Flow separation in a conical diffuser with large divergence angle （29.14°） and large area ratio （3.533） is eliminated by a novel passive flow control device called Karman-Vortex Generator （KVG）. The effect of the KVG is verified and investigated by the URANS, DES and DDES methods based on the SST model. CFD results show that the performance coefficient of the diffuser can be doubled by the KVG, and the total pressure recovery coefficient can be improved by about 1.2%. DES and DDES re- suits show that the KVG can introduce a Karman-vortex street frequency in the diffuser. This frequency decays rapidly, and could not be detected in the ending plane of the expansion section, Different KVG configurations with different locations and dimensions are numerically simulated and compared. Some suggestions are provided.
