Topic
Velocity gradient
About: Velocity gradient is a research topic. Over the lifetime, 3013 publications have been published within this topic receiving 77120 citations.
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TL;DR: In this article, the motions of single rigid spheres, rods, and discs, and of fluid drops suspended in liquids undergoing Poiseuille flow have been studied, with the exception of effects due to interaction with the wall and neglect of particle size, provided that the equivalent axis ratio re was used instead of the particle axis ratio rp.
285 citations
TL;DR: In this paper, a constitutive equation for the nematic liquid crystals under weak velocity gradient is derived from the kinetic equation presented by Doi, which is consistent with the phenomenological equation proposed by Ericksen and Leslie.
Abstract: Constitutive equation for the nematic liquid crystals under weak velocity gradient is derived from the kinetic equation presented by Doi. The constitutive equation is consistent with the phenomenological equation proposed by Ericksen and Leslie. The six viscosity parameters (Leslie coefficients) appearing in the phenomenological theory are expressed by the molecular parameters.
283 citations
TL;DR: In this paper, the types of potential flows necessary for similar solutions to the boundary-layer equations have been determined for two-dimensional and three-dimensional non-Newtonian fluids.
Abstract: Two- and three-dimensional boundary-layer equations have been developed for pseudoplastic non-Newtonian fluids which can be characterized by a power-law relationship between shear stress and velocity gradient. The types of potential flows necessary for similar solutions to the boundary-layer equations have been determined. For two-dimensional flow the results are similar to those obtained for Newtonian fluids. For three-dimensional flow, however, the possibility of similar solutions depends on the nature of the expression which describes effective viscosity of the fluid. At most, similar solutions are possible only for the case of flow past a flat plate where the potential velocity vector is not perpendicular to the leading edge of the plate; this is a much more restrictive condition than is obtained for Newtonian fluids.
280 citations
TL;DR: In this paper, the authors reveal the inherent relation between the filed synergy principle and the three existing mechanisms for enhancing single phase convective heat transfer, i.e., decreasing of thermal boundary layer, increasing of flow interruption and increasing of velocity gradient near a solid wall, all lead to the reduction of intersection angle between velocity and temperature gradient.
280 citations
TL;DR: In this article, topological features of the velocity gradient field of turbulent channel flow have been investigated using results from a direct numerical simulation for which the Reynolds number based on the channel halfwidth and the centreline velocity was 7860.
Abstract: An investigation of topological features of the velocity gradient field of turbulent channel flow has been carried out using results from a direct numerical simulation for which the Reynolds number based on the channel half-width and the centreline velocity was 7860. Plots of the joint probability density functions of the invariants of the rate of strain and velocity gradient tensors indicated that away from the wall region, the fine-scale motions in the flow have many characteristics in common with a variety of other turbulent and transitional flows: the intermediate principal strain rate tended to be positive at sites of high viscous dissipation of kinetic energy, while the invariants of the velocity gradient tensor showed that a preference existed for stable focus/stretching and unstable node/saddle/saddle topologies. Visualization of regions in the flow with stable focus/stretching topologies revealed arrays of discrete downstream-leaning flow structures which originated near the wall and penetrated into the outer region of the flow. In all regions of the flow, there was a strong preference for the vorticity to be aligned with the intermediate principal strain rate direction, with the effect increasing near the walls in response to boundary conditions.
279 citations