Interscale/Interspace Energy Transfers at the Turbulent/Non-turbulent Interface

Turbulent dissipation results from interscale/cascade interactions across a wide range of turbulence scales and plays a central role in turbulent shear flow development, such as jet growth rate. In this study, we investigate interscale and interspace energy transfer mechanisms at the turbulent/non-turbulent interface (TNTI) in a temporally developing turbulent jet using data from our own direct numerical simulations. The TNTI is a very sharp interface at the edge of the jet which marks the dynamic border between rotational and irrotational flow regions. We follow the method based on the Karman-Howard-Monin-Hill equation initiated by Zhou & Vassilicos (2020) and calculate interscale and interspace energy transport rates at the TNTI, however unlike them we do it conditionally on interface characteristics such as TNTI position relative to the centreline, orientation, curvature and/or local propagation speed relative to the fluid. Curvature and folds are expected to play an important role on entrainment, TNTI propagation and longevity which, in turn, depend on interscale and interspace energy transfers at the TNTI's vicinity. In this study, we try to draw the link between the structure and evolution of the TNTI and the interscale/interspace energy transfer mechanisms.