Abstract：When Reynold-averaged Navier-Stokes(RANS)method is applied to simulate flow fields under the action of centrifugal force, it can fail to sufficient accuracy. Thus, hybrid RANS/LES(large eddy simulation)method(LES)is proposed to improve the accuracy, where RANS is for modelling flow near a wall and LES is for simulating flow behaviour far away from the wall. In this paper, two kinds of RANS/LES models, such as DDES and SAS, were selected to simulate the flow field in a 90° square section curved duct where the action of centrifugal force is dominant to fully understand effects of the force on flow field information such as flow velocity profile, pressure distribution and flow structure in the elbow. The predicted circumferential velocity profiles in cross-sections and the longitudinal distributions of pressure coefficient on the concave surface were compared with the experimental results. Furthermore, the instantaneous flow structure and turbulent kinetic energy distributions were contrasted between two models. It is showed that the velocity profiles and pressure coefficient curves predicted with DDES is similar to those with SAS, however, the results near the wall with the former are even closer to the measurement than with the latter. In terms of the scale distribution of small eddies near the wall, DDES can obtain multiscale small eddies close to the wall, while SAS can capture irregular small eddies adherent to the wall only. For the turbulent kinetic energy field, DDES can represent the low turbulent kinetic energy region at the intersection of four vortices predicted theoretically, but SAS fails to obtain this phenomenon.
