1 research outputs found
On bubble clustering and energy spectra in pseudo-turbulence
3D-Particle Tracking (3D-PTV) and Phase Sensitive Constant Temperature
Anemometry in pseudo-turbulence--i.e., flow solely driven by rising bubbles--
were performed to investigate bubble clustering and to obtain the mean bubble
rise velocity, distributions of bubble velocities, and energy spectra at dilute
gas concentrations (%). To characterize the clustering the pair
correlation function was calculated. The deformable bubbles with
equivalent bubble diameter mm were found to cluster within a radial
distance of a few bubble radii with a preferred vertical orientation. This
vertical alignment was present at both small and large scales. For small
distances also some horizontal clustering was found. The large number of
data-points and the non intrusiveness of PTV allowed to obtain well-converged
Probability Density Functions (PDFs) of the bubble velocity. The PDFs had a
non-Gaussian form for all velocity components and intermittency effects could
be observed. The energy spectrum of the liquid velocity fluctuations decayed
with a power law of -3.2, different from the found for
homogeneous isotropic turbulence, but close to the prediction -3 by
\cite{lance} for pseudo-turbulence