The steady and transient motion of a sphere through a viscoelastic fluid

Book · Sat Dec 31 04:00:00 EST 1994

OSTI ID:94474

Arigo, M T; McKinley, G H ^[1]

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1. Harvard Univ., Cambridge, MA (United States). Division of Applied Sciences

The settling motion of a sphere along the centerline of a cylindrical tube filled with a viscoelastic fluid is examined experimentally to quantify both the initial transient acceleration from rest and the ultimate steady state motion. A digital imaging system is used to determine the initial transient behavior of the sphere, and a laser Doppler velocimetry (LDV) system is used to independently measure the velocity of the fluid along the centerline of the cylinder as the sphere falls at its ultimate settling velocity. The motion of the sphere is a sensitive function of the dimensionless ratio of the sphere to tube radii a/R and the dimensionless parameter called the Deborah number De. In this study, the authors extend the previous work of Becker et al. (1994), who examined a single ratio of a/R = 0.243, by considering a smaller aspect ratio of a/R = 0.121. Deborah numbers in the range 0.767 {le} De {le} 8.366 were obtained and experimental results who transient velocity over shoots of up to fifty percent of the final constant settling velocity at high De. comparison of the steady state velocity of the sphere in a non-Newtonian fluid to the theoretically-predicted stokes settling velocity reveals an initial drag reduction for low values of De followed by a drag enhancement at high De. LDV measurements in the viscoelastic fluid for both aspect ratios indicate a flow field in which the fore/aft symmetry is broken with the velocity profile in the wake of the sphere extending up to 50 radii behind the sphere at high De.

• OSTI ID: 94474
• Report Number(s): CONF-940659--; ISBN 0-7918-1377-6
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
DRAG
EXPERIMENTAL DATA
FLOW VISUALIZATION
FLUID MECHANICS
FLUIDS
MOTION
RHEOLOGY
SHEAR
SPHERES
STAGNATION
VISCOSITY