[en] Two models for collisional drift-wave turbulence are studied numerically. First, an electrostatic collisional model is considered, the Hasegawa-Wakatani system. Density and the potential fluctuations are cross-coupled by resistive dissipation, proportional to the adiabaticity parameter C, which determines the character of the system. The transfer of energy is computed and is shown to be same in all regimes, with a local dual cascade dynamics. The second model is an extension of the Hasegawa-Wakatani including the magnetic fluctuations. The influence of the magnetic fluctuations in each regime is studied. The main effect of the magnetic fluctuations is the magnetic induction in the parallel force, which diminishes the adiabaticity of the system by reducing the immediacy of the dissipative coupling between the density and electrostatic fluctuations. The transport is found to be dominantly electrostatic. (author). 5 refs

[en] Helical rf-fields with appropriate wave numbers can be used to exploit for heating purposes the existence within the plasma of the MHD-singular surfaces where the scalar product Kvector.B₀vector=0. In this way the TTMP heating rate can exceed the non-resonant value by a factor of order 1/β and the working frequency ω approximately equal to (the scalar product Kvector.B₀/B₀)Vsub(ti) can in principle be choosen arbitrarily low (but preferentially ω>=nu sub(coll)

[en] The acoustic characteristics of the KSR-III combustion chamber, which experienced combustion instability in its early stages of development, have been investigated. In addition, the tuning characteristics of the applied cavities used to control the combustion instability were studied. To find the optimal tuning conditions, a quantitative study on the performance of an acoustic cavity was conducted by introducing acoustic impedance through a proven 3-D linear acoustic analysis method. Finally, the thermodynamic properties inside the cavity, which are known to be difficult to determine, were investigated, and failure cases of a KSR-III combustor with cavities were investigated using the results from this study. A feasibility case study was conducted to evaluate the stabilization of the combustors using an acoustic cavity, and the results are expected to contribute to the validation process of an acoustic cavity design.

[en] We show that a recently proposed pressure model of collisionless heating in capacitive rf discharges predicts that a small magnetic field (∼10 G) applied transverse to the electric field will induce a heating mode transition from a pressure-heating dominated state to an Ohmic-heating dominated state. This prediction is confirmed by kinetic simulations and experiments. copyright 1996 The American Physical Society

No abstract available

No abstract available

[en] This paper considers the role of acoustic impedance, flow resistance, configuration and geometrical dimensions of regenerators on the power produced in travelling-wave thermoacoustic engines. The effects are modelled assuming a pure travelling-wave and ideal gas, which allows defining a pair of dimensionless factors based on the 'net' acoustic power production. Based on the analysis provided, the acoustic power flow in the regenerators is investigated numerically. It is shown that impedance essentially reflects the proportion between the acoustic power produced from heat energy through the thermoacoustic processes and the acoustic power dissipated by viscous and thermal-relaxation effects in the regenerators. Viscous resistance of the regenerator mainly determines the magnitude of the volumetric velocity and then affects the magnitude of acoustic impedance. High impedance and high volumetric velocity are both required in the regenerators for high power engines. The results also show that the optimum transverse dimension of the gas passage exists, but depends on the local acoustic impedance. In principle, it is possible to obtain an optimum combination between these two parameters.

[en] To assess the significance for galaxy morphological evolution of rapid tidal encounters in dense galaxy cluster cores, we have performed a direct N-body simultion of the passage of a flat disk galaxy through the core of a cD cluster. The disk galaxy is modeled by 100 softened point stars which rotate in the spherical potential of a stablizing Plummer halo. Ambient cluster galaxies are modeled by Plummer spheres. The collisions resulting from a single cluster traversal are found to inflict serious disruption in the outer galaxy disk (r> or approx. =15 kpc), but leave the galaxy nuclear regions essentially unperturbed. If the disks of spiral galaxies form by accretion from extended gaseous envelopes (rapprox.50 kpc) over long time scales (approx.few x 10⁹ years), such rapid tidal encounters may arrest disk development through the disruption and dissipation of the envelope

No abstract available

No abstract available