Termofiziksel gradyenine sahip duvarda düzenli türbülans yapilarinin incelenmesi

Coherent vortical structures have major responsibility for friction losses and heat transfer in wall-bounded turbulent flows, yet the hairpin vortex theory has been well-founded for boundary layer flows in recent decades. However, the modeling of buoyancy-driven turbulent flows has remained challenging, and existing models would poorly predict the effects of buoyancy. Here we show that the hairpin vortices in turbulent buoyancy-driven boundary layer consistently point the upstream direction of flow instead of downstream, and this characteristic is intrinsic vortex behavior for buoyancy-driven flow. We uncover that the coherent vortices straddle high-speed streak instead of low-speed streak; moreover, the quadrant of the tangential Reynolds shear stresses, one of the most important terms for the Reynolds-averaging models, dominates the first and third quadrant instead of the second and fourth one. These findings may help to improve our understanding of buoyancy-driven flow and buoyancy effects in turbulent models. The most important of all, the theory of anti-hairpin vortex is established through the present study.