Abstract:
Experimental results are presented for the spreading of buoyant drops
and gravity currents beneath or at a free surface, respectively. The
spreading occurs at low Reynolds number, and no interfacial tension
exists between the spreading drop or current and the ambient fluid. As
the ratio of the spreading and ambient fluid viscosities, \lambda,
is varied with respect to the aspect ratio of the drop or current,
R/a, spreading rates in the three regimes \lambda <<
[ln(R/a)]^-1 a/R, a/R >> \lambda << R/a, and \lambda >> R/a
are considered. Experimental spreading rates in these three
viscosity-ratio regimes show agreement with the theoretical solutions
for long-term spreading.