# Experimental measurements of forces on loose particle in motion over rough bed under waves using oblique particle image velocimetry

29 Jul 2016-Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 138, Iss: 6, pp 062002

About: This article is published in Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme.The article was published on 2016-07-29. It has received None citations till now. The article focuses on the topics: Particle image velocimetry.

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Brown University

^{1}TL;DR: In this paper, the forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen's equation and the subsequent modified versions that have since appeared.

Abstract: The forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen’s equation and the subsequent modified versions that have since appeared. Forces from the undisturbed flow and the disturbance flow created by the presence of the sphere are treated separately. Proper account is taken of the effect of spatial variations of the undisturbed flow on both forces. In particular the appropriate Faxen correction for unsteady Stokes flow is derived and included as part of the consistent approximation for the equation of motion.

3,130 citations

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TL;DR: In this article, it was shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamline moving in the direction opposite to V.

Abstract: It is shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to the streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamlines moving in the direction opposite to V. Here, a denotes the radius of the sphere, κ the magnitude of the velocity gradient, and μ and v the viscosity and kinematic viscosity, respectively. The relevance of the result to the observations by Segree & Silberberg (1962) of small spheres in Poiseuille flow is discussed briefly. Comments are also made about the problem of a sphere in a parabolic velocity profile and the functional dependence of the lift upon the parameters is obtained.

2,912 citations

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21 Jul 1992

TL;DR: In this article, a review of bottom boundary layer flows including the boundary layer interaction between waves and steady currents is presented, and the concept of eddy viscosity for these flows is discussed in depth because of its relation to sediment diffusivity.

Abstract: This book is intended as a useful handbook for professionals and researchers in the areas of Physical Oceanography, Marine Geology, Coastal Geomorphology and Coastal Engineering and as a text for graduate students in these fields. With its emphasis on boundary layer flow and basic sediment transport modelling, it is meant to help fill the gap between general hydrodynamic texts and descriptive texts on marine and coastal sedimentary processes. The book commences with a review of coastal bottom boundary layer flows including the boundary layer interaction between waves and steady currents. The concept of eddy viscosity for these flows is discussed in depth because of its relation to sediment diffusivity. The quasi-steady processes of sediment transport over flat beds are discussed. Small scale coastal bedforms and the corresponding hydraulic roughness are described. The motion of suspended sand particles is studied in detail with emphasis on the possible suspension maintaining mechanisms in coastal flows. Sediment pickup functions are provided for unsteady flows. A new combined convection-diffusion model is provided for suspended sediment distributions. Different methods of sediment transport model building are presented together with some classical models.

1,311 citations

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TL;DR: The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made.

Abstract: The development of the method of particle image velocimetry (PIV) is traced by describing some of the milestones that have enabled new and/or better measurements to be made. The current status of PIV is summarized, and some goals for future advances are addressed.

1,284 citations

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TL;DR: In this article, a simulation of high-concentration sheet flow transport in oscillatory flows quantifies the effect of fluid acceleration on bed load transport in highly unsteady flows typical of nearshore marine environments.

Abstract: Fully three-dimensional discrete particle computer simulations of high-concentration sheet flow transport in oscillatory flows quantify the effect of fluid acceleration on bed load transport in highly unsteady flows typical of nearshore marine environments. A simple impulse-momentum approach explains simulation results and forms the basis for adding an acceleration-related term to widely used energetics sediment transport formulae. Transport predicted by the acceleration term becomes increasingly significant as wave shape approaches the sawtooth profile characteristic of surf zone bores. Simulations integrate F = ma and a corresponding set of equations for the torques for each sphere. Normal and tangential forces between contacting particles are linear functions of the distance between sphere centers and the relative tangential displacement at the contact point, respectively; particle interactions are both inelastic and frictional. Pressure gradient forces generated by the passage of surface gravity waves drive fluid and particle motion in a stack of thin horizontal fluid layers that exchange momentum and exert fluid drag, added mass, and buoyancy forces on particles. Transport properties of the simulated granular-fluid assemblage are robust to large variations in material properties of the particles. Simulated transport rates agree with available experimental data for unsteady transport of coarse sands; the mode of bed load motion, dispersion of bed load particles, and particle segregation by size and density are qualitatively consistent with available particle-scale observations of bed load transport of natural particles.

334 citations