We report LES and RANS results of the flow in a return channel. Given the same inflow, the LESs and RANS lead to qualitatively similar but quantitatively different results up to the trailing edge of the deswirl vane and qualitatively different results from the trailing edge to the exit of the return channel. The RANS leads to strong vortical structures downstream of the deswirl guide vane. While these vortical motions are found in the LESs, they are much weaker. As a result, the RANS predicts larger variations of the swirl angle, the azimuthal velocity, and the total pressure in the span direction at the exit of the return channel than the LESs. In addition to LES and RANS in their conventional sense, we also conduct an LES on a RANS grid. By comparing the RANS-grid LES results and the LES results, we show that an LES-quality grid is an essential part of an LES.