cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.7509992
title: Numerical Study of Wall Ventilation in a Transonic Wind Tunnel

description: ABSTRACT: Transonic wind tunnels (TWT) are sophisticated tools for the investigations of flows with Mach numbers of order one. The most characteristic feature of a facility such as this is, for sure, the openings in the walls of the test section. The openings in the walls permit the proper relief effect, and this, on the other hand, makes possible the experimentation at the transonic range. The results to be presented in this paper correspond to an analysis of the flow in the test section of a TWT containing a NACA 0012 airfoil. Both numerical and experimental investigations were conducted. For the numerical investigation, a three-dimensional, finite-difference code, based on the diagonal algorithm, was employed, whereas for the experimentation, the classical static-pressure taps as well as the pressure sensitive paint (PSP) techniques were used. The classical static-pressure tap method is indicated as PSI technique. The pressure distributions were investigated for Mach numbers in the range of 0.6 - 0.8 and angles of attack from 0º up to 8º. The relief effect due to the slots, which provides for avoiding choking effects, is clearly demonstrated when one compares the flow along both solid and perforated walls. In the first part of this research report, the main focus will be on the numerical results. Notwithstanding this, and for comparison purposes, some experimental results will be called upon here, together with some literature data.
DOI: 10.6084/m9.figshare.7509992.v1
title: Numerical Study of Wall Ventilation in a Transonic Wind Tunnel

description: ABSTRACT: Transonic wind tunnels (TWT) are sophisticated tools for the investigations of flows with Mach numbers of order one. The most characteristic feature of a facility such as this is, for sure, the openings in the walls of the test section. The openings in the walls permit the proper relief effect, and this, on the other hand, makes possible the experimentation at the transonic range. The results to be presented in this paper correspond to an analysis of the flow in the test section of a TWT containing a NACA 0012 airfoil. Both numerical and experimental investigations were conducted. For the numerical investigation, a three-dimensional, finite-difference code, based on the diagonal algorithm, was employed, whereas for the experimentation, the classical static-pressure taps as well as the pressure sensitive paint (PSP) techniques were used. The classical static-pressure tap method is indicated as PSI technique. The pressure distributions were investigated for Mach numbers in the range of 0.6 - 0.8 and angles of attack from 0º up to 8º. The relief effect due to the slots, which provides for avoiding choking effects, is clearly demonstrated when one compares the flow along both solid and perforated walls. In the first part of this research report, the main focus will be on the numerical results. Notwithstanding this, and for comparison purposes, some experimental results will be called upon here, together with some literature data.
DOI: 10.6084/m9.figshare.7515296
title: Burning Rate Measurement of KNSu Propellant Obtained by Mechanical Press

description: ABSTRACT: The potassium nitrate (KNO3)/sucrose (C12H22O11) propellant, known as KNSu, is traditionally used in rocket studies by amateur groups. Performance tests of KNSu, whose composition is 65 wt% KNO3 and 35 wt% C12H22O11, cold-manufactured by mechanical press, are presented in this paper. The study determines the behaviour of density (ρ) and burning rate (r) as function of compression pressure (Pc) for the propellant grain manufacturing. Forty-four samples were prepared and tested, for seven different values of Pc. It was observed that ρ and r depend on Pc, according to quadratic polynomial functions, and the mass flux per unit area is a constant.
DOI: 10.6084/m9.figshare.7515296.v1
title: Burning Rate Measurement of KNSu Propellant Obtained by Mechanical Press

description: ABSTRACT: The potassium nitrate (KNO3)/sucrose (C12H22O11) propellant, known as KNSu, is traditionally used in rocket studies by amateur groups. Performance tests of KNSu, whose composition is 65 wt% KNO3 and 35 wt% C12H22O11, cold-manufactured by mechanical press, are presented in this paper. The study determines the behaviour of density (ρ) and burning rate (r) as function of compression pressure (Pc) for the propellant grain manufacturing. Forty-four samples were prepared and tested, for seven different values of Pc. It was observed that ρ and r depend on Pc, according to quadratic polynomial functions, and the mass flux per unit area is a constant.
DOI: 10.6084/m9.figshare.7508471
title: Modal Shape Analysis Using Thermal Imaging

description: ABSTRACT: In recent years, advances in aeronautical engineering field include, among others, the development of increasingly lightweight and flexible materials, allowing better performance of systems in applications such as Unmanned Aerial Vehicles, photographic model airplanes, light weight aircraft etc. This progress, however, can cause difficulties in design and various types of tests, such as those performed in modal analysis, since the instrumentation weight and shape can influence the behavior of very light and aerodynamic structures. This paper proposes a new technique to perform modal analysis in simple structures, eliminating the use of accelerometers, which must be numerous in this type of analysis and have significant weight; the whole structure can be analyzed at the same time, and this is an advantage in comparison with other techniques as vibrometer laser, that analyses one point at a time. The technique in question makes use of infrared imaging, detecting, through the heat, the structure deformation, allowing the trace of its modal shape. For this, a theoretical analysis and a thermomechanical modeling of a known structure are performed, with subsequent test to be validated, and finally the conclusions and suggestions for future work are presented.
DOI: 10.6084/m9.figshare.7508471.v1
title: Modal Shape Analysis Using Thermal Imaging

description: ABSTRACT: In recent years, advances in aeronautical engineering field include, among others, the development of increasingly lightweight and flexible materials, allowing better performance of systems in applications such as Unmanned Aerial Vehicles, photographic model airplanes, light weight aircraft etc. This progress, however, can cause difficulties in design and various types of tests, such as those performed in modal analysis, since the instrumentation weight and shape can influence the behavior of very light and aerodynamic structures. This paper proposes a new technique to perform modal analysis in simple structures, eliminating the use of accelerometers, which must be numerous in this type of analysis and have significant weight; the whole structure can be analyzed at the same time, and this is an advantage in comparison with other techniques as vibrometer laser, that analyses one point at a time. The technique in question makes use of infrared imaging, detecting, through the heat, the structure deformation, allowing the trace of its modal shape. For this, a theoretical analysis and a thermomechanical modeling of a known structure are performed, with subsequent test to be validated, and finally the conclusions and suggestions for future work are presented.
DOI: 10.6084/m9.figshare.7511120
title: A Six Degrees-of-Freedom Flight Dynamics Simulation Tool of Launch Vehicles

description: ABSTRACT: The use of digital simulation has become an essential activity during the development and operation of launch vehicles, due to the complexity of such systems. Of particular interest is the flight dynamics simulation, which investigates the behavior of the vehicle in flight subjected to forces and moments. This work presents a simulation tool suited to perform six degrees-of-freedom flight dynamics investigations of launch vehicles. Developed at the Instituto Nacional de Pesquisas Espaciais (INPE) and the Instituto de Aeronáutica e Espaço (IAE) in Brazil, the tool was implemented following the requirement for flexibility, so that it can be used to simulate different types of launch vehicles. The assessment of the vehicle performance and the vehicle payload capacity are some examples of analysis that can be performed with the tool. A modular programming strategy was employed to assure the tool flexibility. Therefore, the models presented in the tool were implemented as separate modules. The combination of these models can originate flight models of different launch vehicles. Two flight scenarios of Brazilian rockets were simulated and the results were verified against simulation tools already employed by aerospace community. The developed tool showed good agreement with respect to the simulators used to perform the comparison.
DOI: 10.6084/m9.figshare.7511120.v1
title: A Six Degrees-of-Freedom Flight Dynamics Simulation Tool of Launch Vehicles

description: ABSTRACT: The use of digital simulation has become an essential activity during the development and operation of launch vehicles, due to the complexity of such systems. Of particular interest is the flight dynamics simulation, which investigates the behavior of the vehicle in flight subjected to forces and moments. This work presents a simulation tool suited to perform six degrees-of-freedom flight dynamics investigations of launch vehicles. Developed at the Instituto Nacional de Pesquisas Espaciais (INPE) and the Instituto de Aeronáutica e Espaço (IAE) in Brazil, the tool was implemented following the requirement for flexibility, so that it can be used to simulate different types of launch vehicles. The assessment of the vehicle performance and the vehicle payload capacity are some examples of analysis that can be performed with the tool. A modular programming strategy was employed to assure the tool flexibility. Therefore, the models presented in the tool were implemented as separate modules. The combination of these models can originate flight models of different launch vehicles. Two flight scenarios of Brazilian rockets were simulated and the results were verified against simulation tools already employed by aerospace community. The developed tool showed good agreement with respect to the simulators used to perform the comparison.
DOI: 10.6084/m9.figshare.7507643
title: Method to Determine the Electrical Energy for Ignition of Electro-Explosive Devices

description: ABSTRACT: During field trials, it was observed that the delay of ignition of electro-explosive devices (EED) depends on ratings of power supplies or dynamo and also on the firing cable lengths. The change in ignition delay of EEDs due to altered supplied current will detoriate the repeatability of sequence of actions in time-critical armament applications. In order to study, supplement and analyze this observation, the measurement of electrical energy required for EEDs ignition is necessary. The electrical energy of EEDs has been determined experimentally by instrumentation and measurement setup using hall sensor and photo detector. The hall sensor is used to measure the actual current passing through EEDs when power supply is applied to them. Photo detector is used to detect the flash produced during EED ignition. By conducting repeated trials, it was observed that this method is reliable to determine the electrical energy required for EEDs ignition. With this parameter, the actual current to be supplied and the pulse width of supplied current for repeated ignition delays can be determined. Knowing the electrical energy of a particular EED by the proposed method, the required firing cable length and power supply for ignition of critical delay applications can be selected. This method also helps to design explosive-based ignition systems in defence applications.
DOI: 10.6084/m9.figshare.7507637
title: Functionalization of Multi-Walled Carbon Nanotube and Mechanical Property of Epoxy-Based Nanocomposite

description: ABSTRACT: The focus of this study is to evaluate the effect of carboxyl and amino functionalization of multiwalled carbon nanotubes on the mechanical property of the epoxy resin filled with modified carbon nanotubes. The carbon nanotubes were treated with sulfuric and nitric acids and also with hexamethylenediamine. The presence of acid and amine chemical groups on the carbon nanotube surface was confirmed by X-ray photoelectron spectroscopy. The composites were produced with epoxy resin and modified carbon nanotubes. Vickers hardness tests were carried out on the composites and neat resin. The results showed an increase of hardness in the composite prepared with functionalized carbon nanotubes. This phenomenon is due to the fact that the chemical interaction between modified carbon nanotube and epoxy resin is much stronger than between pristine carbon nanotube and epoxy resin. This stronger interaction is related to the presence of functionalized carbon nanotubes.
DOI: 10.6084/m9.figshare.7507637.v1
title: Functionalization of Multi-Walled Carbon Nanotube and Mechanical Property of Epoxy-Based Nanocomposite

description: ABSTRACT: The focus of this study is to evaluate the effect of carboxyl and amino functionalization of multiwalled carbon nanotubes on the mechanical property of the epoxy resin filled with modified carbon nanotubes. The carbon nanotubes were treated with sulfuric and nitric acids and also with hexamethylenediamine. The presence of acid and amine chemical groups on the carbon nanotube surface was confirmed by X-ray photoelectron spectroscopy. The composites were produced with epoxy resin and modified carbon nanotubes. Vickers hardness tests were carried out on the composites and neat resin. The results showed an increase of hardness in the composite prepared with functionalized carbon nanotubes. This phenomenon is due to the fact that the chemical interaction between modified carbon nanotube and epoxy resin is much stronger than between pristine carbon nanotube and epoxy resin. This stronger interaction is related to the presence of functionalized carbon nanotubes.
DOI: 10.6084/m9.figshare.7507643.v1
title: Method to Determine the Electrical Energy for Ignition of Electro-Explosive Devices

description: ABSTRACT: During field trials, it was observed that the delay of ignition of electro-explosive devices (EED) depends on ratings of power supplies or dynamo and also on the firing cable lengths. The change in ignition delay of EEDs due to altered supplied current will detoriate the repeatability of sequence of actions in time-critical armament applications. In order to study, supplement and analyze this observation, the measurement of electrical energy required for EEDs ignition is necessary. The electrical energy of EEDs has been determined experimentally by instrumentation and measurement setup using hall sensor and photo detector. The hall sensor is used to measure the actual current passing through EEDs when power supply is applied to them. Photo detector is used to detect the flash produced during EED ignition. By conducting repeated trials, it was observed that this method is reliable to determine the electrical energy required for EEDs ignition. With this parameter, the actual current to be supplied and the pulse width of supplied current for repeated ignition delays can be determined. Knowing the electrical energy of a particular EED by the proposed method, the required firing cable length and power supply for ignition of critical delay applications can be selected. This method also helps to design explosive-based ignition systems in defence applications.
DOI: 10.6084/m9.figshare.7514441
title: Electromechanical Impedance - Based Structural Health Monitoring Instrumentation System Applied to Aircraft Structures and Employing a Multiplexed Sensor Array

description: ABSTRACT: The electromechanical impedance method has been seen as a promising tool for structural health monitoring regarding different types of structures and purposes. Most importantly, this method can be used in real-time applications. Frequently, massive, high-cost, single-channel impedance analyzers are used to process the time domain data, aiming at obtaining the complex, frequency-dependent electromechanical impedance functions and therefore infer about the presence, position and extent of an existing damage. However, for large structures, it is desirable to deploy an array of piezoelectric transducers over the area to be monitored and interrogate these transducers successively, in order to increase the probability of successful detection of damage at an early phase. The literature describes many miniaturized systems that can monitor large structures, however, presenting serious restrictions on data acquisition capabilities. This paper presents a hardware that is not limited to any data acquisition restriction, exhibiting an innovative way to measure the electromechanical impedance of multiplexed bonded transducers. Each logical block of the proposed architecture is presented in detail. The proposed system not only avoids costly fast Fourier transform analyzers/ algorithms, but also evades high-speed data acquisition hardware. A prototype using inexpensive integrated circuits and a digital signal processor was built and tested for two different types of structures: an aluminum beam and an aircraft aluminum panel. Simulated damages were introduced to each structure, and the detection performance of the prototype was tested. The actual prototype uses a universal serial bus connection to communicate with a personal computer.
DOI: 10.6084/m9.figshare.7514441.v1
title: Electromechanical Impedance - Based Structural Health Monitoring Instrumentation System Applied to Aircraft Structures and Employing a Multiplexed Sensor Array

description: ABSTRACT: The electromechanical impedance method has been seen as a promising tool for structural health monitoring regarding different types of structures and purposes. Most importantly, this method can be used in real-time applications. Frequently, massive, high-cost, single-channel impedance analyzers are used to process the time domain data, aiming at obtaining the complex, frequency-dependent electromechanical impedance functions and therefore infer about the presence, position and extent of an existing damage. However, for large structures, it is desirable to deploy an array of piezoelectric transducers over the area to be monitored and interrogate these transducers successively, in order to increase the probability of successful detection of damage at an early phase. The literature describes many miniaturized systems that can monitor large structures, however, presenting serious restrictions on data acquisition capabilities. This paper presents a hardware that is not limited to any data acquisition restriction, exhibiting an innovative way to measure the electromechanical impedance of multiplexed bonded transducers. Each logical block of the proposed architecture is presented in detail. The proposed system not only avoids costly fast Fourier transform analyzers/ algorithms, but also evades high-speed data acquisition hardware. A prototype using inexpensive integrated circuits and a digital signal processor was built and tested for two different types of structures: an aluminum beam and an aircraft aluminum panel. Simulated damages were introduced to each structure, and the detection performance of the prototype was tested. The actual prototype uses a universal serial bus connection to communicate with a personal computer.
DOI: 10.6084/m9.figshare.7516136
title: A Computational Modeling for Semi-Coupled Multiphase Flow in Atmospheric Icing Conditions

description: ABSTRACT: A two-dimensional second-order positivity-preserving finite volume upwind scheme is developed for a semi-coupled algorithm involving the air and droplet flow fields in the Eulerian frame, which shares the grid for each phase. Special emphasis is placed on the computational modeling, which is induced from a strongly-coupled algorithm that satisfies the strict hyperbolicity and its numerical scheme based on the Harten-Lax-van Leer-Contact solver preserving the positivity to handle multiphase flow in the Eulerian frame. The proposed modeling associated with the semi-coupled algorithm including the Navier-Stokes and droplet equations takes into account different boundary conditions on the solid surface for each phase. The verification and validation studies show that the new scheme can solve the air and droplet flow fields in fairly good agreement with the exact analytical solutions and experimental data. In particular, it accurately predicted the maximum value of the droplet impingement intensity near the stagnation region and the droplet impingement area.
DOI: 10.6084/m9.figshare.7516136.v1
title: A Computational Modeling for Semi-Coupled Multiphase Flow in Atmospheric Icing Conditions

description: ABSTRACT: A two-dimensional second-order positivity-preserving finite volume upwind scheme is developed for a semi-coupled algorithm involving the air and droplet flow fields in the Eulerian frame, which shares the grid for each phase. Special emphasis is placed on the computational modeling, which is induced from a strongly-coupled algorithm that satisfies the strict hyperbolicity and its numerical scheme based on the Harten-Lax-van Leer-Contact solver preserving the positivity to handle multiphase flow in the Eulerian frame. The proposed modeling associated with the semi-coupled algorithm including the Navier-Stokes and droplet equations takes into account different boundary conditions on the solid surface for each phase. The verification and validation studies show that the new scheme can solve the air and droplet flow fields in fairly good agreement with the exact analytical solutions and experimental data. In particular, it accurately predicted the maximum value of the droplet impingement intensity near the stagnation region and the droplet impingement area.
DOI: 10.6084/m9.figshare.7509242
title: Interannual Variability of Precipitation for the Centro de Lançamento de Alcântara in ENSO-Neutral Years

description: ABSTRACT: The interannual variability of precipitation in El Niño/Southern Oscillation-neutral years was studied for the Centro de Lançamento de Alcântara region. Monthly precipitation, sea surface temperature, wind at 925 hPa and outgoing longwave radiation data from various gridded datasets for the 1951-2010 period (60 years) were used. The data grouping was based on terciles. For the Centro de Lançamento de Alcântara in El Niño/Southern Oscillation-neutral years, March is the month of the rainy quarter (March to May) when the interhemispheric gradient of the sea surface temperature anomalies over the Atlantic (GRAD) and the atmospheric circulation at 925 hPa over the Centro de Lançamento de Alcântara were able to best explain the variability of precipitation. In this month, the wind direction at 925 hPa was the factor that explained the highest fraction of precipitation variance (40%), followed by GRAD (30%) and the wind magnitude (20%). For the Centro de Lançamento de Alcântara, in general, above-average precipitation was related to weak north-northeasterly low-level winds and southward GRAD, while below-average precipitation was related to strong east-northeasterly low-level winds and northward GRAD. These features were related to an eastward expansion of the Amazon convection towards the northern Northeast Brazil and might be related to a slight southward displacement of the Intertropical Convergence Zone in above-average precipitation years.