Abstract

Motivated by anomalous entrainment behaviour in atmospheric plumes during cloud formation, Bhat and Narasimha (JFM 1996) pioneered an experimental technique to investigate the problem in the laboratory. Hunt (1996) presented an analysis that suggested that a positive forcing would lead to an increase in entrainment, whereas an increase in the relative turbulent intensity would lead to a decrease. However, Bhat and Narasimha concluded that the experimental data did not support Hunt’s proposal. We readdress both the analysis of Hunt and the interpretation of the experimental data, and provide and alternative description of entrainment suitable for this particular flow. With the aid of implicit large eddy simulations (ILES), we investigate the new approach in the context of turbulent jets with off-source heating, and provide evidence that suggests the data from the laboratory experiment are in fact consistent with the essence of Hunt’s proposal.