ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
2pAO1. Effects of salinity on the acoustics of bubble plumes.
Gregory J. Orris
Naval Res. Lab., Washington, DC 20375
A previous paper [ 2826(A) (1993)] presented acoustic data
collected near bubble plumes of various void fractions and sizes produced by
varying the flow velocity of a water jet impinging normally on a water surface.
Subsequent analysis has revealed that the data's spectral content varies
considerably between the two phases of the experiment---one involving fresh
water in Lake Washington and the other involving salt water in Puget Sound. In
the fresh-water portion of the experiment the spectra are completely dominated
by modes corresponding roughly to the gross dimensions of the plume. In the
salt-water portion of the experiment, the salts and other contaminants (which
act as surfactants and lower the surface tension) dramatically reduce the mean
bubble size with respect to that of fresh water. The acoustic data from the
salt-water experiment are drastically different from that of the fresh water,
and show little or no modal structure. For this particular physical situation
it is suggested that the dominant acoustic generation process is likely to be
turbulence. Furthermore, differences in the acoustic signatures of the
experiment could be exploited to determine, amongst other things, the
concentration of the salts and contaminants.