ENCIT2012-148 STABILITY AND CONTROL OF AN UNMANNED AERIAL VEHICLE FOR AERIAL PHOTOGRAPHY USING ANALYTICAL AND NUMERICAL METHODS - PDF
Welberth Douglas Nascimento, Manuel Nascimento Júnior, UnB, Brazil
Abstract: This current work aims at analyzing the stability and control of a short range unmanned aerial vehicle (UAV) with an imaging system. The vortex lattice method and the lifting line theory will be applied in order to estimate aerodynamic characteristics of the airplane. Data in trimmed flight will be obtained by means of simulations using the vortex lattice method; and the dynamic model of the airplane will be built based on results from these simulations.
Keywords:Stability; Control; UAV.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-002 SIMULATION OF ABLATION WITH TWO MOVING FRONTS IN A ROCKET TPS VIA AN INTERFACE TRACKING METHOD - PDF
Humberto Araujo Machado, IAE, Brazil
Abstract: Space and sub-orbital vehicles reach high velocities within atmosphere, about 100 km over Earth's surface. Such high velocities result in aerodynamic heating and air temperature surpasses 2000o C at the stagnation point. Besides the effects of high temperatures on the mechanical behavior of the structure and on-board devices, it is mandatory to preserve the payload, by using an efficient TPS (Thermal Protection System). Along the years ablative materials have been effectively used as TPS of space vehicles. In order to obtain the temperature profile and the heat load, the energy conservation equation has to be solved, along the moving boundary problem concerned to the ablation process. The coupling between the heat transfer processes in the surface and within the layers represent an additional difficult. A common approach is to consider the heat conduction as one-dimensional, in the normal direction relative to the local surface. However, such hypothesis becomes inaccurate as temperature gradients in the tangential direction, change of material or a great thickness variation occur. In this work, the computational simulation of the ablative process in the vicinity of the stagnation point during the flight of VSB-30 sounding rocket via an interface tracking method is presented, taking into account the effects of the two-dimensional conduction in the wall layers. The ablative model considers the presence of two simultaneous moving fronts, the pyroyisis and char fronts. Such procedure will allow a more accurate dimensioning of the TPS, contributing for project optimization.
Keywords:Simulation; Ablation; Moving boundary; TPS; Aerodynamic heating.
Presentation Schedule: Tuesday, 17:40-18:00. Session: AES3-2/AES2. Presenter: Humberto Araujo Machado.
ENCIT2012-099 MATHEMATICAL MODELING OF THE CTS - CAPTIVE TRAJECTORY SYSTEM - PDF
Guido Pires Arantes Ubertini, João Batista Pessoa Falcão Filho, IAE, Brazil
Abstract: The TTP (Pilot Transonic Wind Tunnel of IAE - Aeronautics and Space Institute) is a modern tunnel capable of aerodynamic tests in Mach number range from 0.2 to 1.3 with automatic controls of pressure (from 0.5 bar to 1.2 bar), temperature and humidity. In a transonic wind tunnel design the test section walls are semi-open to allow mass flow extraction, which is important to prevent aerodynamic chocking phenomenon, minimize shock/expansion wave reflections from walls, and also to help on wall effects correction. To set the mass flow ratio through the walls, the test section is enveloped by a plenum chamber, in which the pressure is controlled by means of a dedicated compressor. What determines how much of the flow will pass through the walls are mainly the plenum chamber pressure and the reentry flaps positioning, located at the end of the test section. On high speed tunnels, simple aerodynamic models are connected through a device named sting wich supports the model by its back, in order to reduce as much as possible the interference effects with the clamping devices. However, there are more complex models composed of more than one body, such as aerospace vehicles with boosters coupled to a central body or artifacts suspended in aircraft wings, wich cannot be correctly positioned in the test section without an auxiliary positioning device. A positioner system of three degrees of freedom called CTS (Captive Trajectory System) was designed in order to simulate a missile being jettisoned from a generic fuselage, expanding the ability of tests to be developed in the TTP. This positioner controls the position in the X and Y axis of the projectile and its angle of attack \&\#945; through the linear displacement of three independent movers, controlled by step motors. The correct positioning of these three movers is required for the aerodynamic model fixed to the device to be placed in the desired position and attitude. This work demonstrates step by step the mathematical modeling performed for the device, and the equations that relate the position and attitude of the aerodynamic model with the position of the movers of the CTS positioning system designed for the TTP.
Keywords:Captive Trajectory System; Mathematical Modeling; Positioning; Attitude.
Presentation Schedule: Tuesday, 14:20-14:40. Session: AES3-1. Presenter: Guido Pires Arantes Ubertini.
ENCIT2012-100 CONTROL SYSTEM OF THE CTS - CAPTIVE TRAJECTORY SYSTEM - PDF
Guido Pires Arantes Ubertini, João Batista Pessoa Falcão Filho, IAE, Brazil
Abstract: The TTP (Pilot Transonic Wind Tunnel of IAE - Aeronautics and Space Institute) is a modern tunnel capable of aerodynamic tests in Mach number range from 0.2 to 1.3 with automatic controls of pressure (from 0.5 bar to 1.2 bar), temperature and humidity. In a transonic wind tunnel design the test section walls are semi-open to allow mass flow extraction, which is important to prevent aerodynamic chocking phenomenon, minimize shock/expansion wave reflections from walls, and also to help on wall effects correction. To set the mass flow ratio through the walls, the test section is enveloped by a plenum chamber, in which the pressure is controlled by means of a dedicated compressor. What determines how much of the flow will pass through the walls are mainly the plenum chamber pressure and the reentry flaps positioning, located at the end of the test section. On high speed tunnels, simple aerodynamic models are connected through a device named sting wich supports the model by its back, in order to reduce as much as possible the interference effects with the clamping devices. However, there are more complex models composed of more than one body, such as aerospace vehicles with boosters coupled to a central body or artifacts suspended in aircraft wings, wich cannot be correctly positioned in the test section without an auxiliary positioning device. A positioner system of three degrees of freedom called CTS (Captive Trajectory System) was designed in order to simulate a missile being jettisoned from a generic fuselage, expanding the ability of tests to be developed in the TTP. This positioner controls the position in the X and Y axis of the projectile and its angle of attack \&\#945; through the linear displacement of three independent movers, controlled by step motors. The controller will guide the device from TTP's control room using a software created in LabView 2009 platform. This software will calculate the necessary moves on the device to place the aerodynamic model in the desired position. These informations will be sent to the microcontroler, wich is responsible for correctly driving the step motors. The microcontroler will then send signs to the drivers that control each step motor. This work describes details of each one of the three steps of the control system of the Pilot Transonic Wind Tunnel's Captive Trajectory System.
Keywords:Captive Trajectory System; Control System; Positioning; Attitude.
Presentation Schedule: Tuesday, 15:40-16:00. Session: AES3-1. Presenter: Guido Pires Arantes Ubertini.
ENCIT2012-128 PRELIMINARY DESIGN OF THE EXHAUST MANIFOLD FOR THE 14-X HYPERSONIC AEROSPACE VEHICLE. - PDF
Bruno Ferreira Porto, Paulo Gilberto de Paula Toro, IEAv, Brazil
Abstract: The purpose of this paper is present the preliminary design of an exhaust manifold to diverge the supersonic flow of the hypersonic experiment of the 14-X aerospace hypersonic flight experiment.
Keywords:hypersonic; scramjet; exhaust manifold; 14-X.
Presentation Schedule: Tuesday, 15:20-15:40. Session: AES3-1. Presenter: Valeria S. Faillace O. Leite.
ENCIT2012-233 FLOW AND ACOUSTIC NOISE OF SINGLE STREAM SUBSONIC JETS FROM NOZZLES WITH AND WITHOUT CHEVRONS - PDF
Rafael Costa Engel, Cesar J. Deschamps, UFSC, Brazil
Carlos R. I. Silva, EMBRAER, Brazil
Abstract: Numerical predictions of the flow field and acoustic noise of jets from nozzles with and without chevrons have been obtained for Mach number M=0.9 and Reynolds number Re=1.38 x 106. The fluid flow simulations were based on two turbulence models, a Reynolds stress transport model (RSTM) and a cubic k-epsilon model. A hybrid approach was adopted for noise prediction, with turbulence statistics, such as length and time scales, being obtained from the fluid flow solution and used as input for two methods of noise prediction: the wavepro1 method available in the code CAA++ and the Lighthill Ray-Tracing (LRT) method developed by Silva et al. (2011). Both methods are based on the Lighthill´s acoustic analogy, but differ from each other in the way noise source terms are evaluated and sound pressure waves are propagated to the far-field. It has been verified that only the LRT method is capable of providing predictions for the noise spectra at the far field in close agreement with experimental data.
Keywords:Chevron Nozzle; Aeroacoustics; Jet Noise.
Presentation Schedule: Tuesday, 14:40-15:00. Session: AES3-1. Presenter: Cesar J. Deschamps.
ENCIT2012-316 EVALUATION OF A VITIATED AIR GENERATOR FLOW CONDITIONS FOR THE 14-X HYPERSONIC VEHICLE COMBUSTOR TESTS - PDF
Fábio Henrique Eugênio Ribeiro, Valéria Serrano Faillace Oliveira Leite, IEAv, Brazil
Abstract: To study the supersonic combustion physical phenomena it is required ground test facilities such as shock tunnels, shock tubes and vitiated air generators. For this purpose, a direct-connected supersonic combustion research facility is now being assembled at the Institute for Advanced Studies (IEAv/DCTA). This facility was first mounted at the Combustion and Propulsion Laboratory (LCP/INPE) and last year was transfered to the IEAv, in order to help the research of the supersonic combustion inside the combustor of the X-14 hypersonic vehicle, that is being developed at this Institute. The direct-connected supersonic combustion test bench consists basically of a vitiated air generator (VAG) unit and a nozzle directly coupled to the supersonic combustor to be tested. The flow at the exit of the test facility simulates the air conditions behind the oblique or conical shock waves formed ahead of vehicles flying at hypersonic speeds. These are the same conditions at a scramjet (supersonic combustion ramjet) combustor entrance and it is a high temperature supersonic flow. To simulate this flow on the test facility, oxygen enriched air is heated by combustion inside the VAG and then accelerated through the nozzle, generating the "vitiated air" containing the desired flow properties plus the heating process combustion products, while keeping the same atmospheric oxygen content. In order to control and adjust the flow test conditions at the facility exhaust, for the new values, i. e., for the conditions inside de X-14 combustor, an evaluation of the flow inside the entire facility should be done to find the new equivalence ratio of the reactants (used to heat the air), and the new shape of the nozzle to reach the desireble Mach number (the one inside the combustor) at the exit of the test bench. This work presents details of the study of the entire flow inside the facility where the combustion process in the vitiated air generator is analyzed, using the software CHEMKIN-IIIâ, and the flow inside the nozzle is evaluated, using the Jameson scheme, which is a finite volume discretization method with artificial dissipative terms, for the solution of the Euler equations, considering two gas models: a calorically perfect and a frozen one. This study allows us to adjust and control the test flow conditions, at nozzle exit, to adapt the ground test facility to the research of the supersonic combustion inside the 14-X combustor.
Keywords:vitiated air generator; transonic nozzle; ground test facility; reactive flow.
Presentation Schedule: Tuesday, 15:00-15:20. Session: AES3-1. Presenter: Fábio Henrique Eugênio Ribeiro.
ENCIT2012-103 ACCURACY ASSESSMENT OF THE SPECTRAL DIFFERENCE SCHEME FOR CONSERVATION LAWS - PDF
Carlos Breviglieri Junior, ITA, Brazil
Fabio Mallaco Moreira, Unicamp, Brazil
João Luiz Filgueiras de Azevedo, IAE, Brazil
Abstract: The Spectral Difference method is designed to support high-order accuracy on unstructured grids. It uses a domain transformation formulation that eases the implementation while improving computational efficiency. The authors investigate various solution and flux point distributions of different orders of accuracy for model problems. The method is found to achieve the expected order of accuracy and its one-dimensional reconstruction procedure will be used for 2-D simulations on the final paper as reported here.
Keywords:High-Order; Spectral Difference; Unstructured Meshes; CFD.
Presentation Schedule: Tuesday, 18:20-18:40. Session: FMR4-3. Presenter: Carlos Breviglieri.
ENCIT2012-041 STUDY OF CONSERVATION ON IMPLICIT TECHNIQUES FOR UNSTRUCTURED FINITE VOLUME NAVIER-STOKES SOLVERS - PDF
Carlos Alberto Junqueira Branco Junior, ITA, Brazil
Leonardo C. Scalabrin, EMBRAER, Brazil
Edson Basso, João Luiz Filgueiras de Azevedo, IAE, Brazil
Abstract: The work is an study of conservation on linearization techniques of implicit time-marching schemes for unstructured finite volume Reynolds averaged Navier-Stokes formulation. The numerical flux is calculated using an upwind discretization based on the flux vector splitting. This numerical treatment results in a very large sparse linear system. The solution of this full implicit linear system is very expensive in the context of computational resources, and in most of cases impractical. Numerical approaches are commonly used by the scientific community to treat sparse linear systems, such as the point-implicit integration, which is a very popular time-marching method used by some prestigious and recognized commercial solvers. However, numerical approaches to solve implicit linear systems can be non conservative in time, even for formulations which are conservative by construction, as the finite volume techniques. Moreover, there are physical problems which strongly demand conservative schemes in order to achieve the correct numerical solution. The work discusses numerical requirements to avoid such issue and proposes solutions to achieve a conservative integration method.
Keywords:Computational Fluid Dynamics; Time Marching Methods; Flux Vector Splitting Scheme; Conservative Discretization.
Presentation Schedule: Monday, 18:40-19:00. Session: FMR4-2. Presenter: Carlos Junqueira Junior.
ENCIT2012-251 STRUCTURAL DESIGN OF MINI-UAVS WITH CONVENTIONAL AND ALTERNATIVE MATERIALS - PDF
Zeus Siqueira Bessoni, Manuel Nascimento Dias Barcelos Júnior, UnB, Brazil
Abstract: The goal of this paper is to present the structural design of an unmanned aerial vehicle (UAV) using conventional and unconventional materials from the aerospace industry. In order to design each component of the aircraft as optimized and light as possible, a methodology based on analytical, numerical and experimental analyses will be developed. The aircraft design was devised according to the requirements for monitoring UAVs to be as optimized as possible taking into account every detail in design areas such as aerodynamics, structures, stability and performance. The work seeks to structure a methodology to create a product to be equipped with optical cameras and / or infrared and systems for navigation, control, positioning and real time data storage and transmission. The main application areas for the project are supervision, tracking and recognition. The aircraft can be employed to different kind of missions by the public sector such as soldiers, police officers, firefighters and by the private sector in general.
Keywords:Aircraft; UAV; unconventional materials; conventional materials; analytical analyses; numerical analyses; experimental analyses.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-048 DESIGN OF THE BRAZILIAN 14-X HYPERSONIC AEROSPACE VEHICLE - PDF
Felipe J. Costa, Paulo Gilberto de Paula Toro, Tiago C. Rolim, Giannino P. Camillo, Roberto C. Follador, Marco A. S. Minucci, IEAv, Brazil
Viliam Sinka, FATEC, Brazil
Abstract: A new generation of scientific aerospace vehicles, using advanced hypersonic air-breathing propulsion based on supersonic combustion "scramjet" technology, is in development at several research centers. This new propulsion system (scramjets) is economically and ecologically more attractive than the conventional rocket propulsion. The Brazilian 14-X Hypersonic Aerospace Vehicle, designed at the Prof. Henry T. Nagamatsu Laboratory of Aerothermodynamics and Hypersonics, at the Institute for Advanced Studies (IEAv), is a technological demonstrator using:i) "waverider" technology to provide lift to the aerospace vehicle, and ii) "scramjet" technologyto provide hypersonic airbreathing propulsion system based on supersonic combustion. Pure waverider aerodynamic as well as scramjet power off have been experimentally investigated at the T3 0.60-m. nozzle exit diameter Reflected Hypersonic Shock Tunnel, funded by The State of São Paulo Research Foundation (FAPESP). Pressure measurements at pure waverider external upper and lower surfaces and scramjet power off on internal surfaces provide wind-tunnel data to design the full 2-m. long 14-X Hypersonic waverider scramjet Mach number 10 Aerospace Vehicle to atmospheric flight at 30km altitude.
Keywords:14-X Hypersonic Aerospace Vehicle; waverider; Hypersonic Airbreathing Propulsion; scramjet.
Presentation Schedule: Tuesday, 16:20-16:40. Session: AES3-1. Presenter: Valeria S. Faillace O. Leite.
ENCIT2012-342 CONJUGATED HEAT TRANSFER MODELS FOR HEATED AERONAUTICAL PITOT TUBES: EXPERIMENTAL VALIDATION WITH A4 SKYHAWK FLIGHT TESTS - PDF
José Roberto Brito de Souza, Kleber Marques Lisboa, Ivana Gabriela dos Santos Cerqueira, Carolina Palma Naveira-Cotta, Renato Machado Cotta, UFRJ, Brazil
José Luiz Zanon Zotin, INMETRO, Brazil
Abstract: The purpose of this work is to study both theoretically and experimentally the conjugated heat transfer problem associated with the transient thermal behavior of a heated aeronautical Pitot tube, from the aircraft A4 Skyhawk of the Brazilian Navy. The aim is to demonstrate the importance of accounting for the conduction-convection conjugation in more complex models that attempt to predict the icing of such sensors under critical atmospheric conditions. The experimental analysis involves the use of thermocouples fixed to the surface of the Pitot tube and temperature measurements acquired by a data logger installed in the frontal cone of the airplane. The theoretical analysis involves the proposition of an improved lumped-differential model for heat conduction along the probe, approximating the transversal temperature gradients within the solid. The flow and heat transfer problem in the fluid is solved using the boundary layer equations for compressible flow, applying the Illingsworth variables transformation considering a locally similar flow. The nonlinear partial differential equations are solved using the Generalized Integral Transform Technique (GITT) in the Mathematica v7.0 platform.
Keywords:conjugated problem; compressible flow; convection; lumped analysis; Pitot tube; boundary layer equations.
Presentation Schedule: Tuesday, 16:00-16:20. Session: AES3-1. Presenter: Kleber Marques Lisboa.