Velocity gradient

About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.

Reflection and absorption of ion-acoustic waves in a density gradient

Abstract: One problem with ion‐acoustic waves is that sometimes they are observed to be reflected from discharge tube walls, and sometimes to be absorbed. Theoretical computation reveals that a velocity gradient produced by a density gradient plays a significant role in the reflection. The velocity gradient produces a subsonic−supersonic transition and long wavelength waves are reflected before reaching the transition while short wavelength waves penetrate over the transition and are absorbed in the supersonic flow plasma.

Velocity Gradient Stabilised, Continuous, Free Flow Electrophoresis. A Review

Abstract: A new technique for continuous preparative electrophoresis based on the concept of J. St.L. Philpot1 is described, in which electrophoresis is carried out in free solution in an annulus, the voltage gradient being perpendicular to the direction of flow. Stable annular flow is maintained by a gradient of angular velocity created by rotation of the outer wall of the annulus while the inner wall is held stationary.

Constraints on Intracluster Gas Bulk Motions in Clusters of Galaxies with ASCA

Abstract: The recent detection of Doppler shifts of X-ray spectral lines in the intracluster gas of the Centaurus and Perseus clusters of galaxies with ASCA has raised the question of the frequency of such velocity gradients and their relation to other cluster properties. To address this and improve the sample of ICM velocity gradient candidates we carried out a systematic search of the ASCA archive for clusters with suitable observing conditions that allow full azimuthal mapping of gas velocities near the central regions. Here we present the results of the azimuthal velocity distribution of a sample consisting of the "best" observed clusters for velocity analysis. Our sample encompasses clusters with different physical and morphological characteristics, including both well-behaved "cooling flow" and dynamically active clusters. The gas temperatures of the clusters in our sample range from 1.4 to 6.3 keV. We find velocity substructures in ~15% of the clusters in our sample on the order of a few ×103 km s-1. The significance of the velocity gradients' is greater than 99% in Abell 576 and RX J0419.6+0225, the clusters where velocity gradients are most significant. The velocity gradients are consistent with transitory and/or rotational bulk motion. The velocity gradients in these clusters are unlikely to be due to projected temperature anisotropies, ASCA PSF, intrachip gain variations, and flux contamination from other sources. Chandra images of these clusters do not show obvious cluster alignments within the field of view covered by ASCA. We also noticed a high frequency (~50%) of anisotropic temperature gradients in the core of "cooling flow" clusters, suggesting the presence of frequent dynamical activity in the core of galaxy clusters.