Aerodynamics

In present study, an investigation has been carried out for the unsteady turbulent flow over various type of cylinders. Reynolds-Average Navier-Stroke (RANS) equations along with SST (Shear Stress Transport) model are solved using finite element method in order to study the variation of aerodynamics forces. Linear triangular mesh elements are used for the grid generation of the computational domain. Simulation is performed at a high Reynolds number of Re=1,00,000 based on the free stream velocity and diameter of the cylinder. Influence of change of angle of attack on aerodynamic forces is examined. Results shows, the rectangular cylinder show maximum variation of drag and lift with the change of angle. The wake region behind the cylinders are also observed.

Aiming to limit the forced response of an axial turbine blisk for ship Diesel engine applications efforts have been made to increase the aerodynamic damping contribution for the most critical modes. In this regard the potential of intentional mistuning is investigated since it offers the opportunity to ensure a safe operation without a severe loss of aerodynamic performance. Genetic algorithms have been chosen to derive an optimized mistuning pattern. In order to keep the manufacturing effort within a limit only two possible blade geometries are allowed which means that an integer optimization problem has been formulated. For the purpose of demonstrating the benefit of the intentional mistuning pattern found, two blisk prototypes have been manufactured: One with and another one without employing intentional mistuning for purposes of comparison. Furthermore, this offers the opportunity for an experimental determination of mistuning being really manufactured and other modal properties as well. The experimental data basis is employed to update structural models which are well suited to demonstrate the forced response reduction under operational conditions.

Maintaining an upright stance requires the integration of sensory inputs from the visual, vestibular and somatosensory-proprioceptive systems by the cortex to develop a corrective postural strategy. However, it is unclear whether and how the cerebral cortex monitors and controls postural sways. Here, we asked whether postural sways are encoded in ongoing cortical oscillations, giving rise to a form of corticokinematic coherence (CKC) in the context of standing balance. Center-of-pressure (CoP) and center of mass (CoM) fluctuations and electroencephalographic cortical activity were recorded as young healthy participants performed balance tasks during which sensory information was manipulated, by either removal or alteration. We found that postural sways are represented in ongoing SM1 cortical activity during challenging balance conditions, in the form of CKC at 1–6 Hz that was stronger for CoP compared with CoM fluctuations. Time delays between cortical activity and CoP features indi...

An understanding of the aerodynamic and biophysical properties of barley malt is necessary for the appropriate design of equipment for the handling, shipping, dehydration, grading, sorting and warehousing of this strategic crop. Malting is a complex biotechnological process that includes steeping; germination and finally, the dehydration of cereal grains under controlled temperature and humidity conditions. In this investigation, the biophysical properties of barley malt were predicted using two models of artificial neural networks as well as response surface methodology. Stepping time and germination time were selected as the independent variables and 1 000 kernel weight, kernel density and terminal velocity were selected as the dependent variables (responses). The obtained outcomes showed that the artificial neural network model, with a logarithmic sigmoid activation function, presents more precise results than the response surface model in the prediction of the aerodynamic and bi...

The results of the simulation and development of an aerodynamic platform for pre-flight testing of nanosatellites and Unmanned Aerial Vehicles are presented. The platform movable part is realized in the form of a regular hexagonal prism with a honeycomb hollow structure. It provides levitation conditions and allows a check of the attitude control system performance. The airflow dumping elements of the air injection subsystem which provides platform stability are suggested. The aerodynamic platform model is developing as part of a project to introduce practical elements of prototyping and pre-flight testing of nanosatellites and Unmanned Aerial Vehicles into the educational process. It will help university students to solve scientific and technological problems.

An improved hybrid adjoint method to the viscous, compressible Reynold-Averaged Navier-Stokes Equation (RANS) is developed for the computation of objective function gradient and demonstrated for external aerodynamic design optimization. In this paper, the main idea is to extend the previous coupling of the discrete and continuous adjoint method by the grid-node coordinates variation technique for the computation of the variation in the gradients of flow variables. This approach in combination with the Jacobian matrices of flow fluxes refrained the objective function from field integrals and coordinate transformation matrix. Thus, it opens up the possibility of employing the hybrid adjoint method to evaluate the subsequent objective function gradient analogous to many shape parameters, comprises of only boundary integrals. This avoids the grid regeneration in the geometry for every surface perturbation in a structured and unstructured grid. Hence, this viable technique reduces the overall CPU cost. Moreover, the new hybrid adjoint method has been successfully applied for the computation of accurate sensitivity derivatives. Finally, for the investigation of the presented numerical method, simulations are carried out on NACA0012 airfoil in a transonic regime and its accuracy and effectiveness related to the new gradient equation has been verified with the Finite Difference Method (FDM). The analysis reveals that the presented methodology for the optimization provides the designer with an indispensable CPU-cost effective tool to reshape the complex geometry airfoil surfaces, useful relative to the state-of-the-art; in a less computing time.

A Parabolised Navier-Stokes (PNS) flow solver is used to predict the aerodynamic heating on the surface of a hypersonic vehicle. This case study highlights some of the main heat flux sensitivies to various conditions for a full-scale vehicle and illustrates the use of different complimentary methods in assessing the heat load for a realistic application. Different flight phases of the vehicle are considered, with freestream conditions from Mach 4 to Mach 8 across a range of altitudes. Both laminar and turbulent flows are studied, together with the effect of the isothermal wall temperature, boundary-layer transition location and body incidence. The effect of the Spalart-Allmaras and Baldwin-Lomax turbulent models on the heat transfer distributions is assessed. A rigorous assessment of the computations is conducted through both iterative and grid convergence studies and a supporting experimental investigation is performed on a 1/20th scale model of the vehicle’s forebody for the valid...

In turbomachinery CFD simulations, Reynolds-Averaged Navier-Stokes (RANS) based approaches have a tendency to under predict the mixing of wakes, tip leakage flows and other secondary flow features formed in the endwall region, for example, corner separations in axial compressors, while at the same time over predicting their size. This has a dramatic impact on the performance predictions, which stems from poor prediction of spanwise profiles of total pressure or total temperature, where RANS typically yields more coherent features and much stronger undulations than experimental data. The hybrid RANS/LES methods (i.e. various DES formulations), with RANS modeling of the flow near the wall, and eddy-resolving simulation away from the wall, help to better represent the mixing in turbulent flows. Our previous work with DES models in a linear compressor cascade also showed that prediction of corner separation and thus loss profile can be greatly improved when unsteadiness outside of the boundary layer region is also resolved [1]. In high pressure turbine simulations with DES models, improvement in the mixing of the horseshoe vortex and the tip leakage vortex also leads to much improved loss profile predictions. The original DES model suffers from pre-mature boundary layer separations. This is solved in the delayed-DES (or DDES) model, in which a sheltering function is added to prevent pre-mature separation. However, the DDES model also under predicts the mixing in the shear layers, particularly right close to the onset of the shear layer. This may be attributed to the lack of upstream turbulence fluctuation from a RANS boundary layer solution. However, due to the strong upstream turbulence kinetic energy, the RANS zone extends farther downstream than desired, due to the smaller turbulence length-scale as dictated in the DDES model formulation. The Kevin-Helmholtz instability does not start to develop until the RANS zone ends. The delayed transition to LES mode in the shear layer also leads to undesired mixing in the turbomachinery simulations. Specifically, the mixing in the wake of the blade and in the tip leakage flow is slow. The shear-layer-adapted (SLA) model within the framework of SA-DDES, aiming to unlock the Kevin-Helmholtz instability in the initial stage of the shear layer, addresses this issue [2]. SLA-DDES model uses the Vortex Tilting Measure (VTM) to detect the shear layer, and defines a new subgrid length scale that activates the LES model sooner. SLA-DDES model has also been reported to provide improvements in plane shear layer flows. In this work, the SLA-DDES concept has been adopted in the context SST k-omega based DDES model. The model has been tested in canonical cases, and applied to turbomachinery flows. In Figure , the tip clearance flow in a compressor rotor DES simulation is shown. The isosurfaces of the Q criterion are plotted. In the original DDES model, the transition from RANS to LES is slow, and the RANS-like convection of the leakage flow vortices starting from the leading edge can be seen. In the SLA-DDES model, more eddies are resolved as the transition to LES is much faster. In the final paper, detailed comparison of the simulation from both models with the test data will be included.

This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with an LPT stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure-distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic ...

A good aerodynamic design of the turbine rear structure (TRS) is crucial for improving efficiency and reducing emissions from aero-engines. This paper presents a detailed experimental evaluation of an engine realistic TRS which was studied in an engine-realistic rig at Chalmers University of Technology, Sweden. The TRS test section was equipped with three types of outlet guide vanes (OGVs) which are typical of modern state-of-the-art TRS: regular vanes, thickened vanes and vanes with an engine mount recess (a shroud bump). Each of the three vane geometries were studied under on-design and off-design conditions at a fixed flow Reynolds number of 235,000. The study shows that the off-design performance of the TRS strongly depends on the presence of the local flow separation on the OGV suction side near the hub, which is greatly affected by the vane pressure distribution and inlet conditions. Similarly, the OGVs with increased thickness and with a vane shroud bump are shown to affect t...

This paper describes a new control approach for scale-model airplanes. The proposed control solution is primarily geared towards drones whose lift surfaces can be approximated by a disc-shaped wing. Designed and analysed on the basis of a specific model of aerodynamic forces acting on the aircraft, it departs from other solutions in its capacity to handle important and rapidly changing attack angles within a large flight envelope. Simulation results illustrate its robust performance.

This paper proposes a control design strategy, encompassing trajectory tracking and path following, for a category of convertible aircraft with fixed wings and vectorized thrust, as exemplified by the Harrier jet aircraft and the V-22 Osprey. The approach relies on, and extends, previous works on the control of hovering vehicles (helicopters, quadrotors,...), axisymmetric devices (rockets, missiles,...), and fixed-wing aircraft (airplanes). In particular it exploits a common nonlinear model of aerodynamic forces exerted on the vehicle, both simple and representative of the underlying physics. Besides the unifying property of this approach, the proposed solution addresses the delicate transition problem between hovering and cruising flight, and thus the concomitant thrust tilting issue, in a novel manner with the possibility of continuously minimizing the thrust intensity, and thus energy expenditure.

This paper addresses the path following control problem for scale-model fixed-wing aircraft. Kinematic guidance and dynamic control laws are developed within a single coherent framework that exploits a simple generic model of aerodynamic forces acting on the aircraft and applies to almost all regular 3D paths. The proposed control solutions are derived on the basis of theoretical stability and convergence analyses. They are complemented by addressing several practical issues, and validated via realistic hardware-in-the-loop simulations.

The geometry of commercially available wheel hub motors inherently restricts packaging space and may prevent the introduction of more sophisticated, efficient, and expensive cooling systems. Due to the limited available space in the wheels, commercial hub motors often rely on aerodynamic passive cooling. The small air-gap (0.5-1 mm) between the coils and the magnets results in heat transfer to the magnets and consequently increases their temperature. As a result, the perfeormance of the permanent magnets (PMs) will be limited and also will heavily affect their lifetime; thus, advanced cooling strategies must be introduced. In the current study, a three-dimensional (3D) thermal model was developed for a commercially available 500 W scooter hub motor under a constant heat load of 180 W using Computational Fluid Dynamics (CFD) (= 64%).The spatial distribution of the temperature for the motor parts are evaluated considering both the internal and external fluid flow dynamics. Further, analysis of airflow in the the gap is performed and the results from the CFD is compared with the published correlations. The flow in such small motor was found to be laminar with Taylor number below 40. Results also showed that enhancement of the cooling is necessary to avoid damage of the winding vernish and to reduce the magnets temperature particularly when the motor works at high torque with low efficiency.

The aeronautics studies and particularly the development of drones represent an important field, in which there is a very large number of research and studies.This article aims to present an experimental aerodynamic study of an autonomous surveillance unmanned aerial vehicle (UAV) that is capable of combining the advantages of both categories, namely the fixed-wing drones and the rotary-wing drones. To achieve this objective, a wind tunnel was used to study the flow around this drone in order to better understand the aerodynamic phenomena and to obtain some initial estimates of the lift, drag and moment coefficients, at three different Reynolds numbers of 4.02×104, 6.03×104 and 8.04×104, and for different angles of attack, from [−45°, +45°] with step of 1°.The experimental results obtained in this work show an casi-symetrical variation bertwen the negatif and positif incidence angles of the lift coeffecient, wiche indicate that the heliplane can fly in an inverted position, whatever...

A new optimized winglet of a small aircraft is used to develop the solutions for structure, VHF antenna, systems as lights and lightning protection. The aerodynamic optimization has been based on the Design of Experiment and Response Surface method in order to find out the suitable shape of the winglet from the aerodynamic, structure and the basic operating frequency range for VHF radio communication points of view. The winglet's structure has been designed based on the aerodynamic loads and took into account the appropriate technology. The improvement of the aerodynamic characteristics and handling qualities of the aircraft are discussed and the integration concepts and production moulds are presented.

This work deals with a general boundary-element methodology for the solution of the wav(' e(luation around objcrts lIIoving in arbitrary motion, with applirations to unsteady pot('ntial ('ompressible a('rodyn8miC's of streamlined bodies (surh as airplanes and hdicopters). The paper indudes the derivation of the boundary integral equation for the wave ('quation. for a frame of refer('nce moving in arbitrary motion (in particular, in translation and in rotation). Also induded are (i) a discussion of the formulation for th(' analysis of th(' lIIotion of til(' wake, and (ii) the boundary-d('lIu'nt algorithm used for the computational impl(•Ill('ntation. Validation of the formulation is presmted for the rases of airplane wings and helicopter rotors. The test rases fall into two categories: presC'rih(•d-wake and fr('e-wake analyses. The validation of the prescribed-wake analysis is pres(•nl<•d for rompr('ssibl(' flows (suhsonic for h('licopt('r rotors. transonic for airplaJl(•s). The nUlllerical validation of the free-wake analysis of hdicopt<•r rotors is pn's('nted for incompressible flows. Th. A. Cruse (Editor) Advanced Boundary Element Methods

A careful study of accuracy and performance is carried out for highorder solutions of compressible flows. The Spectral Finite Volume method is employed to solve the 2-D Euler equations in a unstructured, finite volume context with implicit time march algorithms. The use of high-order schemes for spatial discretization is of great interest to engineering problems since it holds the potential to reduce simulation costs and improve quality of the solution. The work presented here address common issues related to highorder schemes such as the treatment of flow discontinuities, efficient time march schemes, proper geometry and mesh representation and verification of the solution obtained.

This research focuses on calculating the force distribution on the wings of the LSU 05-NG aircraft by several numerical methods. Analysis of the force distribution on the wing is important because the wing has a very important role in producing sufficient lift for the aircraft. The numerical methods used to calculate the lift force distribution on the wings are Computational Flow Dynamics (CFD), Lifting Line Theory, Vortex Lattice Method and 3D Panel Method. The numerical methods used will be compared with each other to determine the accuracy and time required to calculate wing lift distribution. Because CFDs produce more accurate estimates, CFD is used as the main comparison for the other three numerical methods. Based on calculations performed, 3D Panel Method has an accuracy that is close to CFD with a shorter time. 3D Panel Method requires 400 while CFD 1210 seconds with results that are not much different. While LLT and VLM have poor accuracy, however, shorter time is needed. T...

The development of Unmanned Aerial Vehicle (UAV) technology in both developing and developing countries is accelerating. In particular, UAV technology innovation for maritime affairs. The Aviation Technology Center has developed several UAVs used for the Maritime Surveillance System (MSS), which are marine surveillance and operations systems based on the use of UAV technology. Until now, several UAV variants have been developed, one of which is being developed is the LSU 05-NG. The main target of the design of the LSU 05-NG is to get a UAV as a lightweight utility platform and can operate in the marine environment and near the sea. Therefore it is necessary to do a static and dynamic analysis to determine the performance of the LSU 05-NG flight. In this paper using the numerical method VLM, CFD and DATCOM to analyze the aerodynamic characteristics of LSU 05-NG. Based on the results of the analysis of the values of C L , C D , C M , C n ,and C l , it can be concluded that LSU 05-NG has static stability. Because the values C Mα < 0, C l β < 0 and C n β > 0.

Pada perancangan pesawat terbang tanpa awak, pemilihan airfoil sangat penting untuk meningkatkan performa pesawat. Airfoil dipilih berdasarkan karakteristik geometri dan performa aerodinamikanya. Penelitian ini membahas tentang pemilihan airfoil dengan banyak kriteria berdasarkan karakteristik masing-masing airfoil. Pada tahap awal, sebanyak 1504 airfoil tersaring menjadi 5 airfoil terpilih. Airfoil tersebut dianalisis berdasarkan 7 kriteria utama, yaitu Camber, Thickness, Manufacturability, Max C_L, C_(L_0 ), Max C_L angle, dan Max L/D. Berdasarkan analisis tersebut, FX 76-MP-160 terpilih sebagai airfoil terbaik untuk pesawat terbang tanpa awak yang dirancang.

Framework Flutter yang menggunakan bahasa pemrograman Dart dalam pengkodeannya. SDK atau framework open source Flutter dibuat oleh Google untuk membantu pengembang membuat atau mengembangkan aplikasi yang berjalan pada sistem operasi Android dan iOS. Karena statemanagement system pada intinya adalah sebuah teori, ada banyak statemanagement system yang dikembangkan oleh para penghobi dan profesional sebelum pembuatan Flutter. Dengan memanfaatkan struktur BLoc Flutter penelitian ini dilaksanakan untuk membuat aplikasi yang akan digunakan pada smartphone dengan sistem operasi Android dan iOS sebagai media pemesanan bagi PT. DLN dan Firebase Database sebagai Databasenya. Hasil uji aplikasi berjalan baik, setiap BLoC telah berhasil. Dan aplikasi tidak mengalami kendala yang besar. Uji BLoC Cubit dengan transaksi sukses dan gagal dapat berjalan dengan baik.

Unmanned vehicles (UAVs) are technological tools whose application is carried out in the civil and military areas for surveillance, recognition and intelligence tasks. Given its versatility and features, in this paper the implementation of an autopilot is determined, after an analysis of commercial models. Said device must comply with technical requirements for the automatic flight control of a medium-sized UAV, considering the operation scenarios in the northern border of Ecuador. In addition, the parameters that intervene in the control loops and the relevant simulations are specified. The results obtained from the experimental flights of the aircraft are reflected in graphs, where the stability of the plant properly calibrated for autonomous flight is verified.

The market of solar-powered Unmanned Aerial Vehicles (UAVs) for defence purposes and drone services is expected to grow by a factor of more than 2 in the next decade. From an aircraft design perspective, the main challenge is the scalability of the proposed architectures, which is needed to increase the payload capabilities. Beside some successful examples of wing-tail UAVs, some newcomers are developing prototypes with tandem-wing architectures, hence enlarging the possible design. The present paper aims to introduce a further step in this direction, taking also the box-wing architecture into account to show how the presence of wing tip joiners can provide benefits from the aeroelastic point of view. UAVs with take-off mass within 25 kg are considered and the main tools adopted are presented. These are an in-house developed Multi-Disciplinary Analysis and Optimization (MDAO) code called SD2020 and the open source aeroelastic code ASWING, both presented together with an assessment o...

In aerospace composite material design, it is common to encounter load bearing components that vary in thickness across their length. In plate design, ply drops, tow-steering, and the addition of stiffeners, all act to change both the section geometry and the effective stiffness of the part. Often, due to aerodynamic design constraints, the geometric profile must transition non-symmetrically, i.e. thickness is built up from a reference surface, meaning the mid-surface of the plate does not remain on a constant plane. These localised changes in geometry, and associated change of position of the mid-surface, lead to inherently three-dimensional states of stress. As a consequence, and especially for composite structures, there is the potential for significant through-thickness stresses and/or stress concentrations, leading to failure-for example debonding or delamination. By investigating the effects of geometric and effective stiffness changes, we are able to gain physical insight into structural behaviour in the regions of geometric transition. This is achieved through a parametric study, whereby we compare the behaviour as predicted by Classical Laminate Theory-a commonly utilised two-dimensional approach-with a finite element analysis based on the Unified Formulation by Carrera and co-workers. Based on these investigations, we are able to illustrate how rates of profile change and/or stiffness variation are linked to variance in the predicted location of the neutral plane of the two approaches which acts as a proxy measure for predicting through-thickness behaviour. Finally, we discuss the potential opportunity to utilise laminates that possess non-standard layups to tailor the load path through geometric transitions, thus offering a potential route for elastic tailoring that minimises undesirable through-thickness stresses.

This study aims to quantify and assess qualitatively the impact of modeling simplifications used to represent inertial and aerodynamic loads on the stresses and structural deformations of a centrifugal compressor in operation. The research object is the compressor of the high-pressure line of the DGEN 380 bypass turbine engine. Based on the virtual dynamometer WESTT CS/BV, the gas-dynamic parameters at the entrance to the centrifugal compressor and after the stage are determined. These values were used as initial parameters for numerical flow analysis. As part of the numerical strength analyses, a series of several load configurations were carried out: spin only, spin and inlet pressure normally applied on the working surface of the rotor blade, spin and outlet pressure normally applied on the working surface of the rotor blade, and one-way fluid-structure interaction analysis taking into account the aerodynamic loads with and without spinning. Based on the simulations, the level of similarity of a given load configuration with the last analysis, adopted as the reference, was determined. It was observed that in terms of the stress state, the rotational analysis taking into account the pressure on both sides of the blade gives satisfactory results, but the strain values are overestimated. The results obtained and the method of evaluation of compressor results can be used in research in the area of aviation, automotive, and refrigeration industries.

This study aims to quantify and assess qualitatively the impact of modeling simplifications used to represent inertial and aerodynamic loads on the stresses and structural deformations of a centrifugal compressor in operation. The research object is the compressor of the high-pressure line of the DGEN 380 bypass turbine engine. Based on the virtual dynamometer WESTT CS/BV, the gas-dynamic parameters at the entrance to the centrifugal compressor and after the stage are determined. These values were used as initial parameters for numerical flow analysis. As part of the numerical strength analyses, a series of several load configurations were carried out: spin only, spin and inlet pressure normally applied on the working surface of the rotor blade, spin and outlet pressure normally applied on the working surface of the rotor blade, and one-way fluid-structure interaction analysis taking into account the aerodynamic loads with and without spinning. Based on the simulations, the level of...

An analytic solution to the Riccati algebraic equation has been investigated by employing eigenvalue-eigenvector techniques combined with the Gram-Schmidt orthogonality process. An analytic solution to the Riccati algebraic equation has been investigated by employing eigenvalue-eigenvector techniques combined with the Gram-Schmidt orthogonalization process. The applied method is used to improve robust control of second and thirdorder state-dependent systems by handling nonlinearities. An H∞ controller is designed in this context via backstepping technique to enhance robustness and reduce computational effort. The effectiveness of this method has been demonstrated on a two-degree-of-freedom (2-DOF) robotic manipulator arm. Simulation results validate the performance of the controller, showing improved tracking accuracy, disturbance rejection, and overall system stability, thereby confirming the efficiency and applicability of the combined analytic Riccati algebraic equation and H∞ backstepping approach for nonlinear robotic systems.