Tuned Generalised k-ω (GEKO) Turbulence Model Parameters for Predicting Transitional Flow Through Stenosis Geometries of Various Degrees

Stenosis geometries are constrictions of a biological tube that can be found in many forms in the human body. Capturing the flow field in such geometries is important. For this purpose, simulations were performed using the generalised k-ω (GEKO) turbulence model to study flow through stenosis geometries with throat constrictions of 75, 50 and 25% area reduction. Laminar flow conditions of Re = 2000 and 1000 were applied and the results were compared with experimental data. The effect of four GEKO parameters (CSEP, CNW, CJET and CMIX) on flow in the post-stenotic region was investigated by simulating a wide range of parameter values. Results showed that the CMIX parameter, combined with a modified GEKO blending function, had the greatest effect on axial velocity, velocity fluctuations and the location of the jet breakdown region. A CMIX value of 0.4 closely matched the experimental results for a 75% area reduction stenosis at Re=2000 and showed significant improvements over existing Reynolds-averaged Navier–Stokes models. The GEKO model was also able to closely match the axial velocity results predicted by previously published large-eddy simulation models under the same flow conditions. Furthermore, the GEKO model was applied to a realistic oral-to-tracheal airway model for a Reynolds number of 2000 and produced results consistent with the idealised stenotic tube.