GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING
Most widely held works by GEORGIA INST OF TECH ATLANTA SCHOOL OF AEROSPACE ENGINEERING
Audible and Ultrasonic Acoustic Emissions from Composite Solid Propellants ( Book )
4 editions published between 1975 and 1977 in English and held by 1 library worldwide
An apparatus to test the audible and ultrasonic emissions from composite solid propellants was designed, constructed and checked out. Tests were conducted at 300 psia for eight aluminized HTPB-AP propellants. The tests were conducted under both nitrogen and air pressurization. For the audible emissions in the range 100 - 2500 Hz there is a marked effect of the pressurization fluid. In air the noise output is 10,000 higher than in nitrogen. There is a definite possibility that the noise output is responsible for observed chamber pressure roughness level. For the ultrasonic signal in the range 50 to 300 kHz there are strong spectral peaks observed but their origin is not clear and they do not correlate with observed deflagration behavior. For audible signals a striking effect of AFCAM aluminum coating is the reduction of signal strength.
Solid Propellant Admittance Measurements by the Driven Tube Method ( Book )
4 editions published between 1974 and 1977 in English and held by 1 library worldwide
The progress made during the fourth year of an investigation for the measurement of the response of a burning solid propellant to flow disturbances is presented. In this study a modification of the impedance tube technique is used to measure the response over a wide frequency range. Further refinements in the data reduction computer program are discussed. Anomalous behavior for high pressure (300 psig) tests which shows that the propellant sample periodically drives and damps acoustic oscillations during a burn was resolved. Techniques for improving the accuracy of the measured data and the quality of the burn have been developed. Testing will resume during the next year. (Author).
Integrated Reconfigurable Intelligent Systems (IRIS) for Complex Naval Systems ( Book )
3 editions published between 2009 and 2011 in English and held by 1 library worldwide
The report details the research work has been done by the Aerospace Systems Design Laboratory (ASDL) in developing and applying the Integrated Reconfigurable Intelligent Systems (IRIS) concept for the period of February 22 to June 30, 2009. The main objective of the work for this period is to further develop and refine the integrated modeling and simulation environment in order to investigate the behavior of complex naval systems for improving the ship design and operations. Five individual tasks were conducted to fulfill this objective. Models revised based on the notional YP were integrated and tested; a control architecture with inference engine was proposed and evaluated based on defined scenarios; comparison of plain NN models and NN models with the block-structure was performed for evaluating accuracy of the surrogate models; a suitable framework and a database engine has been selected to facilitate the information management for developing the HMI of the simulation environment; a robust and a resilient approaches were proposed to conduct design space exploration in order to obtain an ultimate design with increased survivability and mission effectiveness. The rest of the report will explain the accomplishments for each task in details.
Controlling Mechanisms of Pulsating Incineration Processes ( Book )
3 editions published between 1994 and 1996 in English and held by 1 library worldwide
The goal of this study is to investigate the fundamental processes that control the performance of acoustically excited incineration systems. Cold flow tests performed under the first year of this program have demonstrated that natural acoustic mode oscillations, in the absence of net flow into or out of the volume, can be used to promote rapid mixing. Increased acoustic pressure amplitudes in the chamber were shown to increase the mixing rates. The dependence of the mixing rate on the mode of acoustic excitation was shown to be highly complex. Acoustic streaming also appears to have a significant influence upon flow and mixing patterns in the simulated incinerator. The effect of acoustic oscillations upon waste incineration was investigated by studying the effect of acoustic oscillations upon dry ice sublimation. This study showed that the presence of pulsations enhanced the sublimation process, which strongly suggests that they would also enhance the process of burning solid wastes. Preparations are underway to investigate the effects of acoustics on the combustion of waste surrogates.
Numerical Solution of Three-Dimensional Unsteady Viscous Flows ( Book )
3 editions published between 1991 and 1992 in English and held by 1 library worldwide
The behavior of free shear layers within ramjet dump combustors is studied through the numerical solution of unsteady compressible Navier-Stokes equations. Three configurations are considered: (a) a short combustor with an open downstream boundary, (b) a long combustor with an open downstream boundary, and (c) a short combustor with a partially blocked downstream boundary. Vorticity contours of the computed flow fields in all the three cases reveal oscillations of the shear layer, roll up and shedding of organized vortices. A Fourier analysis of the computed flow fields indicates that the natural acoustic frequency of the system, and the natural shear layer instability frequency are the two dominant frequencies of the flow field. It is also observed that the boundary conditions play a crucial role in the behavior of the combustor flow field.
Investigation of the Flame-Acoustic Wave Interaction during Axial Solid Rocket Instabilities ( Book )
3 editions published between 1985 and 1991 in English and held by 1 library worldwide
The primary objective of this study is the determination of the fundamental mechanisms responsible for the driving of axial instabilities by solid propellant flames. During the report period, the behavior of a premixed flame stabilized on the side wall of a duct in the presence of an axial acoustic field was investigated both theoretically and experimentally. The developed model solutions show that driving occurs due to the combustion process heat addition while outside the reaction zone the waves are damped by viscous processes. This damping increases as the thickness of the acoustic boundary layer increases. Experimental facilities for studying oscillating duct flow sin the presence and absence of flames were developed. Cold flow studies verified the presence of an excess velocity region within the acoustic boundary layer (i.e., the Richardson Effect) and the dependence of the boundary layer thickness upon the frequency and wall injection velocity. Reactive flow studies showed that the behavior of the flame depends upon its location relative to the standing acoustic wave. When the flame was positioned next to a velocity antinode, unexpected instabilities appeared on its surface eventually resulting in severe flame distortion. Also, the measured C-C and C-H radiation signals were periodic and they oscillated with the same frequency as the acoustic wave. Keywords: Flame-Acoustic interactions; and Flame driving.
Combustion Generated Noise in Turbopropulsion Systems ( Book )
3 editions published between 1973 and 1975 in English and held by 1 library worldwide
Experiments on noise radiation by open turbulent premixed flames are described. Detailed directionality distributions, scaling rules for acoustic power radiated, thermo-acoustic efficiency and spectral content are presented and discussed. Scaling rules for reacting volume are generated by a direct flame photography technique. These experiments are shown to be quite useful in decomposing combustion noise scaling laws. The acoustic power is shown to scale as U(2.7) D(2.8) SL(1.4) F(0.4), and combustion noise spectra peak in the 250-700 Hz range. The directionality is quite weak for noise from open turbulent flames. The experimental results are critically examined in the light of the theoretical predictions from Strahle's theory of combustion noise. (Author).
Noise Suppression in Jet Inlets ( Book )
3 editions published between 1978 and 1980 in English and held by 1 library worldwide
This research program was concerned with the development of an analytical technique, based on an integral representation of the external solutions of the Helmholtz equation, for the prediction of the sound radiated from complicated, acoustically lined, axisymmetric bodies having complex sound sources. The purpose of this research program was to generate efficient computer codes for the prediction of the sound radiated from acoustically lined jet engine inlets. In the experimental tests two geometrical configurations were studied, a straight duct and a jet engine inlet. Both of these configurations were tested with hard walls and the straight duct was tested with an acoustic liner consisting of a matrix of Helmholtz resonators. It was found that very good agreement was obtained for the hard walled configurations while there were some discrepancies with the lined wall case. It is conjectured that this discrepancy in some of the lined wall results is mainly due to the particular liner theory used to calculate the effective admittance of the liner.
Rocket Research at Georgia Tech ( Book )
3 editions published between 1979 and 1981 in English and held by 1 library worldwide
Task I. During the reporting period, the impedance tube setup was utilized in the determination of the admittances ot two aluminized solid propellants. Both the pressure coupled response and the gas phase losses have been determined over the frequency range of 400-1200 Hertz. In a separate study, the feasibility of utilizing either quartz or piezoceramic crystals in the direct measurement of the mass loss of burning solid propellants has been investigated. Finally studies aimed at the adaptation of the impedance tube setup for the measurement of the simulating heating values for practical propellants, have been started. Task II. Studies were continued on burning in and around the near wake of an axisymmetric model at Mach 3. Burning tests with radiant and axial injection of pure hydrogen have been completed. Burning tests with axial injection of diluted hydrogen, velocity coupled response of burning solid propellant has been initiated. Task III. Further studies were made of aluminum accumulation and agglomeration on the propellant burning surface and droplet combustion in the gas flow from the surface. Modification of the aluminum powder to control agglomeretion were evaluated by propellant combustion studies and found to be highly effective. Task IV. Experimental and analytical studies were continued on the subject of turbulence-induced pressure flucuations in a rocket-like cavity. An advanced theory has provided closure between theory and experiment on one experimental facility. A fuel rocket motor simulator was built and preliminary results were attained to show the separation between propagational sound and local hydrodynamic noise.
Combustion Mechanisms of Solid Propellants ( Book )
3 editions published between 1980 and 1993 in English and held by 1 library worldwide
A summary report is made of research on the latter phases of this contract, involving mechanisms of propellant combustion. In eight sections, work on the following is reported: (1) Status of understanding; (2) Decomposition of binders as revealed by hot stage microscope studies; (3) Systematic studies of combustion of 'sandwiches' of binder laminae between ammonium perchlorate laminae, with particular emphasis on quench-burning of thin-binder sandwiches; (4) Exploratory tests of combustion of other geometrically simple structures chosen to simulate other aspects of combustion of real propellants; (5) Systematic tests of a family of propellants to provide comparisons with results of tests on ordered structures; (6) development of a new analytical model for burning rate of propellants, based on the idea of determining the least-time-path for burning front to propagate through the microstructure from the burning surface to some relatively distant point in the propellant; (7) Development of a transient analysis of an axially symmetrical diffusion flame analogous to a burning oxidizer particle in a propellant matrix, and demonstration that the steady-state solution to this 'Burke-Schumann'-like problem is not dynamically stable (the complete analysis will be published separately); and (8) A restatement of the initial approach to the statistical model of propellant developed by Glick and Condon (presented to clarify the assumptions and method of the statistical approach). (Author).
LES of Sooting Flames ( Book )
2 editions published in 2006 in English and held by 1 library worldwide
Prediction of soot formation in turbulent flames is a major challenge due to the chemical complexity and the barely understood coupling between soot formation and the other flow transient processes. The current objective is to develop a unified, general methodology for large-eddy simulation (LES) of soot formation and transport in turbulent flames.
A New Approach to Validate Subgrid Models in Complex High Reynolds Number Flows ( Book )
2 editions published between 1994 and 1996 in English and held by 1 library worldwide
A dynamic sub grid model was developed by using a method that employed the scale similarity concept for validating the behavior of the subgrid models. Since the scale similarity approach can be used directly in the physical space, there was no need to employ spectral space information for implementing the subgrid model (although spectral space analysis was carried out to compare with past models). Thus, the new dynamic approach has potential for application to more complex flows. The key feature of the dynamic model is that it is a truly local model and does not require any type of averaging for a range of flow problems. The flow fields where no averaging was required are: (1) Taylor-Green flow, (2) decaying isotropic turbulence, (3) forced isotropic turbulence, (4) temporal mixing layers and, (5) free circular jet with axial entrainment.
Fractal Image Compression of Rayleigh, Raman, LIF and LDV Data in Turbulent Reacting Flows ( Book )
2 editions published between 1990 and 1991 in English and held by 1 library worldwide
Experiments and analysis were completed concerning a diagnostic program on a two dimensional subsonic wind tunnel with a backward facing step and combustion. Combustibles were introduced as a hydrogen-argon mixture from a porous floor behind the step. Completed were LDV and Raman spectroscopy for mean and rms velocity (two components) and temperature. Analysis used a two equation turbulence model which predicted the gross features of the flow but somewhat underpredicted reattachment length. Two dimensional and three dimensional fractal interpolation techniques were developed for reduction of noise to signal ratio in the complex turbulent flow. New methods of fractal analysis of time series were developed.
Combustion Instability in Solid Propellant Rockets ( Book )
2 editions published between 1987 and 1989 in English and held by 1 library worldwide
This project concerns assembly, synthesis and comprehensive presentation of information on combustion instability in solid rockets, in the form of a reference book. The format is chosen to make the book suitable for a wide audience of readers including propulsion program managers, motor designers, propellant chemists, test engineers, and combustion specialists. The diversity of audience is accommodated by opening with general introductory chapters for nonspecialist, with progression into more applied issues, such as experimental methods and remedial measures. All chapters open with Introductions that give a relatively non-technical statement of the problem and content, and end with a qualitative summary of what was done in the chapter. An extensive bibliography is included, and supplemented by a more complete, computer-based bibliography with search-retrieval capability.
Sublaminate Damage Mechanisms in Composite Structures ( Book )
2 editions published between 1986 and 1987 in English and held by 1 library worldwide
This interim report briefly summarizes the objectives, accomplishments and current direction of research on sublaminate damage mechanisms in composite structures. A Mode I suppression series of experiments and a companion analysis have been completed for graphite-epoxy double cracked-lap-shear specimens. The results show that a very small transverse normal force, 1-3% of the axial tensile force, is all that is needed to suppress Mode I action in interlaminar fracture. Complementary experiments on low cycle fatigue in tension and compression and on Mode I suppression in tension have been performed. The former confirm earlier static findings. The latter are also in agreement with static findings and illustrate the effectiveness of Mode I suppression technology. A practical working approach to analysis and design against delamination has been formulated. A simple fracture law is found to represent the existing data on four graphite-epoxy material systems and one glass-epoxy system created by a number of investigators on a variety of types of specimens. It has an intrinsic means of accounting for the observed high scatter of high Mode II (or Mode III), low Mode I delamination found in experiments. Keywords: Delamination, Interlaminar fracture, Damage in composites, Composite materials.
Two Approaches to the Three-Dimensional Jet-In-Cross Wind Problem: A Vortex Lattice Model and a Numerical Solution of the Navier-Stokes Equations ( Book )
2 editions published in 1971 in English and held by 1 library worldwide
A three-dimensional numerical solution of the time-dependent, incompressible Navier-Stokes equations based on an integro-differential formulation of these equations is developed. With this formulation it is possible to obtain the complete solution in the entire flow field while restricting the actual computational field to the region of significant vorticity magnitude of each time. This allows a considerable reduction in the computer storage required, since only the field points having significant vorticity at any time need be stored at that time, and calculations are actually performed only at those points at that time. The validity of the numerical solution is established by comparison of the results with the exact solution for the time-dependent, one-dimensional flow over a suddenly accelerated infinite flat plate moving parallel to itself at constant velocity, and by comparison of surface pressure and drag coefficients with experimental results, and with the results of other numerical solutions for the two-dimensional flow about a circular cylinder. The numerical solution is applied to the flow field of an infinite jet in a cross-flow and to the flow field of a jet issuing perpendicularly from an infinite plane wall into a cross-flow parallel to the wall. (Author).
Combustion of Ammonium Perchlorate-Polymer Sandwiches ( Book )
2 editions published between 1983 and 1984 in English and held by 1 library worldwide
A series of experimental studies of combustion of sandwiches is reported, and the results are used to develop a relatively detailed qualitative model for the combustion zone microstructure.
Studies in Low Speed Flight ( Book )
2 editions published in 1973 in English and held by 1 library worldwide
Research studies on problems in low speed flight conducted under the THEMIS program are summarized for the period from 1 October 1967 to 31 May 1973. Results of investigations on heavily loaded ducted fans, vortex-wake analysis of a single-bladed hovering rotor, rotor blade flutter analyses, jet-in-crosswind, wall jets, and instability in tensioned sheets with cutouts are described. Lists of publications which describe the research are given and the faculty and student participation in the program is summarized. (Author).
Behavior of Aluminum in Solid Propellant Combustion ( Book )
2 editions published between 1976 and 1977 in English and held by 1 library worldwide
The usefulness of powdered aluminum as a propellant ingredient is compromised by the details of its behavior in the combustion zone, its combustion in the motor volume, and by the nature of the product oxide droplets. This project was aimed at clarification of the mechanisms governing concentration, sintering and agglomeration of aluminum on the propellant burning surface, subsequent combustion of agglomerated aluminum, and resulting size distribution of the A1203 product droplets. The approach was to study the response of individual propellant ingredients, and combinations, to controlled heating in laboratory experiments such as hot stage microscope and hot plate apparatus.
Experiments and Analysis Related to External Burning for Propulsion ( Book )
2 editions published between 1976 and 1977 in English and held by 1 library worldwide
The results of first year's efforts on an experimental base flow program are reported. The design and checkout for a Mach 3.0 axisymmetric wind tunnel with a model base diameter of 2.25 inches is described, as well as the automated data acquisition system. Experiments are reported on detailed static pressures for the diffuser wall, model wall and base and near wake. Temperature measurements are presented to establish a near adiabatic wall condition. The relationship between the experimental program and propulsive external burning is discussed.