The emergence of bubbleinduced scaling in thermal spectra in turbulence
Abstract
We report on the modification of the spectrum of a passive scalar inside a turbulent flow by the injection of large bubbles. Although the spectral modification through bubbles is well known and well analysed for the velocity fluctuations, little is known on how bubbles change the fluctuations of an approximately passive scalar, in our case temperature. Here we uncover the thermal spectral scaling behaviour of a turbulent multiphase thermal mixing layer. The development of a $3$ spectral scaling is triggered. By injecting large bubbles ( ${Re}_{{bub}} = {O}(10^2)$ ) with gas volume fractions $\alpha$ up to 5 %. For these bubbly flows, the $5/3$ scaling is still observed at intermediate frequencies for low $\alpha$ but becomes less pronounced when $\alpha$ further increases and it is followed by a steeper $3$ slope for larger frequencies. This $3$ scaling range extends with increasing gas volume fraction. The $3$ scaling exponent coincides with the typical energy spectral scaling for the velocity fluctuations in highReynoldsnumber bubbly flows. We identify the frequency scale of the transition from the $5/3$ scaling to the $3$ scaling and show how it depends on the gas volume fraction.
 Publication:

Journal of Fluid Mechanics
 Pub Date:
 March 2023
 DOI:
 10.1017/jfm.2023.66
 arXiv:
 arXiv:2207.05175
 Bibcode:
 2023JFM...958A...5D
 Keywords:

 Physics  Fluid Dynamics
 EPrint:
 doi:10.1017/jfm.2023.66