Engineering topics

Giuliani, J. L., Jr.

Publications and source records attributed to Giuliani, J. L., Jr..

4 records

NASA NTRS1986

Numerical simulations of comets - Predictions for Comet Giacobini-Zinner

Simulations of Comet Giacobini-Zinner's interaction with solar wind are described and results are presented. The simulations are carried out via the numerical solution of the ideal MHD equations as an initial value problem in a uniform solar wind. The calculations are performed on a Cartesian mesh centered at the comet. Results reveal that the first significant modifications of the solar wind along the ISEE/ICE trajectory will occur 100,000 km from the solar wind comet axis.

Fedder, J. A.↗

NASA NTRS1984

Thermal evaporation of spherical clouds - Effects of viscous stresses

The thermal evaporation of a cold spherical cloud embedded in hot gas is analyzed, including the effects of viscous stresses as well as 'saturation' of the conductive heat flux, for the case of equal electron and ion temperatures. The relevant transport properties for an H-He plasma are discussed, including the modification of these transport coefficients when temperature or velocity gradients become large. The fluid-dynamical equations for steady spherical evaporation are given and cast into dimensinless form. Numerical integration of these equations and the results are discussed, emphasizing the novel features of the viscous solutions, astrophysical implications, and uncertainties in the physics.

Giuliani, J. L., Jr.↗

NASA NTRS1984

On the dynamics in evaporating cloud envelopes

Cowie and McKee (1977) have conducted an analytical study of the case of an isolated, spherical cloud at rest in an infinite, hot medium. The present investigation is concerned with the theoretical model considered by Cowie and McKee for a thermally evaporating cloud. An analysis is conducted under the same conditions of inviscid flow with temperature equipartition. The current analysis allows for a continuous change in the saturation of the conductivity, rather than abrupt transitions from a classical to a fully saturated regime and back again, as in the model employed by Cowie and McKee. By suitable variable transformations, the momentum and energy equations can be reduced in the inviscid limit to a single equation for the Mach number in terms of a modified radius, and the solutions represented in a phase plane. An analytic model for the structure of the shock layer is developed.

Giuliani, J. L., Jr.↗

NASA NTRS1983

Mass loss from evolved stars. II - Radio continuum emission and evolution to planetary nebulae

The radio continuum properties of cool evolved stars are investigated from the viewpoint of mass loss mechanisms and evolution through the planetary nebula stage. The VLA was used to search 32 high mass loss rate objects for 6-cm continuum emission, leading to the detection of NGC 7027, CRL 618, R Aqr, IRC + 10216, and Omicron Ceti. The evolution of such objects to the planetary nebula stage was studied by calculating the propagation of an ionization front into the remnant neutral envelope that is produced by continuous mass loss in the red giant stage. It is found that none of the stars has a hot, compact companion, except for the known cases of R Aqr and Mira, and that envelope fractional ionization is in most cases as small as less than about 0.001.

Spergel, D. N.↗