A color Schlieren system
Color schlieren photographic system for analysis of complex compressible fluid flows
FLUID MECHANICS↗
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Results for “complexity analysis”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Ultrasonics used to measure residual stress
Ultrasonic method is used to measure residual stress in metal structures. By using this method, various forms of wave propagation in metals are possible, and more thorough analysis of complex geometric structures may be had.
Source record↗
NASTRAN: Users' Experiences
The maintenance and development of NASTRAN has been centralized at the Langley Research Center in the NASTRAN Systems Management Office (NSMO ). Several important system improvements are in progress which will result in a significant reduction of average computer run time. The maintenance contractor, MacNeal-Schwendler, is also engaged in the addition of comprehensive substructuring capability. A dummy element capability which allows the test, evaluation, checkout, and temporary use of a new element in the NASTRAN environment is also underway and planned for inclusion in Level 15. Several new elements and a comprehensive heat transfer capability are in development under a contract with the Bell Aerospace Company. These enhancements are planned for inclusion in Level 16. In summary, NASTRAN has emerged as a powerful , generalized facility for the analysis of complex aerospace structures and is rapidly gaining acceptance from the community of aerospace and industrial users. NASA is, therefore, committed to manage and maintain the NASTRAN system as a valuable national resource.
Phillip R Wilcox↗
Space Shuttle: The Need for Substructuring
NASTRAN and substructuring techniques for structural analysis of complex space shuttle structures
H R Grooms↗
Numerical analysis of stagnation point flows with massive blowing
Numerical analysis of complex boundary layer at axisymmetric stagnation point with massive blowing
Libby, P. A.↗
Apparatus for statistical time-series analysis of electrical signals
An apparatus for performing statistical time-series analysis of complex electrical signal waveforms, permitting prompt and accurate determination of statistical characteristics of the signal is presented.
Stewart, C. H.↗
Reduction of truncation errors in modal analysis
A condensation method and computer program are described for large discrete parameter vibration analysis of complex structures that greatly reduces truncation errors and provides accurate definition of modes in a selected frequency range. A dynamic transformation is obtained from the partitioned equations of motion that relates modes not explicitly in the condensed solution to the retained modes at a selected system frequency. The generalized mass and stiffness matrices, obtained with existing modal synthesis methods, are reduced using this transformation and solved. Revised solutions are then obtained using new transformations at the calculated eigenvalues and are also used to assess the accuracy of the results. Computations are made tractable by simplified forms of the transformation that result with various modal synthesis methods. Three examples using the dynamic transformation in conjunction with a General Electric stiffness coupling method and the method of Craig and Bampton indicate large reductions in truncation errors and demonstrate the method for sequential groups of modes.
Kuhar, E. J.↗
A dynamic transformation method for modal synthesis.
This paper presents a condensation method for large discrete parameter vibration analysis of complex structures that greatly reduces truncation errors and provides accurate definition of modes in a selected frequency range. A dynamic transformation is obtained from the partitioned equations of motion that relates modes not explicity in the condensed solution to the retained modes at a selected system frequency. The generalized mass and stiffness matrices, obtained with existing modal synthesis methods, are reduced using this transformation and solved. Revised solutions are then obtained using new transformations at the calculated eigenvalues and are also used to assess the accuracy of the results. If all the modes of interest have not been obtained, the results are used to select a new set of retained coordinates and a new transformation frequency, and the procedure is repeated for another group of modes.
Kuhar, E. J.↗
NASTRAN data generation of helicopter fuselages using interactive graphics
The development and implementation of a preprocessor system for the finite element analysis of helicopter fuselages is described. The system utilizes interactive graphics for the generation, display, and editing of NASTRAN data for fuselage models. It is operated from an IBM 2250 cathode ray tube (CRT) console driven by an IBM 370/145 computer. Real time interaction plus automatic data generation reduces the nominal 6 to 10 week time for manual generation and checking of data to a few days. The interactive graphics system consists of a series of satellite programs operated from a central NASTRAN Systems Monitor. Fuselage structural models including the outer shell and internal structure may be rapidly generated. All numbering systems are automatically assigned. Hard copy plots of the model labeled with GRID or elements ID's are also available. General purpose programs for displaying and editing NASTRAN data are included in the system. Utilization of the NASTRAN interactive graphics system has made possible the multiple finite element analysis of complex helicopter fuselage structures within design schedules.
Sainsbury-Carter, J. B.↗
REDUCE 2: A computer program for the symbolic reduction of large block diagrams
REDUCE 2 is reported as a FORMAC program which symbolically calculates the transfer function(s) of any linear-block-diagram output variable to any or all input variables. The program requires as input a set of algebraic expressions representing the block diagram, the desired transfer function(s), and a string of variables indicating the desired order of reduction. The solution is presented in the compact form of a set of nested functions (super G's). The program can handle systems as large as 600 equations and is intended as a tool for the analysis of complex control and dynamic systems. A companion FORTRAN program, EVAL 2, which numerically evaluates the solution set to obtain amplitude ratio and phase angle as functions of frequency is also presented.
Lorenzo, C. F.↗
Inadvertent weather modification by Chicago-northern Indiana pollution sources observed by ERTS-1
Discussion of an apparent case of cloud modification by the effluents from numerous industrial sites in the Chicago-Gary complex. An analysis is made of a series of ERTS-1 images taken over Lake Michigan on Nov. 24, 1972, which apparently show modification of 1.5-km-wide cumulus cloud streets by the effluents of the industries at the southern end of the lake. A close inspection of these images reveals numerous interesting phenomena, the most important of which is the apparent alteration of the cumulus clouds along the axis of the major pollution plumes.
Lyons, W. A.↗
EMGAN: A computer program for time and frequency domain reduction of electromyographic data
An experiment in electromyography utilizing surface electrode techniques was developed for the Apollo-Soyuz test project. This report describes the computer program, EMGAN, which was written to provide first order data reduction for the experiment. EMG signals are produced by the membrane depolarization of muscle fibers during a muscle contraction. Surface electrodes detect a spatially summated signal from a large number of muscle fibers commonly called an interference pattern. An interference pattern is usually so complex that analysis through signal morphology is extremely difficult if not impossible. It has become common to process EMG interference patterns in the frequency domain. Muscle fatigue and certain myopathic conditions are recognized through changes in muscle frequency spectra.
Hursta, W. N.↗
Modeling of turbine blade tip contact
A mathematical model is developed to evaluate a number of physical effects in turbomachine blade tip contact on the basis of a broad brush approach to provide insights without undue complexity. The analysis is restricted to the case of a shoe encountering a moving blade row and pressing against it with a fixed time-average force. Relative displacement components in the contact region are identified and determined. Two key equations are derived, where it is shown that wear rate plays a strong role in determining the traversal speed of the contact patch. The formula for estimating the size of the contact patch shows that the higher the traversal speed is, the wider is the contact patch.
Burton, R. A.↗
Electron detachment from negative ions - The effects of isotopic substitution
Absolute total electron-detachment cross sections and relative elastic-scattering cross sections are presented for collisions of H(-) or D(-) with He, Ne, Ar, and N2 for collision energies ranging from about 2 eV up to 100 eV. Special emphasis has been given to the effect of isotopic substitution. It was found that, with the exception of the helium target, the results cannot be in accord with a model using a localized complex potential. On the other hand, the results for H(-) or D(-) with He are in excellent agreement with predictions based on previous (local complex potential) analysis of differential elastic-scattering measurements.
Champion, R. L.↗
Scramjet nozzle design and analysis as applied to a highly integrated hypersonic research airplane
Engine-nozzle airframe integration at hypersonic speeds was conducted by using a high-speed research aircraft concept as a focus. Recently developed techniques for analysis of scramjet-nozzle exhaust flows provide a realistic analysis of complex forces resulting from the engine-nozzle airframe coupling. By properly integrating the engine-nozzle propulsive system with the airframe, efficient, controlled and stable flight results over a wide speed range.
Small, W. J.↗
Storage and retrieval of mass spectral information
Computer handling of mass spectra serves two main purposes: the interpretation of the occasional, problematic mass spectrum, and the identification of the large number of spectra generated in the gas-chromatographic-mass spectrometric (GC-MS) analysis of complex natural and synthetic mixtures. Methods available fall into the three categories of library search, artificial intelligence, and learning machine. Optional procedures for coding, abbreviating and filtering a library of spectra minimize time and storage requirements. Newer techniques make increasing use of probability and information theory in accessing files of mass spectral information.
Hohn, M. E.↗
Lewis hybrid computing system, users manual
The Lewis Research Center's Hybrid Simulation Lab contains a collection of analog, digital, and hybrid (combined analog and digital) computing equipment suitable for the dynamic simulation and analysis of complex systems. This report is intended as a guide to users of these computing systems. The report describes the available equipment' and outlines procedures for its use. Particular is given to the operation of the PACER 100 digital processor. System software to accomplish the usual digital tasks such as compiling, editing, etc. and Lewis-developed special purpose software are described.
Bruton, W. M.↗
SAINT: A combined simulation language for modeling man-machine systems
SAINT (Systems Analysis of Integrated Networks of Tasks) is a network modeling and simulation technique for design and analysis of complex man machine systems. SAINT provides the conceptual framework for representing systems that consist of discrete task elements, continuous state variables, and interactions between them. It also provides a mechanism for combining human performance models and dynamic system behaviors in a single modeling structure. The SAINT technique is described and applications of the SAINT are discussed.
Seifert, D. J.↗