TURBULENT ROTATING FLOW CALCULATIONS - AN ASSESSMENT OF 2-EQUATION ANISOTROPIC AND REYNOLDS STRESS MODELS

The stress field in a rotating turbulent internal flow is highly aniso tropic. This is true irrespective of whether the axis of rotation is a ligned with or normal to the mean flow plane. Consequently, turbulent rotating flow is very difficult to model. This paper attempts to asses s the relative merits of three different ways to account for stress an isotropies in a rotating flow. One is to assume an anisotropic stress tensor, another is to model the anisotropy of the dissipation rate ten sor, while a third is to solve the stress transport equations directly . Two different near-wall two-equation models and one Reynolds stress closure are considered. All the models tested are asymptotically consi stent near the wall. The predictions are compared with measurements an d direct numerical simulation data. Calculations of turbulent flows wi th inlet swirl numbers up to 1.3, with and without a central recircula tion, reveal that none of the anisotropic two-equation models tested i s capable of replicating the mean velocity field at these swirl number s. This investigation, therefore, indicates that neither the assumptio n of anisotropic stress tensor nor that of an anisotropic dissipation rate tensor is sufficient to model flows with medium to high rotation correctly. It is further found that, at very high rotation rates, even the Reynolds stress closure fails to predict accurately the extent of the central recirculation zone.