Flame length measurements of the turbulent plume

A steady source of buoyancy creates a plume. Experi­ mental and theoretical studies of plumes have been mainly concerned with the far-field (self-similar) velocity and den­ sity profiles. •-3 Yet in many practical situations, knowledge regarding the rate of molecular scale mixing of the buoyant fluid with its environment is needed. This is especially true in the context of atmospheric studies, where models for' the formation and growth stages of clouds utilize the turbulent plume dynamics. In this Letter a simple argument for mixing in plumes is presented and its implications are examined in light of the experimental findings. A global measure of plume entrainment E is the ratio of axial volume flux Qat any station to the initial volume flux Q0 at the source. Rouse, Yih, and Humphreys 1 reported the mean plume volume flux in the self-similar region to be