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NASA NTRS1982

The Burst and Transient Source Experiment for the Gamma-Ray Observatory

The Burst and Transient Source Experiment (BATSE) is a highly sensitive, all-sky monitor for the Gamma-Ray Observatory (GRO). The eight scintillation detector modules of BATSE are positioned around the GRO spacecraft to provide a uniform view of the entire sky above the horizon. Each module is 20 in. in diameter, 0.5 in. thick and operates in the energy range from 40 to 600 keV. Rough burst locations can be derived from the relative counting rates of the detectors; longer-lived (greater than 100 min) transient sources can be detected and located by earth occultations. The data system contains mass memory to allow storage of large amounts of burst data in short time intervals. Data are sorted onboard in various ways into programmable energy, time and detector domains. Details of the design and capabilities of the BATSE are presented.

Fishman, G. J.↗

NASA NTRS1983

Transient difference solutions of the inhomogeneous wave equation - Simulation of the Green's function

A time-dependent finite difference formulation to the inhomogeneous wave equation is derived for plane wave propagation with harmonic noise sources. The difference equation and boundary conditions are developed along with the techniques to simulate the Dirac delta function associated with a concentrated noise source. Example calculations are presented for the Green's function and distributed noise sources. For the example considered, the desired Fourier transformed acoustic pressures are determined from the transient pressures by use of a ramping function and an integration technique, both of which eliminates the nonharmonic pressure associated with the initial transient.

Baumeister, K. J.↗

NASA NTRS1982

A basic code for the prediction of transient three-dimensional turbulent flowfields

A primitive pressure-velocity finite difference code has been developed to predict transient three-dimensional turbulent flow. The code is a simplified yet effective prediction procedure for use by persons with little experience in computational fluid dynamics, and into which user-oriented complexities can easily be added. The method is based on the transient two-dimensional Los Alamos SOLA prediction technique for laminar flows. Turbulence is simulated by means of a two-equation turbulence model; species diffusion and buoyancy are also included. Two applications of the code are presented to local destratification near the release structure of a reservoir and to the deflection of a jet entering normally into a uniform cross-flow. Predicted results exhibit good agreement with experimental data, showing that a useful characterization of fully three-dimensional flows is now available.

Busnaina, A. A.↗

NASA NTRS1983

Irregular X-ray variability in the transient X-ray burst source MXB 1659-29

Irregular variability in the X-ray emission from MXB 1659-29 was observed with SAS 3 during the 1978 transient outburst of the source. No stable period can yet be derived from the low-intensity states, although there is evidence for a quasi-periodicity of either 1.2 or 1.4 hours. The low-intensity states observed in MXB 1659-29 during the transient outburst vary both in width and duration, similar to those in MXB 1916-05. The SAS 3 data are consistent with either the intermittent obscuration of the X-ray emitter by relatively cold gas or with scattering of the X-rays by hotter material.

Cominsky, L.↗

NASA NTRS1984

Preflight transient dynamic analyses of B-52 aircraft carrying Space Shuttle solid rocket booster drop-test vehicle

This paper concerns the transient dynamic analysis of the B-52 aircraft carrying the Space Shuttle solid rocket booster drop test vehicle (SRB/DTV). The NASA structural analysis (NASTRAN) finite element computer program was used in the analysis. The B-52 operating conditions considered for analysis were (1) landing and (2) braking on aborted takeoff runs. The transient loads for the B-52 pylon front and rear hooks were calculated. The results can be used to establish the safe maneuver envelopes for the B-52 carrying the SRB/DTV in landings and brakings.

Ko, W. L.↗

NASA NTRS1983

Transient thermal stresses in a reinforced hollow disk or cylinder containing a radial crack

The transient thermal stress problem in a hollow cylinder or a disk containing a radial crack is considered. It is assumed that the cylinder is reinforced on its inner boundary by a membrane which has thermoelastic constants different than those of the base material. The transient temperature, thermal stresses and the crack tip stress intensity factors are calculated in a cylinder which is subjected to a sudden change of temperature on the inside surface. The results are obtained for various dimensionless parameters and material constants. The special cases of the crack terminating at the cylinder-membrane interface and of the broken membrane are separately considered and some examples are given.

Tang, R.↗

NASA NTRS1984

Power spectral signatures of interplanetary corotating and transient flows

Studies of the time behavior of the galactic cosmic ray intensity have concluded that long term decreases in the intensity are generally associated with systems of interplanetary flows that contain flare generated shock waves, magnetic clouds and other transient phenomena. The magnetic field power spectral signatures of such flow systems are compared to power spectra obtained during times when the solar wind is dominated by stable corotating streams that do not usually produce long-lived reduction in the cosmic ray intensity. The spectral signatures of these two types of regimes (transient and corotating) are distinct. However, the distinguishing features are not the same throughout the heliosphere. In data collected beyond 1 AU the primary differences are in the power spectra of the magnitude of the magnetic field rather than in the power in the field components. Consequently, decreases in cosmic ray intensity are very likely due to magnetic mirror forces and gradient drifts rather than to small angle scattering due to cyclotron wave-particle interactions.

Goldstein, M. L.↗

NASA NTRS1984

On the role of the transient eddies in maintaining the seasonal mean circulation

The role of transient eddies in maintaining the observed local seasonal mean atmospheric circulation was investigated by examining the time-averaged momentum balances and omega equation, using seasonal statistics calculated from daily operational analyses by the European Centre for Medium Range Weather Forecasts. While both the Northern and Southern Hemispheres and several seasons were studied, emphasis was placed upon the Northern Hemisphere during December 1981-February 1982. The results showed that transient eddies played a secondary role in the seasonal mean zonal momentum budget and in the forcing of seasonal mean vertical and a geostrophic motion.

White, G. H.↗

NASA NTRS1984

Transient EHL Effects in Starved Ball Bearings

The independent variables used in most calculations for EHL film thickness in ball bearings involve lubricant properties, contact elasticity, load, and bearing kinematics. The calculations are for steady state, and they give a time-constant film thickness. Experiments have shown four distinct processes in starved ball bearings which are explainable assuming a time-varying film thickness. This contribution describes these four processes as well as another transient EHL effect which does not involve the thickness of the film. A simple model, based on experimental considerations, allows direct calculation of several of the thickness transients.

E Kingsbury↗

NASA NTRS1983

Modeling of transient two-component flow using a four-point implicit method

The four-point, centered implicit scheme that is extensively used in open channel flow simulation is shown to be applicable to rapid and slow pressure transient problems in conduits with nearly single phase and two-phase flows. It is only necessary to choose the proper weighting factor value, theta, of the Courant number. For rapid pressure transients such as waterhammer, the implicit method can yield reasonable results with limited numerical dispersion and attenuation if theta is only slightly greater than the critical value of 0.5. For slower pressure gradients in single and two-phase flows, reasonable numerical solutions may be achieved for Courant number values as high as 20.

Wiggert, D. C.↗

NASA NTRS1983

Transient decay times and mean values of unsteady oscillations in transonic flow

Kerlick and Nixon (1981) point out that if the time-marching solution is stopped before the transient is complete and the steady state is reached, then the incorrect conclusion may be reached that a change in the mean lift has occurred in response to the oscillating motion of the airfoil when in fact no such change has occurred. For a narrow Mach number range, however, the time for the transient to decay and for a steady state to be reached is extraordinarily long. What is more, for a very narrow range of Mach numbers, a nonzero mean value of lift can occur for an airfoil of symmetrical profile oscillations about a zero angle of attack. The reason why this nonzero average lift occurs only over a narrow range of Mach numbers has so far not been obtained.

Dowell, E. H.↗

NASA NTRS1983

Pre-flight transient dynamic analysis of B-52 carrying Space Shuttle solid rocket booster drop-test vehicle

This paper concerns the transient dynamic analysis of the B-52 aircraft carrying the Space Shuttle solid-rocket booster drop-test vehicle (SRB/DTV). The NASA structural analysis (NASTRAN) finite-element computer program was used in the analysis. The B-52 operating conditions considered for analysis were (1) landing and (2) braking on aborted takeoff runs. The transient loads for the B-52 pylon front and rear hooks were calculated. The results can be used to establish the safe maneuver envelopes for the B-52 carrying the SRB/DTV in landings and brakings.

Ko, W. L.↗

NASA NTRS1983

An eigenvalue method for solving transient heat conduction problems

The eigenvalue method, which has been used by researchers in structure mechanics, is applied to problems in heat conduction. Its formulation is decribed in terms of an examination of transient heat conduction in a square slab. Taking advantage of the availability of the exact solution, we compare the accuracy and other numerical properties of the eigenvalue method with those of existing numerical schemes. The comparsion shows that, overall, the eigenvalue method appears to be fairly attractive. Furthermore, only a few dominant eigenvalues and their corresponding eigenvectors need to be computed and retained to yield reasonably high accuracy. Greater savings are attained in the computation time for a transient problem with long time duration and a large computational domain.

Shih, T. M.↗

NASA NTRS1984

Transient behavior of flare-associated solar wind. II - Gas dynamics in a nonradial open field region

Transient behavior of flare-associated solar wind in the nonradial open field region is numerically investigated, taking into account the thermal and dynamical coupling between the chromosphere and the corona. A realistic steady solar wind is constructed which passes through the inner X-type critical point in the rapidly diverging region. The wind speed shows a local maximum at the middle, O-type, critical point. The wind's density and pressure distributions decrease abruptly in the rapidly diverging region of the flow tube. The transient behavior of the wind following flare energy deposition includes ascending and descending conduction fronts. Thermal instability occurs in the lower corona, and ascending material flows out through the throat after the flare energy input ceases. A local density distribution peak is generated at the shock front due to the pressure deficit just behind the shock front.

Nagai, F.↗

NASA NTRS1984

Power spectral signatures of interplanetary corotating and transient flows

Goldstein, M. L.↗

NASA NTRS1984

Type II bursts, shock waves, and coronal transients - The event of 1980 June 29, 0233 UT

The metric Type-II solar burst event of June 29, 1980, is characterized on the basis of spatially resolved radioheliograph observations obtained at Culgoora, Australia, and visible-light observations obtained with the coronograph/polarimeter of the SMM satellite. The data are presented in images, diagrams, and graphs and discussed in detail. The Type-II emission is found to arise in the dense moving material behind the transient loops, which have sky-plane width 0.5 solar radius and line-of-sight depth 0.1-0.4 solar radius. A faint arc observed moving ahead of the transient loops at about 900 km/sec and not associated with the Type-II burst is attributed to a shock front, and the compression ratio and Alfven Mach number of the enhanced-density region are estimated as n2/n1 = 1.3-3 and M(A) = 1.2-3. The ambient material at 3 solar radii is determined to have Alfven speed 250-625 km/sec and magnetic-field strength 50-120 mG. The total mass of the event is calculated as 700 Tg; the total magnetic energy of the loops is (1.5-15) x 10 to the 29th ergs.

Gary, D. E.↗

NASA NTRS1983

Mixed time integration schemes for transient conduction forced-convection analysis

A partition procedure for forced-convection conduction transient problems is presented. Mixed time partitions are defined wherein coupled conduction force-matrix equations are discretized using an implicit integration method, followed by derivation of a mixed time integration technique. Explicit-implicit and explicit-explicit partitions are performed for a stability analysis for transient conditions, e.g., those found in an actively air-cooled engine and airframe structure.

Liu, W. K.↗

NASA NTRS1984

A full-implicit-continuous-Eulerian (FICE) scheme for multidimensional transient magnetohydrodynamic (MHD) flows

A full implicit continuous Eulerian (FICE) scheme is developed for solving multidimensional transient MHD flow problems. The physical system under consideration is a general case of a transient MHD flow in which an initial steady state is subject to a finite amplitude disturbance. The governing equations are described, their finite difference formulation is presented and the FICE algorithm is given. The boundary conditions are treated by classifying them into physical and computational ones. The usefulness of the FICE algorithm is demonstrated using a physical example concerning the dynamical response of the static solar atmosphere due to a representative photospheric disturbance.

Wu, S. T.↗