Topic
Velocity gradient
About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, a trapezoidal geometry of the asymmetrical flow field-flow fractionation (FFF) channel is introduced to regulate the longitudinal flow velocity, where the breadth decreases on going toward the channel outlet, making it possible to level out the steep linear velocity gradients in the rectangular channels.
Abstract: A new trapezoidal geometry of the asymmetrical flow field-flow fractionation (FFF) channel introduces an additional means to regulate the longitudinal flow velocity. The trapezoidal geometry, where the breadth decreases on going toward the channel outlet, makes it possible to level out the steep linear velocity gradients that can appear in the rectangular channels. Equations for the channel flow velocity gradient and the void time are derived
149 citations
TL;DR: In this paper, the authors compared single-phase and two-phase models to predict convective heat transfer coefficient and friction factor at the entry region of uniformly heated pipe, and found that the simulation results showed that the Eulerian-Eulerian model can reduce the computational cost by up to 50% in terms of accuracy and computational cost.
147 citations
TL;DR: In this article, it was found that fibrous crystallization of polyethylene melt appeared to occur preferentially along this axis, implying that longitudinal velocity gradients played an important part in the production of this fibrous material.
144 citations
TL;DR: In this paper, a study of dense molecular gas kinematics in 17 nearby protostellar systems using single-dish and interferometric molecular line observations is presented, where the velocity fields observed on large and small scales are more complex than would be expected from rotation alone, suggesting that complex envelope structure enables other dynamical processes (i.e., infall) to affect the velocity field.
Abstract: We present a study of dense molecular gas kinematics in 17 nearby protostellar systems using single-dish and interferometric molecular line observations. The non-axisymmetric envelopes around a sample of Class 0/I protostars were mapped in the N2H+ (J = 1 → 0) tracer with the IRAM 30 m, CARMA, and Plateau de Bure Interferometer, as well as NH3 (1,1) with the Very Large Array. The molecular line emission is used to construct line-center velocity and linewidth maps for all sources to examine the kinematic structure in the envelopes on spatial scales from 0.1 pc to ~1000 AU. The direction of the large-scale velocity gradients from single-dish mapping is within 45° of normal to the outflow axis in more than half the sample. Furthermore, the velocity gradients are often quite substantial, the average being ~2.3 km s–1 pc–1. The interferometric data often reveal small-scale velocity structure, departing from the more gradual large-scale velocity gradients. In some cases, this likely indicates accelerating infall and/or rotational spin-up in the inner envelope; the median velocity gradient from the interferometric data is ~10.7 km s–1 pc–1. In two systems, we detect high-velocity HCO+ (J = 1 → 0) emission inside the highest-velocity N2H+ emission. This enables us to study the infall and rotation close to the disk and estimate the central object masses. The velocity fields observed on large and small scales are more complex than would be expected from rotation alone, suggesting that complex envelope structure enables other dynamical processes (i.e., infall) to affect the velocity field.
144 citations
TL;DR: In this paper, the radial migration of rigid spheres, rods, and discs and deformable fluid drops was studied in oscillatory and pulsatile flow over a range of the alpha parameter from 2 to 20 and at particle to tube diameter ratios ranging from 0.04 to 0.1.
143 citations