Direct numerical simulations were performed to investigate the dissimilarity between heat and momentum transfer of the developing turbulent spot in a plane Couette flow under thermal stratification. The turbulent spots were generated by a single pair of eddies in the laminar flow with a Reynolds number of 450 and a Prandtl number of unity. As a result, during the development of the turbulent spot, it was found that an efficient heat transport state, where heat transport exceeds the momentum transport, was realized in both stable and unstable thermal stratification conditions. The stable stratification tends to extend the turbulent transition term, resulting in the longer efficient heat transport state period.
Nozawa et al. (Wed,) studied this question.