On bubble clustering and energy spectra in pseudoturbulence
Abstract
3DParticle Tracking (3DPTV) and Phase Sensitive Constant Temperature Anemometry in pseudoturbulencei.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 ($\alpha \leq2.2$%). To characterize the clustering the pair correlation function $G(r,\theta)$ was calculated. The deformable bubbles with equivalent bubble diameter $d_b=45$ 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 datapoints and the non intrusiveness of PTV allowed to obtain wellconverged Probability Density Functions (PDFs) of the bubble velocity. The PDFs had a nonGaussian 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 $\approx 5/3$ found for homogeneous isotropic turbulence, but close to the prediction 3 by \cite{lance} for pseudoturbulence.
 Publication:

Journal of Fluid Mechanics
 Pub Date:
 March 2010
 DOI:
 10.1017/S0022112009993570
 arXiv:
 arXiv:0912.1620
 Bibcode:
 2010JFM...650..287M
 Keywords:

 Physics  Fluid Dynamics
 EPrint:
 J. Fluid Mech. 650, 287 (2010)