SEARCH · Engineering Papers
Results for “Wave”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Particle-in-cell Monte Carlo-collision modeling of non-ideal effects in wave-heated dense microplasmas
A computational model for non-ideal plasma effects during the time evolution of a second-stage laser-heated discharge at high pressures is presented. The model extends a classical one-dimensional particle-in-cell Monte Carlo-collision (PIC-MCC) approach coupled with Maxwell's equations for the laser-heating process of a xenon plasma at 300 K temperature and 10–100 bar pressure. Plasma non-ideality resulting from Coulomb coupling at high plasma densities is manifested as a depression in the effective ionization potential of atoms and enhanced collision cross sections. These non-ideal effects are represented using the Ecker–Kröll model in the context of the PIC-MCC approach. We find that full ionization of the plasma is obtained on the picosecond timescale, starting from the skin layer and quickly expanding throughout the domain through an anomalous extension of the skin depth. More critically, we show that the inclusion of the non-ideal plasma effects results in more rapid ionization compared to an ideal plasma, especially at higher pressures. The ionization delay reduction is of the order of a fraction of a picosecond, corresponding to a 16% decrease at 100 bar. As the amplitude of the wave field is lowered, the ionization rate is lowered, making the plasma non-ideality effects more prominent.
Post-compression of multiterawatt long-wave infrared pulses
Explore the source record for details and available documents.
A study of longitudinal oscillations of propellant tanks and wave propagations in feed lines. Part 1 - Propagating pressure waves in a fluid-filled cylindrical shell
Theory and equations for propagating pressure waves in liquid filled cylindrical shells
Electromagnetic wave propagation in a dielectric medium space-time modulated by a nonlinear pump wave.
Dispersion relation involving space-time harmonics obtained for electromagnetic wave propagation in dielectric medium
Plasma wave measurements for the Mariner to Venus and Mercury Final report of the Plasma Wave Instrument Science Advisory Team for the 1973 Mercury/Venus mission design
Very low frequency electric and magnetic wave measurements for Mariner Venus Mercury 1973 mission
Flow perturbations generated by a shock wave interacting with an entropy wave
Numerical results for perturbed downstream flow field resulting from entropy wave interaction with normal shock and oblique shock generated by wedge flow
Elastic waves guided by a fluid layer - A new type of ultrasonic wave propagation
Ultrasonic wave propagation guided by fluid layer between two elastic solids, plotting normalized velocities and layer thicknesses
Wave coupling across a shock wave in a viscous plasma
Electron-acoustic, ion-acoustic and electromagnetic plane waves coupling at shock front in two fluid ionized viscous plasma
Changes in heat transfer from turbulent boundary layers interacting with shock waves and expansion waves
Heat transfer from turbulent boundary layer interacting with shock and expansion waves in supersonic flow
Ogo 5 observations of upstream waves in the interplanetary medium - Discrete wave packets
Upstream discrete wave packets propagation interplanetary medium from Ogo 5 observation
On the motion and radiation of charged particles in strong electromagnetic waves. I - Motion in plane and spherical waves
Charge particle motion and radiation in strong plane and spherical electromagnetic waves with nonthermal astrophysical applications
Low-frequency waves and instabilities on the positive column in a magnetic field. V - Axisymmetric ionization waves
Homogeneous positive plasma column perturbation analysis in axial magnetic field, deriving model for ionization waves dispersion characteristics
Wave-front singularities for two-dimensional anisotropic elastic waves.
Wavefront singularities for the displacement functions, associated with the radiation of linear elastic waves from a point source embedded in a finitely strained two-dimensional elastic solid, are examined in detail. It is found that generally the singularities are of order d to the -1/2 power, where d measures distance away from the front. However, in certain exceptional cases singularities of order d to the -n power, where n = 1/4, 2/3, 3/4, may be encountered.
A wave-envelope technique for wave propagation in non-uniform ducts
The method of variation of parameters is used to analyze wave propagation in variable area, plane ducts with no mean flow. The method has an explicit representation of the fast axial variation of the acoustic modes, and numerical integration is required only for the slower axial variations of the mode amplitudes and phases. Results are presented which demonstrate the numerical advantages of the method. Comparison of the results with those of a small perturbation theory are given. The relationship between this method and the method of weighted residuals is discussed.
Analysis of upper mantle structure using wave field continuation of P waves
Wave field continuation theory, which allows transformation of the seismic record section data directly into velocity-depth space, is tested for upper mantle analysis using a large array-recorded data set obtained at the 200-station Caltech-USGS Southern California Seismic Network that is representative of the structure beneath the gulf of California. The method's resolution capability is illustrated by the comparison of the slant stacks and downward continuation of both synthetic and data record sections. It is stressed that when high-quality, densely sampled digital data are available, the technique is easy to implement, provides an inversion which contains all the data in the global format, and produces an objective estimate of depth resolution as a function of ray parameter.
ELF wave production by an electron beam emitting rocket system and its suppression on auroral field lines - Evidence for Alfven and drift waves
Orthogonal probes on a free-flying plasma diagnostics payload are used to study ELF electric disturbances in the auroral ionosphere that are due to the injection of powerful electron beams. Frequency spectrograms are presented for various pitch angles, pulsing characteristics, and other properties of the injected beams; the large scale DC ionospheric convection electric field is measured, together with auroral particle precipitation, visual auroral forms, and ionospheric parameters. In view of the experimental results obtained, it is postulated that the observed ELF waves are in the Alfven and drift modes, and are generated by the positive vehicle potential during beam injection.
Scattering of acoustic waves into Tollmien-Schlichting waves by small streamwise variations in surface geometry
By using the triple-deck scaling of Stewartson (1969) and Messiter (1970) it is shown that small but relatively sudden surface geometry variations that produce only very weak static pressure variations can nevertheless produce strong, i.e. O(1), coupling between an externally imposed acoustic disturbance and a spatially growing Tollmien-Schlichting wave. The analysis provides a qualitative explanation of the Leehey and Shapiro (1979) boundary-layer receptivity measurements and is in good quantitative agreement with the Aizin and Poliakov (1979) experiment. It may also explain why small 'trip wires' can promote early transition.