Engineering topics

Dgani, Ruth

Publications and source records attributed to Dgani, Ruth.

3 records

NASA NTRS1994

Radiative shock overstability of finite-sized objects

We investigate the radiative shock overstability for finite-sized objects. We follow the analysis of Chevalier & Imamura (1982), but we take into account the transverse flow of material out of the potshock region. The mass loss from the postshock region stabilizes the flow. As a rough estimate, the shock radiative instability takes place when the shock wave position with no radiative cooling (only mass loss present) is larger than the shock position with no mass loss (only radiative cooling present). For typical conditions of planetary nebulae we find that in order for the shock radiative overstability to occur, the nebular radius should be R approximately less than 10(exp 19) n(sub a)(exp -1) cm, where n(sub alpha) is the total number density of the interstellar medium (in units of cm(exp -3). We give several examples of interacting planetary nebulae in light of this condition.

Dgani, Ruth↗

NASA NTRS1994

The wind of EG Andromedae is not dust driven

The symbiotic star EG Andromedae has recently been the subject of several studies investigating its wind properties. Late-type giants are usually considered to have winds driven by radiation pressure on dust. Indeed, the derived wind velocity for EG Andromedae is consistent with this model. We point out here that there is no appreciable dust opacity in the wind of EG Andromedae using constraints on extinction limits from International Ultraviolet Explorer (IUE) and far infrared fluxes from Infrared Astronomy Satellite (IRAS). An alternate mechanism must operate in this star. We suggest that the wind can be driven by radiation pressure on molecular lines.

Van Buren, Dave↗

NASA NTRS1989

On the stream-accretion disk interaction - Response to increased mass transfer rate

The time-dependent interaction between the stream of mass from the inner Lagrangian point and the accretion disk, resulting from an increasing mass transfer rate is calculated. The calculation is fully three-dimensional, using a pseudoparticle description of the hydrodynamics. It is demonstrated that the results of such calculations, when combined with specific observations, have the potential of both determining essential parameters, such as the viscosity parameter alpha, and can distinguish between different models of dwarf nova eruptions.

Dgani, Ruth↗