Rf. Folse et Cw. Piker, ANALYSIS OF SPATIAL PATTERNS IN SECONDARY FLOWS GENERATED BY TORSIONALLY OSCILLATING SPHERES IN LINEARLY STRATIFIED FLUIDS, Physics of fluids, 10(1), 1998, pp. 113-118
Measurements have been made of the cellular flow patterns observed by
Folse [Phys. Fluids 6, 537 (1994)] in the secondary flow field of tors
ionally oscillating spheres in stratified fluids. Shadowgraphs were ma
de of the secondary flow field of spheres, radii between 2.52 and 5.08
cm, torsionally oscillating (frequencies in the range 1.0 rad/s less
than or equal to omega less than or equal to 13.5 rad/s and amplitudes
theta(0) less than or equal to 1 rad) in linearly stratified fluids,
with Brunt-Vaisala frequencies between 0.8 rad/s less than or equal to
N less than or equal to 2.1 rad/s. The spatial pattern was determined
by measuring the vertical size, d, and radial position, r, for each c
ell. Dimensionless cell size, d/r, was found to depend on the paramete
rs (omega/N), theta(0), and the angular position on the sphere phi mea
sured from the pole. A correlation of the dimensionless cell size is f
ound, independent of sphere radius, given by: d(n)/(r) over bar(n) = 0
.22(omega/N)theta(0)(2) cot(<(phi)over bar>(n)), where (r) over bar(n)
, and <(phi)over bar>(n), are the average radial and angular positions
of the nth cell. This correlation results in a discrepancy between me
asurements and expectations based on a heuristic energy argument. (C)
1998 American Institute of Physics.