Rib이 설치된 파이프 유동에서의 난류물질전달의 큰 에디 모사

초록

Understanding heat/mass transfer mechanisms in turbulent flow is essential for solving many engineering problems. From the view point of heat/mass transfer control, surface roughness is popular for enhancing heat/mass transfer in turbulent pipe flow, relevant to heat exchangers, mixers, and nuclear reactors to name a few. Such a surface roughness is often modeled with a rib. In the current investigation, Large eddy simulation with a dynamic subgrid-scale model implemented has been carried out for the pipe flow with periodically-mounted ribs to elucidate the characteristics of turbulent mass transfer. The Reynolds number considered here is ReD=24,000 based on the pipe diameter (D) and the mean bulk velocity (Ub), and the Schmidt number (Sc) is 0.71. The ratio of the rib height (k) to the pipe radius is 0.125, and the pitch ratio (p/k) is 18, compatible with the geometrical configuration of Baughn and Roby (1992). The profiles of mean velocity components, mean concentration, root-mean-squares (rms) of concentration fluctuations are presented at the selected streamwise locations downstream of a rib. In comparison with the straight-pipe case at the same Re and Sc, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent mass transfer. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the mass-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering.