Validity of the electrostatic approximation
Existence criteria for normal modes in magnetized plasma related to electrostatic approximation
Montgomery, D.↗
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Results for “Normal modes”
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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The theory of incomplete models of dynamic structures
Limited frequency range analytical model for predicting mass and stiffness changes effect on natural frequencies and normal modes
Berman, A.↗
Interactions of waves and particles in an inhomogeneous one-dimensional plasma
Inhomogeneous one dimensional plasma in electrostatic normal modes, considering interactions of waves and particles
Kaufman, A. N.↗
Unified hatch system
Special hatch sealing mechanism design increases safety, reliability, and convenience. Adaptations are possible for oceanographic and high-speed aircraft design, or for any system where quick-opening pressure hatch is required. In normal mode, hatching mechanism is manually operated from either side.
Hart, R. J.↗
Study of vibrational excitation mechanisms of CO2 at high temperatures
Calculating vibrational excitation of CO2 for anharmonic coupling and normal mode at high temperature
Rehm, R. G.↗
Interpretation of dispersion relations for bounded systems
Constructing normal modes for bounded systems from infinite dispersion relation roots for interpretation of plasma wave and instability studies on finite cylinders
Rognlien, T. D.↗
Kelvin instability in a composite hydromagnetic system
Two component hydromagnetic system Kelvin instability due to tangential velocities discontinuity, using normal mode analysis
Talwar, S. P.↗
The response of a simply supported plate to 'N' waves at oblique incidence
Simply supported normal mode plate time response to traveling wave at oblique incidence, using numerical analysis
Craggs, A.↗
Free vibrations of a linear structure with arbitrary support conditions
Free vibrations of linear structure with arbitrary support by Rayleigh-Ritz method using unconstrained normal modes
Dowell, E. H.↗
Response of a panel structure to reverberant acoustic excitation
Investigation was made of methods for predicting response of panel structures to acoustic excitation. Computer program was generated to calculate response of panel to reverberant acoustic field, using normal mode approach developed for low frequency response. Program can be modified to handle other types of acoustic fields by changing spatial correlation calculation.
Cadin, D., Jr.↗
Response of aerospace structures to reentry aerodynamic excitation
A bibliography on aerodynamic excitation and associated structural response is presented. Very little applicable data under actual reentry conditions was found, but many wind tunnel tests and some in-flight data were. Aerodynamic excitation and proposed space shuttle configurations and reentry trajectories were studied. Attached turbulent boundary layer, separated turbulent boundary layer, and base pressure fluctuations are the region of aerodynamic excitation most applicable to exterior panels of space shuttle-type vehicles; prediction techniques are presented for these environments. Methods for predicting the response of panel structures to acoustic excitation were investigated. A normal mode approach was developed for the low frequency response and a statistical energy approach was utilized for the high frequency response. A finite element model was made of a thermal protective system test panel. Computer programs were used to determine the natural frequencies and mode shapes of the panel and to calculate the response of the panel to a reverberant acoustic field. Power spectral densities of response displacement and acceleration are presented.
Carlin, D., Jr.↗
Quiet-time observation of a coherent compressional Pc-4 micropulsation at synchronous altitude
During a magnetically quiet interval the magnetic-field intensity and energetic electron fluxes at ATS 1 exhibited coherent modulations having a frequency of 33.8 cph and a duration of approximately 40 oscillations. The electron fluxes and the magnetic field oscillated in phase. The field perturbation reached 8 jamma (peak to peak) in the direction of the unperturbed geomagnetic field. The transverse component of the field perturbation was practically zero. The characteristics of the observed oscillations appear compatible with those of a compressional excitation of the outer magnetosphere. The substantially radial normal mode is perhaps driven by a bounce-resonant interaction with the 15-keV protons that populate the quiet-day ring current.
Paulikas, G. A.↗
Blade frequency program for nonuniform helicopter rotors, with automated frequency search
A computer program for determining the natural frequencies and normal modes of a lumped parameter model of a rotating, twisted beam, with nonuniform mass and elastic properties was developed. The program is used to solve the conditions existing in a helicopter rotor where the outboard end of the rotor has zero forces and moments. Three frequency search methods have been implemented. Including an automatic search technique, which allows the program to find up to the fifteen lowest natural frequencies without the necessity for input estimates of these frequencies.
Sadler, S. G.↗
Pressure-fluctuation inputs and response of panels underlying attached and separated supersonic turbulent boundary layers
Results are presented for an investigation of surface pressure fluctuations and response of panels underlying attached and separated turbulent boundary layers and shock waves. Tests conducted at transonic and supersonic Mach numbers to 3.6 to study the pressure fields. Assorted fixed edge flat panels were tested at Mach numbers from 1.6 to 3.6 in attached and completely separated flow fields, and also in mixed flow with a step-induced shock wave oscillating on the panels. The surface pressure fluctuations are described in terms of broadband rms, spectral density, and spatial correlation information. The effectiveness of parameters for scaling the pressure fluctuations is also illustrated. Measurements of the amplitude and strain response of the panels are compared with response computations by the normal mode method of analysis.
Coe, C. F.↗
Experiences in interfacing NASTRAN with another finite element program
The coupling of NASTRAN to another finite element program developed for the static analysis of automotive structures is discussed. The two programs were coupled together to use the substructuring capability of the in-house program and the normal mode analysis capability of NASTRAN. Modifications were made to the NASTRAN program in order to make the coupling feasible.
Schwerzler, D. D.↗
Applications of NASTRAN to nuclear problems
The extent to which suitable solutions may be obtained for one physics problem and two engineering type problems is traced. NASTRAN appears to be a practical tool to solve one-group steady-state neutron diffusion equations. Transient diffusion analysis may be performed after new levels that allow time-dependent temperature calculations are developed. NASTRAN piecewise linear anlaysis may be applied to solve those plasticity problems for which a smooth stress-strain curve can be used to describe the nonlinear material behavior. The accuracy decreases when sharp transitions in the stress-strain relations are involved. Improved NASTRAN usefulness will be obtained when nonlinear material capabilities are extended to axisymmetric elements and to include provisions for time-dependent material properties and creep analysis. Rigid formats 3 and 5 proved to be very convenient for the buckling and normal-mode analysis of a nuclear fuel element.
Spreeuw, E.↗
Convective envelopes and radial pulsation of massive red supergiants.
A grid of convective envelope models covering a wide range of astrophysical parameters has been constructed for M-type supergiants with the help of theoretical evolutionary tracks, mixing-length theory, and the inclusion of hydrogen and helium ionization zones. Linear adiabatic pulsation theory has been used to obtain the first four normal modes of radial pulsation for all the models. All the convective envelopes are found to be dynamically stable. The theoretical pulsation calculations confirm that the primary observed period in variable M-type supergiants is probably due to the fundamental mode of radial pulsation.
Stothers, R.↗
General theory of spherically symmetric boundary-value problems of the linear transport theory.
A general theory of spherically symmetric boundary-value problems of the one-speed neutron transport theory is presented. The formulation is also applicable to the 'gray' problems of radiative transfer. The Green's function for the purely absorbing medium is utilized in obtaining the normal mode expansion of the angular densities for both interior and exterior problems. As the integral equations for unknown coefficients are regular, a general class of reduction operators is introduced to reduce such regular integral equations to singular ones with a Cauchy-type kernel. Such operators then permit one to solve the singular integral equations by the standard techniques due to Muskhelishvili. We discuss several spherically symmetric problems. However, the treatment is kept sufficiently general to deal with problems lacking azimuthal symmetry. In particular the procedure seems to work for regions whose boundary coincides with one of the coordinate surfaces for which the Helmholtz equation is separable.
Kanal, M.↗