CFD-Based Comparative Assessment of RANS Turbulence Model Under Inlet Angle Variation in Ranque-Hilsch Vortex Tube

Abstract

This study conducts a systematic numerical analysis of the two-equation Reynolds-Averaged Navier-Stokes (RANS)
turbulence model to predict flow behaviour within a Ranque-Hilsch vortex tube (RHVT). Six geometric configurations,
defined by variation in inlet angle, are examined through three-dimensional computational fluid dynamics (CFD)
simulations. The investigation compared the performance of three widely adopted turbulence models: the standard k-ε, standard k-ω and SST k-ω models formulations. The simulations are considered to resolve the complex flow phenomena within the RHVT, characterised by strong swirling motion, compressibility effects, and intense turbulence that drive temperature separation. To enhance solution accuracy, particular emphasis is placed on mesh quality and near-wall resolutions with careful control of the dimensionless wall distance (y⁺). Model evaluation is carried out by comparing predicted temperature fields, outlet temperature at both cold and hot ends, and the overall flow structures. The results demonstrate that the standard k-ω model shows closure agreement with experimental data, which can be attributed to its improved treatment of the near-wall regions and its ability to capture the adverse pressure gradient more effectively. Overall, the findings underscore the importance of appropriate turbulence model selection in RHVT simulations and provide a useful basis for future numerical studies aimed at improving RHVT performance.