Numerical computations of steady and unsteady flow in bended pipes

The steady and pulsative turbulent flows in curved pipes have been computed with two different modeling approaches; the Reynolds Averaged Navier-Stokes (RANS) technique and Large Eddy Simulations (LES). The results from computations of the flow in a single bended pipe have been compared to experimental data. The comparisons show poor agreement for the RANS technique at the exit of the bend, while the LES computations show better agreement with the measured velocity profiles. LES in contrast to RANS, can also provide much more details about the dynamics of the flow. It is also shown that small uncertainties in the inlet boundary conditions can result in significant variations in the flow field. Different types of small amplitude secondary flow at the inlet affect the flow downstream of the bend. The approach enables one to state that for the experiments under consideration the lack of data on the secondary flow prevents a direct validation of the LES results. The pulsatile flow in a double bended pipe has also been investigated and the vortex cores are visualized to enable a better insight into the unsteady flow field and the effects of the inflow pulsations. (Less)