Velocity gradient

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

Velocity effects on the profiles of Hα and two FeI lines

Abstract: Profiles are computed for Ha and two Fei lines for a differentially moving atmosphere. The results show that the profiles are asymmetric and that velocity measurements made in the Doppler cores will often lead to erroneous results when the velocity gradient is significant in the regions of the atmosphere where the core forms.

Rigorous justification of the Kirchhoff law for junction of thin pipes filled with viscous fluid

Abstract: We study the junction of $m$ pipes that are either thin or long (i.e. they have small ratio between the cross-section and the length, denoted by $\varepsilon $). Pipes are filled with incompressible Newtonian fluid and the values of the pressure $p_i$ at the end of each pipe are prescribed. By rigorous asymptotic analysis, as $\varepsilon\to 0$, we justify the analog of the Kirchhoff law for computing the junction pressure. In interior of each pipe the effective flow is the Poiseuille flow governed by the pressure drop between the end of the pipe and the junction point. The pressure at the junction point is equal to a weighted mean value of the prescribed $p_i$-s (Kirchhoff law). In the vicinity of the junction there is an interior layer, with thickness $\varepsilon\, \mbox{; ; ; ; log}; ; ; ; (1/\varepsilon)$. To get a better approximation and to control the velocity gradient in vicinity of the junction, first order asymptotic approximation has to be corrected by solving the appropriate Leray problem. We prove the asymptotic error estimate for the approximation.

Velocity-gradient paths in coagulation

Abstract: COAGULATION recognized as an important has long procbeen recognized as a important process for the removal of turbidity in surface-water treatment. Early designs of mechanically stirred coagulation basins commonly were based on detention time and peripheral tip velocities of the agitation paddles. However, the inconsistent performance of early units prompted a study by Camp and Stein.1 Their work established a design criterion based upon the concept of defining and specifying the velocity-gradient input during coagulation. According to Eq 1, the effective velocity gradient G can be calculated from the measured paddle speed N in rpm, the torque input T in dyne-cm, the volume V in cu cm, and the viscosity p in g/cm-sec :

Effect of velocity gradient on propagation speed of tribrachial flames in laminar coflow jets

Abstract: The effect of velocity gradient on the propagation speed of tribrachial flame edge has been investigated experimentally in laminar coflow jets for propane fuel. It was observed that the propagation speed of tribrachial flame showed appreciable deviations at various jet velocities in high mixture fraction gradient regime. From the similarity solutions, it was demonstrated that the velocity gradient varied significantly during the flame propagation. To examine the effect of velocity gradient, detail structures of tribrachial flames were investigated from OH LIF images and Abel transformed images of flame luminosity. It was revealed that the tribrachial point was located on the slanted surface of the premixed wing, and this slanted angle was correlated with the velocity gradient along the stoichiometric contour. The temperature field was visualized qualitatively by the Rayleigh scattering image. The propagation speed of tribrachial flame was corrected by considering the direction of flame propagation with the slanted angle and effective heat conduction to upstream. The corrected propagation speed of tribrachial flame was correlated well. Thus, the mixture fraction gradient together with the velocity gradient affected the propagation speed.