円管内の複合対流乱流境界層の数値解析

抄録

The object of this study is to investigate and observe characteristics of heat transfer phenomena of turbulent combined-convection boundary layer in a pipe by means of direct numerical simulation (DNS). DNS is carried out under two wall thermal conditions, where the wall of pipe is heated from midstream of field by an isothermal or an isoheat flux condition. On the other hand, the fully-developed velocity boundary layer is given at the inlet of pipe, but the velocity boundary layer is affected by thermal field due to the existence of buoyancy. Thus, a secondary flow and an asymmetrical distribution of velocity field can be observed in the downstream region due to the buoyancy effect. As for the thermal field, distribution of mean temperature and Nusselt number in the entrance region of thermal field are clearly shown by DNS, in which the effect of different of wall thermal condition is also observed. In the downstream region, since the velocity and thermal fields interfere mutually, it can be observed occurrence of complex turbulent heat transfer phenomena. Therefore, DNS reveals characteristics and structures of combined-convection turbulent boundary layer in a pipe.