Abstract
It has been observed by many authors that for ascending bubbly flows, the gas fraction distributes radially
in different manners. Depending on the flow conditions and channel characteristics, the bubbles may
accumulate in the center of the pipe (core peak) or near the walls (wall peak). The radial distribution of
gas fraction significantly affects the friction coefficient and the heat transfer. Therefore, it is important to
be able to predict which distribution will appear under certain flow conditions. In this note, by analyzing
a vast experimental data base, a criterion to identify the transition from core to wall peak is proposed. The
transition occurs when both Reynolds and Weber numbers reach critical values (Rcrit = 1500, Wcrit = 8).
This criterion is validated with our experimental results and with those found in the literature.