Abstract
In order to investigate and observe turbulent heat transfer in the entrance region of combined pipe flow, direct numerical simulations (DNS) are carried out. The DNS results show the quantitative statistics of turbulent heat transfer in the pipe flow in detail. In the present DNS, since the pipe is uniformly heated at the wall, both stable and unstable thermal stratifications are formed in the pipe, i.e., the wall temperature is higher than the temperature of inlet fluid. The velocity field is affected by the thermal stratifications, in which the secondary flow clearly appears in the pipe, while the thermal field develops in the entrance region of pipe. The DNS clearly demonstrates distributions of Reynolds shear stress and turbulent heat flux in the entrance region of combined pipe flow.
