Relationship between velocity and thermal fields in adverse-pressure-gradient turbulent boundary layer

摘要

Characteristics of turbulent boundary layer flows with adverse pressure gradients (APG) differ significantly from those of canonical boundary layers. We have investigated the effects of APG on the velocity and temperature fluctuations in a thermal boundary layer developing on the uniformly heated plate. It is found that, in the APG boundary layer, the turbulent Prandtl number decreases in the outer layer. This is due to that in APG flow the eddy diffusivity for momentum decreases rapidly, though the corresponding thermal diffusivity changes quite slightly. Moreover, the quadrant splitting analysis reveals that the ejection motions whose durations become larger in the APG flow contribute significantly to the heat transport, whereas the sweep motions whose durations become shorter are the main contributors to the momentum transfer.