Water exit dynamics of buoyant spheres

Tadd T. Truscott, Brenden P. Epps, and Randy H. Munns
Phys. Rev. Fluids 1, 074501 – Published 1 November 2016
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Abstract

Buoyant spheres released below the free surface can rise well above the surface in a phenomenon known as pop-up. Contrary to intuition, increasing the release depth sometimes results in a lower pop-up height. We present the pop-up height of rising buoyant spheres over a range of release depths (1–12.5 diameters) and Reynolds numbers (4×104 to 6×105). While the dynamics of rising buoyant spheres and bubbles has been thoroughly investigated for Reynolds numbers below 104, pop-up in these larger-Reynolds-number regimes has not been studied. Yet the underwater motions of the sphere for the Reynolds numbers we study are the key to understanding the pop-up height. Two major regimes are apparent: vertical and oscillatory. The vertical regime exhibits a nearly vertical underwater trajectory and results in the largest pop-up heights. The oscillatory regime exhibits an underwater trajectory with periodic lateral motions and results in lower pop-up heights; this periodic lateral motion is modulated by unsteady vortex shedding in the wake of the sphere. Despite these complex fluid structure interactions, the experiments presented herein yield extremely repeatable results.

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  • Received 21 March 2016

DOI:https://doi.org/10.1103/PhysRevFluids.1.074501

©2016 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Tadd T. Truscott*

  • Department of Mechanical and Aerospace Engineering, Utah State University, Logan, Utah 84322, USA

Brenden P. Epps

  • Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA

Randy H. Munns

  • Department of Mechanical Engineering, Brigham Young University, Provo, Utah 84602, USA

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Issue

Vol. 1, Iss. 7 — November 2016

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