Velocity gradient

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

Influence of a velocity gradient on small angle neutron scattering of a sheared solution with rodlike micelles

Abstract: A solution consisting of 20 mM cetylpyridiniumsalicylate (CPS) and 20 mM sodiumsalicylate (NaSal) in which rodlike micelles are present, was sheared and studied in a small angle neutron scattering (SANS) experiment. Without a velocity gradient the scattering curves of constant intensity were circles which reflect an isotropic distribution of the orientation of the scatterers. If a velocity gradient is applied to the solution the curves of constant scattering intensity show a characteristic deviation from the circles due to the partially ordering of the rods. From that deviation the rotational diffusion coefficient can be obtained. A theoretical treatment of this problem is given and applied to the experimental data.

Entropy Generation Analysis of Open Parallel Microchannels Embedded Within a Permeable Continuous Moving Surface: Application to Magnetohydrodynamics (MHD)

Abstract: This paper presents a new design of open parallel microchannels embedded within a permeable continuous moving surface due to reduction of exergy losses in magnetohydrodynamic (MHD) flow at a prescribed surface temperature (PST). The entropy generation number is formulated by an integral of the local rate of entropy generation along the width of the surface based on an equal number of microchannels and no-slip gaps interspersed between those microchannels. The velocity, the temperature, the velocity gradient and the temperature gradient adjacent to the wall are substituted into this equation resulting from the momentum and energy equations obtained numerically by an explicit Runge-Kutta (4, 5) formula, the Dormand-Prince pair and shooting method. The entropy generation number, as well as the Bejan number, for various values of the involved parameters of the problem are also presented and discussed in detail.

Analytical solution of velocity distribution for flow through submerged large deflection flexible vegetation

Abstract: An analytical solution for predicting the vertical distribution of streamwise mean velocity in an open channel flow with submerged flexible vegetation is proposed when large bending occurs. The flow regime is separated into two horizontal layers: a vegetation layer and a free water layer. In the vegetation layer, a mechanical analysis for the flexible vegetation is conducted, and an approximately linear relationship between the drag force of bending vegetation and the streamwise mean flow velocity is observed in the case of large deflection, which differes significantly from the case of rigid upright vegetation. Based on the theoretical analysis, a linear streamwise drag force-mean flow velocity expression in the momentum equation is derived, and an analytical solution is obtained. For the free water layer, a new expression is presented, replacing the traditional logarithmic velocity distribution, to obtain a zero velocity gradient at the water surface. Finally, the analytical predictions are compared with published experimental data, and the good agreement demonstrates that this model is effective for the open channel flow through the large deflection flexible vegetation.