Development and Evaluation of a Simplified CFD Model for a Swirl Diffuser with the Aid of 2D Particle Image Velocimetry

In numerical modeling of swirl diffusers, simplifying the diffuser geometry can substantially reduce simulation costs. This study describes the development and performance evaluation of simplified computational fluid dynamics (CFD) models of a swirl diffuser by using 2D particle image velocimetry (PIV). Two simplified models were created by replacing the diffuser with simple supply openings, where momentums were prescribed. The first model defined momentums solely based on geometric rules. In the second, it was demonstrated how the accuracy of the first, geometry-based model, can be improved by adjusting the momentums using results from a detailed CFD model. The effect of using the Reynolds stress model or the SST <i>k-ω</i> turbulence model on the accuracy of the CFD model and computation time was investigated. The simplified models were benchmarked against both the detailed CFD model and the PIV measurements. The corrected simplified geometry combined with the SST <i>k-ω</i> turbulence model achieved a favorable balance between reliability and computational efficiency. Although the two-dimensional nature of the PIV measurements presented challenges for three-dimensional CFD validation, they proved valuable for developing and assessing the simplified models.