Three-wave interaction in a beam-plasma system
Coupling coefficient derived for three-wave interaction in beam plasma system
Hopman, H. J.↗
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Results for “Derivative couplings”
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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RCS jet-flow field interaction effects on the aerodynamics of the space shuttle orbiter
A study was conducted to determine the external effects caused by operation of the reaction control system during entry of the space shuttle orbiter. The effects of jet plume-external flow interactions were emphasized. Force data were obtained for the basic airframe characteristics plus induced effects when the reaction control system is operating. Resulting control amplification and/or coupling were derived and their effects on the aerodynamic stability and control of the orbiter and the reaction control system thrust were determined.
Rausch, J. R.↗
Partition function corrections
The vibration-rotation interaction coupling in diatomic molecules is analyzed and first-order expressions for the energy levels are deduced. Corrections to the partition function to account for this coupling are derived. The effects of long-range intermolecular forces due to induced dipole-induced dipole interactions, dipole-induced dipole interactions, charge-dipole interactions, and charge-charge interactions are considered. London's quantized oscillator model of the induced dipole-induced dipole interaction is developed. The partition function including effects of such dispersion forces is derived and is shown to lead to the virial equation of state. For a model combining the hard sphere and long-range attractive type potentials, this is found to lead to the van der Waals equation of state. The equation of state near the critical point is presented in reduced form (thermodynamic variables expressed in units of critical point values). Finally, approximate corrections to the electronic partition functions are derived to account for perturbations of excited electronic states induced by neighboring neutral particles, heavy ions, and fast electron collisions.
Source record↗
The coupled states approximation for scattering of two diatoms
The paper presents a detailed development of the coupled-states approximation for the general case of two colliding diatomic molecules. The high-energy limit of the exact Lippman-Schwinger equation is applied, and the analysis follows the Shimoni and Kouri (1977) treatment of atom-diatom collisions where the coupled rotor angular momentum and projection replace the single diatom angular momentum and projection. Parallels to the expression for the differential scattering amplitude, the opacity function, and the nondiagonality of the T matrix are reported. Symmetrized expressions and symmetrized coupled equations are derived. The present correctly labeled coupled-states theory is tested by comparing its calculated results with other computed results for three cases: H2-H2 collisions, ortho-para H2-H2 scattering, and H2-HCl.
Heil, T. G.↗
Phytanyl-glycerol ethers and squalenes in the archaebacterium Methanobacterium thermoautotrophicum
Gas chromatographic and mass- and infrared-spectrometric techniques are used to assay the lipids of a thermophilic chemolithotroph, Methanobacterium thermoautotrophicum. Of the chloroform-soluble lipids, 79% are polar and 21% non-polar. Attention is given to the detection of squalene and hydrosqualene derivatives, which, coupled with 16S r-RNA sequence homologies, indicate that the extreme halophiles and the methanogens share a common ancestor.
Tornabene, T. G.↗
Two-photon excitation cross-section in light and intermediate atoms
The method of explicit summation over the intermediate states is used along with LS coupling to derive an expression for two-photon absorption cross section in light and intermediate atoms in terms of integrals over radial wave functions. Two selection rules, one exact and one approximate, are also derived. In evaluating the radial integrals, for low-lying levels, the Hartree-Fock wave functions, and for high-lying levels, hydrogenic wave functions obtained by the quantum defect method are used. A relationship between the cross section and the oscillator strengths is derived. Cross sections due to selected transitions in nitrogen, oxygen, and chlorine are given. The expression for the cross section is useful in calculating the two-photon absorption in light and intermediate atoms.
Omidvar, K.↗
Development of a rotorcraft. Propulsion dynamics interface analysis, volume 2
A study was conducted to establish a coupled rotor/propulsion analysis that would be applicable to a wide range of rotorcraft systems. The effort included the following tasks: (1) development of a model structure suitable for simulating a wide range of rotorcraft configurations; (2) defined a methodology for parameterizing the model structure to represent a particular rotorcraft; (3) constructing a nonlinear coupled rotor/propulsion model as a test case to use in analyzing coupled system dynamics; and (4) an attempt to develop a mostly linear coupled model derived from the complete nonlinear simulations. Documentation of the computer models developed is presented.
Hull, R.↗
Closed-form solutions for a class of optimal quadratic regulator problems with terminal constraints
Closed-form solutions are derived for coupled Riccati-like matrix differential equations describing the solution of a class of optimal finite time quadratic regulator problems with terminal constraints. Analytical solutions are obtained for the feedback gains and the closed-loop response trajectory. A computational procedure is presented which introduces new variables for efficient computation of the terminal control law. Two examples are given to illustrate the validity and usefulness of the theory.
Juang, J.-N.↗
Calculations of separation bubbles using boundary-layer-type equations. I. II
Two-dimensional models of separated flows are presented with stream-function boundary equations. A patching procedure is employed to solve for unknowns in viscous-inviscid interactions simultaneously in order to derive strong coupling. The technique features simplified Navier-Stokes equations and is useful for flows around flat plates and more complex geometries such as airfoils and cascades. Sample calculations are provided for separated flows in diffusers and in the neighborhood of trailing edges. Massive bubbles and unclosed bubbles are noted to present difficulties for the models.
Halim, A.↗
On the nonlinear interaction of Gortler vortices and Tollmien-Schlichting waves in curved channel flows at finite Reynolds numbers
The flow in a two-dimensional curved channel driven by an azimuthal pressure gradient can become linearly unstable due to axisymmetric perturbations and/or nonaxisymmetric perturbations depending on the curvature of the channel and the Reynolds number. For a particular small value of curvature, the critical neighborhood of this curvature value and critical Reynolds number, nonlinear interactions occur between these perturbations. The Stuart-Watson approach is used to derive two coupled Landau equations for the amplitudes of these perturbations. The stability of the various possible states of these perturbations is shown through bifurcation diagrams. Emphasis is given to those cases which have relevance to external flows.
Daudpota, Q. Isa↗
Interaction of Gortler vortices and Tollmien-Schlichting waves in curved channel flow
The flow in a two-dimensional curved channel driven by an azimuthal pressure gradient can become linearly unstable due to axisymmetric perturbations and/or nonaxisymmetric perturbations depending on the curvature of the channel and the Reynolds number. For a particular small value of curvature, the critical Reynolds number for both these perturbations becomes identical. In the neighborhood of this curvature value and critical Reynolds number, nonlinear interactions occur between these perturbations. The Stuart-Watson approach is used to derive two coupled Landau equations for the amplitudes of these perturbations. The stability of the various possible states of these perturbations is shown through bifurcation diagrams. Emphasis is given to those cases which have relevance to external flows.
Daudpota, Q. Isa↗
On the nonlinear interaction of Goertler vortices and Tollmien-Schlichting waves in curved channel flows at finite Reynolds numbers
The flow in a two-dimensional curved channel driven by an azimuthal pressure gradient can become linearly unstable due to axisymmetric perturbations and/or nonaxisymmetric perturbations depending on the curvature of the channel and the Reynolds number. For a particular small value of curvature, the critical neighborhood of this curvature value and critical Reynolds number, nonlinear interactions occur between these perturbations. The Stuart-Watson approach is used to derive two coupled Landau equations for the amplitudes of these perturbations. The stability of the various possible states of these perturbations is shown through bifurcation diagrams. Emphasis is given to those cases which have relevance to external flows.
Daudpota, Q. Isa↗
Compliant Joints For Robots
Compliant joints devised to accommodate misalignments of tools and/or workpieces with respect to robotic manipulators. Has characteristics and appearance of both universal-joint and cable-spring-type flexible shaft coupling. Compliance derived from elastic properties of short pieces of cable. Compliance of joint determined by lengths, distances between, relative orientations, thickness of strands, number of strands, material, amount of pretwist, and number of short pieces of cable. Worm-drive mechanism used to adjust lengths to vary compliance as needed during operation.
Kerley, James J., Jr.↗
Development of a new model for vibration-dissociation coupling in nitrogen
A new model for vibration-dissociation coupling is derived using knowledge obtained from a simulation of the vibrational relaxation of heated nitrogen by collisional processes. This bilevel model is based on the assumption that nitrogen can be represented by two molecular species. The vibrational energy relaxation is represented by a modified form of the Landau-Teller equation. The effects of the bilevel model on a typical hypervelocity flowfield computation are examined and compared to the Park TTv model. Specifically, it is found that the bilevel model exhibits a decreased dissociation rate. This is believed to be due to the inhibition of dissociation by nonequilibrium vibrational relaxation.
Landrum, D. B.↗
Calculations of surface radiation in arid regions - A case study
The surface and satellite data measured during the preliminary field experiment for the Land-Atmosphere Interactions Experiment conducted at the Heihe River basin in western China are used to investigate the difficulties encountered in the derivation of the surface radiation budget in arid regions. The surface radiation is derived by coupling theoretical radiative transfer calculations with satellite cloud retrievals. For cloud-free cases, the modeled downward solar fluxes are systematically larger than the measured fluxes. It is found that the error can be reduced and that good agreement between the computed and measured surface solar fluxes can be obtained by using an aerosol single-scattering albedo of 0.5 and an optical thickness of about 0.2 in the afternoon hours. For all the cases studied when both surface and satellite data are available, the mean errors are 4.3 and -4.7 W/sq m for the net downward surface solar flux and the downward surface IR flux, respectively. The rms errors are 17.4 and 22.1 W/sq m for the respective surface fluxes. The importance of aerosols in surface radiation calculations is underscored.
Chou, Ming-Dah↗
Coupled 2-dimensional cascade theory for noise an d unsteady aerodynamics of blade row interaction in turbofans. Volume 2: Documentation for computer code CUP2D
A two dimensional linear aeroacoustic theory for rotor/stator interaction with unsteady coupling was derived and explored in Volume 1 of this report. Computer program CUP2D has been written in FORTRAN embodying the theoretical equations. This volume (Volume 2) describes the structure of the code, installation and running, preparation of the input file, and interpretation of the output. A sample case is provided with printouts of the input and output. The source code is included with comments linking it closely to the theoretical equations in Volume 1.
Hanson, Donald B.↗
Deuterium hyperfine structure in interstellar C3HD
The deuterium nuclear quadrupole hyperfine structure of the transition 1(10)-1(01) of the ring molecule cyclopropenylidene-d1 (C3HD) has been observed in emission from interstellar molecular clouds. The narrowest linewidths (approximately 7 kHz) so far observed are in the cloud L1498. The derived D coupling constants Xzz = 186.9(1.4) kHz, eta=0.063(18) agree well with correlations based on other molecules.
NASA Program Exobiology↗
Nonlinear interaction of plasma waves in a cold magnetized plasma.
Coupling equations are derived for the general case of nonlinear coupling of any wave modes in a cold magnetized plasma with particle drift motions. Specifically, the transformation of electrostatic waves is studied in connection with solar type-III radiation. A relevant numerical analysis is also presented.
Chin, Y.-C.↗