The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

César Rosales - One of the best experts on this subject based on the ideXlab platform.

Sunny Chiuwebster - One of the best experts on this subject based on the ideXlab platform.

  • stability of a dragged viscous thread onset of stitching in a fluid mechanical sewing machine
    Physics of Fluids, 2006
    Co-Authors: Neil M Ribe, John R Lister, Sunny Chiuwebster
    Abstract:

    A thin thread of viscous fluid that falls on a moving belt acts like a fluid-mechanical “sewing machine,” exhibiting a rich variety of “stitch” patterns including meanders, translated coiling, slanted loops, braiding, figures-of-eight, W-patterns, side kicks, and period-doubled patterns. Using a numerical linear stability analysis, we determine the critical belt speed and oscillation frequency of the first bifurcation, at which a steady dragged viscous thread becomes unstable to transverse oscillations or “meandering.” The predictions of the stability analysis agree closely with the experimental measurements of Chiu-Webster and Lister [J. Fluid Mech. 569, 89 (2006)]. Moreover, the critical belt speed and onset frequency for meandering are nearly identical to the contact-point migration speed and angular frequency, respectively, of steady coiling of a viscous thread on a Stationary Surface, implying a remarkable degree of dynamical similarity between the two phenomena.

  • the fall of a viscous thread onto a moving Surface a fluid mechanical sewing machine
    Journal of Fluid Mechanics, 2006
    Co-Authors: Sunny Chiuwebster, John R Lister
    Abstract:

    A viscous thread falling onto a steadily moving horizontal belt shows a surprisingly complex range of behaviour in experiments. Low belt speeds produce coiling, as might be expected from the behaviour of a thread falling onto a Stationary Surface. High belt speeds produce a steady thread, whose shape is predicted well by theory developed to describe a stretching viscous catenary with Surface tension and inertia. Intermediate belt speeds show several novel modes of oscillation, which lay down a wide variety of patterns on the belt. The patterns include meanders, side kicks, slanted loops, braiding, figures-of-eight, Ws, and also period-doubled versions of figures-of-eight, meanders and coiling. The experimental boundary between steady and unsteady behaviour occurs at a slightly lower belt speed than the loss of the steady solution for a stretching catenary.

John R Lister - One of the best experts on this subject based on the ideXlab platform.

  • stability of a dragged viscous thread onset of stitching in a fluid mechanical sewing machine
    Physics of Fluids, 2006
    Co-Authors: Neil M Ribe, John R Lister, Sunny Chiuwebster
    Abstract:

    A thin thread of viscous fluid that falls on a moving belt acts like a fluid-mechanical “sewing machine,” exhibiting a rich variety of “stitch” patterns including meanders, translated coiling, slanted loops, braiding, figures-of-eight, W-patterns, side kicks, and period-doubled patterns. Using a numerical linear stability analysis, we determine the critical belt speed and oscillation frequency of the first bifurcation, at which a steady dragged viscous thread becomes unstable to transverse oscillations or “meandering.” The predictions of the stability analysis agree closely with the experimental measurements of Chiu-Webster and Lister [J. Fluid Mech. 569, 89 (2006)]. Moreover, the critical belt speed and onset frequency for meandering are nearly identical to the contact-point migration speed and angular frequency, respectively, of steady coiling of a viscous thread on a Stationary Surface, implying a remarkable degree of dynamical similarity between the two phenomena.

  • the fall of a viscous thread onto a moving Surface a fluid mechanical sewing machine
    Journal of Fluid Mechanics, 2006
    Co-Authors: Sunny Chiuwebster, John R Lister
    Abstract:

    A viscous thread falling onto a steadily moving horizontal belt shows a surprisingly complex range of behaviour in experiments. Low belt speeds produce coiling, as might be expected from the behaviour of a thread falling onto a Stationary Surface. High belt speeds produce a steady thread, whose shape is predicted well by theory developed to describe a stretching viscous catenary with Surface tension and inertia. Intermediate belt speeds show several novel modes of oscillation, which lay down a wide variety of patterns on the belt. The patterns include meanders, side kicks, slanted loops, braiding, figures-of-eight, Ws, and also period-doubled versions of figures-of-eight, meanders and coiling. The experimental boundary between steady and unsteady behaviour occurs at a slightly lower belt speed than the loss of the steady solution for a stretching catenary.

Ana Hurtado - One of the best experts on this subject based on the ideXlab platform.

Farshid Sadeghi - One of the best experts on this subject based on the ideXlab platform.

  • The Effects of a Stationary Surface Pocket on EHL Line Contact Start-Up
    Journal of Tribology, 2004
    Co-Authors: Jiaxin Zhao, Farshid Sadeghi
    Abstract:

    In this paper, the start-up process of line contact elastohydrodynamic lubrication with a Stationary central Surface pocket is studied. The solution of the pressure profile and film thickness distribution in the contact area is achieved by using a mixed lubricated-solid contact model. The mass balance of pocket lubricant flow is enforced by using a simple algorithm which adjusts the pocket cavitation boundary. With the Surface pocket in the center of contact, the Hertzian contact area is divided into two micro-EHL contacts: the inlet micro-EHL contact and the outlet micro-EHL contact. The amount of lubricant trapped inside the pocket determines the overall start-up behavior If the lubricant trapped is less than a critical amount, the two micro-EHL contact would be in start-up condition in serial the lubricant film builds up in the inlet micro-EHL contact area first and then the lubricant film builds up in the outlet micro-EHL contact after the inlet lubricant flow fills the pocket. The start-up time in this case is longer than the start-up time for smooth Surface start-up. If the lubricant trapped is more than the critical amount, the two micro-EHL contact would be in start-up condition in parallel: a lubricant film builds up in the inlet micro-EHL contact and at the same time a lubricant film builds up in the outlet micro-EHL contact. The start-up time in this case is much smaller than that of the smooth Surface start-up. Compared with the smooth Surface start-up condition, because the solid contact vanishes faster, there would be less frictional heat generated in the contact area and thus the Surface temperature rise during the start-up process would be much smaller. These effects could prove beneficial in applications with frequent start and stop or oscillating running conditions, in which direct solid to solid contact occurs at the start (restart) of motion.

  • A Comparison of the Fluid Models Effect on the Internal Stresses of Rough Surfaces
    Journal of Tribology, 1991
    Co-Authors: Farshid Sadeghi
    Abstract:

    A comparison between the effects of Newtonian, hyperbolic, and Eyring fluid models on the internal stresses in EHD lubrication of a smooth and rough Stationary Surface in contact with a moving smooth Surface was obtained. The elasticity equation was modified with the experimental Surface measurements obtained from a typical bearing