parameter in the pressure drop. It is found that the jet engine producing 670 lbs (2981 N) of thrust when the afterburner is not working whereas it can provide a significant amount of power increment at the expense of a 50% increase in specific fuel consumption when the afterburner is active as well as providing a 738 lbs (3238 N) with a 10.1% thrust increase. The reason of the enhancement is mainly coming from the mixing effect of the vee-gutter on the flow structure.

Scale model wind tunnel testing was used to investigate the effect of parapets on the wind loading of a roof-top solar array with a tilt angle of 101. Previous studies have indicated a correlation between parapet height and uplift wind loads acting on roof membranes and roof-top equipment. This relationship was reproduced in the current study for wind loads acting on roof-top solar arrays and is shown to be caused by building-induced aerodynamics, namely corner vortices. Increasing parapet height was shown to increase the peak wind loads acting on the array. These increases were found to be dependent on location on the roof, in the array, and geometry of the array itself. The parapet effect results in peak wind load increases for much of the array for typical parapet heights when all wind directions are considered.

The modeling, control, and dynamic stabilization of long-span suspension bridges are considered. By employing leading- and trailing-edge flaps in combination, we show that the critical wind speeds for flutter and torsional divergence can be increased significantly. The relatively less well known aerodynamic properties of leading-edge flaps will be studied in detail prior to their utilization in aeroelastic stability and control system design studies. The optimal approximation of the classical Theodorsen circulation function will be studied as part of the bridge section model building exercise. While a wide variety of control systems is possible, we focus on compensation schemes that can be implemented using passive mechanical components such as springs, dampers, gearboxes, and levers. A single-loop control system that controls the leading- and trailing-edge flaps by sensing the main deck pitch angle is investigated. The key finding is that the critical wind speeds for flutter and to...

This paper presents the design, modeling and analysis of a morphing trailing edge (TE) flap for a large aircraft high lift wing. Attention was firstly focused on the design of an actuation system to smoothly deflect the flexible rear part of the flap to achieve a specified shape. An existing curved beam eccentuator design was adapted to the current structure together with an open sliding trailing edge. Additional connections were set between the upper and lower skins to ensure the integrity of the flap structure, under the aerodynamic and actuation loads, was maintained. Different types of connections were investigated and modeled to represent the practical design case. The effects of the aerodynamic pressure load on the flap structure and on the actuation load were analyzed. Subsequently a nonlinear structural modeling and analysis of the flap TE were carried out. A stress and strain analysis was performed to ensure a safe design and also to study the TE flap mechanical behavior under both actuation and aerodynamic load. The results showed that the proposed design solution is simple and able to achieve the desired flap morphed shape.

This paper presents the design, modeling and analysis of a morphing trailing edge (TE) flap for a large aircraft high lift wing. Attention was firstly focused on the design of an actuation system to smoothly deflect the flexible rear part of the flap to achieve a specified shape. An existing curved beam eccentuator design was adapted to the current structure together with an open sliding trailing edge. Additional connections were set between the upper and lower skins to ensure the integrity of the flap structure, under the aerodynamic and actuation loads, was maintained. Different types of connections were investigated and modeled to represent the practical design case. The effects of the aerodynamic pressure load on the flap structure and on the actuation load were analyzed. Subsequently a nonlinear structural modeling and analysis of the flap TE were carried out. A stress and strain analysis was performed to ensure a safe design and also to study the TE flap mechanical behavior under both actuation and aerodynamic load. The results showed that the proposed design solution is simple and able to achieve the desired flap morphed shape.

In this paper, investigation was made into the design, experiment, and aerodynamic analysis of a novel flapping wing rotor applicable to micro aerial vehicles (MAV). Attention was firstly focused on the design of a simple, reliable and lightweight flapping rotor configuration and wing structure to meet the challenging demands for high mechanical and power efficiency and vertical take-off and landing (VTOL) capability of an MAV. The experimental work demonstrated the feasibility and effectiveness of the innovative design. The paper presents an approach of experiment and processing the measured flapping wing total dynamic forces to extract the unsteady aerodynamic force. A potential-flow-based method, unsteady panel method was used to calculate the lift created by flapping wing system. As the method is two dimensional, strip theory is adopted to evaluate the aerodynamics of three dimensional flapping wings. Compared with measured data, the numerical results show good agreement with the first order lift component, which is caused by the rigid wing.

The aerodynamics and also noise produced by aeroengines is a critical topic in engine design. Hybrid Reynolds-Averaged Navier-Stokes-Large-Eddy Simulation (RANS-LES), is used to investigate the influence of upstream internal geometry on jet flow and noise. The methods are validated using an isolated nozzle. Internal geometry is added using approximated Immersed Boundary Methods (IBMs) and Body Force Methods (BFMs) reducing grid complexity and cost. Installed coaxial nozzles including an intake, wing and flap and internally, the fan, outlet guide vanes (OGVs) and other large

Conocer el comportamiento del flujo alrededor de pares de cilindros circulares es de gran importancia practica en muchas areas de la ingenieria. En este trabajo se investiga numericamente la interferencia de flujo entre dos cilindros dispuestos uno detras de otro (tandem) para un numero de Reynolds Re=1.2e05. El flujo turbulento tridimensional y dependiente del tiempo alrededor de los cilindros es simulado numericamente utilizando el modelo de turbulencia SAS (Scale-Adaptive Simulation) por medio del codigo Fluent, que implementa el metodo de volumenes finitos. El solver empleado es el algoritmo SIMPLE (Semi Implicit Method for Pressure Linked Equations) con un esquema bounded second-order implicit para resolver la formulacion transitoria. La distancia de centro a centro entre los cilindros (L) varia desde 1.2 a 6 diametros (D) del cilindro, a fin de identificar los efectos de interferencia de estela debido a la proximidad entre los cilindros. La dinamica de vortices y las fuerzas a...

A fin de mejorar el diseno racional de estructuras fijas, resulta necesario estudiar la accion del flujo de aire alrededor de las mismas. Tal es el caso de los tanques y silos de almacenamiento, donde la estimacion de las acciones debidas al viento y sus consecuencias, inciden en el diseno y optimizacion estructural. En este trabajo se presenta un analisis numerico por medio de dinamica de fluido computacional (CFD) del campo de movimiento alrededor de un tanque metalico con el objetivo de obtener la distribucion de presiones de viento sobre el mismo. El estudio se realiza mediante el uso del programa comercial Ansys Fluent que implementa el metodo de volumenes finitos. La validacion del codigo se realizo mediante la reproduccion numerica del flujo alrededor de una esfera para distintos numeros de Reynolds. Seguidamente se desarrollaron modelizaciones numericas del flujo de viento actuando sobre un tanque cilindrico del que se tienen datos experimentales en tunel de viento. Los resu...

It is well known that openFoam has become a very popular tool for research work in different fields and particularly, in fluid dynamics. But, it is also known its lack of detailed documentation supporting solvers made using the set of libraries provided by openFoam. Therefore, it becomes necessary to establish appropriate verifications that can be useful to users going for instance, through the selection of equations discretization schemes from fvSchemes libraries and of solution solvers from fvSolutions libraries, to be later applied in the simulation of a given specific problem. With this purpose, executable solvers available in openFoam 1.7 version to solve supersonic air flow problems are tested. Two different approaches have been taken in developing numerical methods to solve problems in transport phenomena at all Mach numbers and traditionally, they have been referred to as pressure-based and density-based methods. In this work, the advantages or disadvantages in applying any ...

One of the key issues in a reentry risk analysis is the calculation of the aerodynamic coefficients. This paper presents a methodology to obtain these coefficients and couple it to a code that computes re-entry trajectories considering six degrees of freedom. To evaluate the different flight conditions encountered during the natural re-entry of conical objects, the Euler Equations for gasdynamics flows are used. A new scheme TVD (Total Variation Diminishing) is incorporated to a finite volume unstructured cell-centred formulation, for application to three-dimensional Euler flows. Finally, numerical results are obtained for a conical body at different attack angles and Mach. With these results, the calculation of the trajectories during atmospheric re-entry is completed.

Wind energy is one of the biggest sources of renewable energy in Canada that accounts for 3.5 percent of electricity generation. However, icing on the blades during the cold seasons can cause some serious problems. This can apply extra inertia and makes the rotary system unbalanced which can damage the turbine. Furthermore, it changes the aerodynamic shape of the blades and changes the lift and drag coefficient of the wind turbine blades which reduces the generated power. To study the effects of the ice layer growth on the aerodynamic behavior of the blade, a 2D airfoil of NACA 64(3)-618 which is a common airfoil used in wind turbines is considered. In this study, the turbulent flow over the airfoil with an iced layer on the leading edge is modeled. The k-ω SST model is used to simulate the turbulent flow and OpenFOAM CFD package is utilized to integrate the governing equations. The flow behavior around the airfoil with and without the icing layers is studied for the Re equal to 137,000 when the angle of attack is changed from 0 to 15 degree. It is expected that according to the changes in the airfoil shape in the presence of the icing layer which is a destructive phenomenon, the lift coefficient decreases and the drag coefficient increase. Also, it is expected that icing can affect the separation point and advances it.

Tall buildings are particularly prone to dynamic excitations such as those from natural disasters like strong winds and earthquakes, and this has become an especially important design issue with manhattanization. One way to minimize wind-induced vibrations of tall buildings is to focus more on their shapes in the design stage. This paper investigates variations in along-wind and crosswind overturning moment coefficients, power spectral densities, and trajectories of various wind force coefficients.

Recent tall buildings tend to have unconventional shapes as a prevailing, which is effective for suppressing across-wind responses. Suppression of across-wind responses is a major factor in tall building projects, and the so called aerodynamic modification method is comprehensively used. The purpose of the present study is to investigate the pressure fluctuations on tapered and setback tall buildings, including peak pressures, power spectra and coherences through the synchronous multi-pressure sensing system techniques. And flow measurements around the models were conducted to investigate the condition of vortex shedding. The results show that by tapering and setback, different distributions of mean pressure coefficients at leeward surface were found, which is caused by the geometric characteristics of the models. And the power spectra of wind pressures at sideward surface become wideband and the peak frequencies are different depending on heights, which makes the correlation near the Strouhal component low or even negative. The differences in shedding frequencies were also confirmed by the flow fields around the models.

In the present study, we investigated a new type of non-uniform surface cylinder based on a harbor seal vibrissa to reduce aerodynamic forces and suppress vortex shedding. Three vibrissa-based bionic cylinder models (i.e., models #1, #2, and #3) with different undulation wavelengths were manufactured and tested in a wind tunnel. The wind tunnel experiments were conducted at a Reynolds number of Re ≈ 50000 based on the hydrodynamic diameter (D h ) and incoming airflow speed. The control effects on the aerodynamic forces and flow structures around the bionic cylinders were studied and compared with those of a baseline circular cylinder. In addition to measuring the surface pressure distributions using an array of digital pressure transducers, a high frequency force balance was used to determine the aerodynamic forces acting on the test models. Moreover, a digital particle image velocimetry (PIV) system was utilized to quantify the stream-wise flow structure and span-wise flow field to assess the effectiveness of the bionic cylinder models. The results revealed that a bionic non-uniform surface distribution could reduce the mean drag and suppress the fluctuating lift to a certain extent. Bionic cylinder model #2, which had a wavelength of two minor axes, worked best among the three models, and it was found to achieve a drag reduction of 15% and a maximum fluctuating lift suppression of 58% when the angle of the incoming airflow was 0°. The PIV results indicated that the non-uniform surface structure would disrupt the consistency of span-wise flow and decrease the span-wise correlation in the near wake of the test models, which could decrease the turbulent kinetic energy, mean drag, and fluctuating lift of the test models.

This study presents a new approach for identification of aerodynamic damping of tall buildings from stochastic crosswind response time history using unscented Kalman filter (UKF) technique. The system damping ratio is expressed as a polynomial function of building displacement or velocity, which is equivalent to a polynomial function of amplitude of harmonic motion. The structural system with nonlinear system damping under stochastic excitation is modeled as a single degree of freedom system with a white noise input. The augmented state variables of the system, which also include unknown system frequency, damping and stochastic excitation parameters, are estimated simultaneously with the UKF technique from the response measurement data. The aerodynamic damping is then extracted from the system damping by subtracting the structural damping. Firstly, the stochastic response time histories of a tall building model at various wind speeds with a known nonlinear aerodynamic model are simulated and the performance of the UKF technique and the influence of selections of various parameters involved are investigated. Secondly, the aerodynamic damping of a square-shaped tall building is identified based on aeroelastic building model wind tunnel test data. The response statistics are then computed using the identified damping and compared with the measurement data to verify the accuracy of identification.