The Research And Application Of The Nonlinear Turbulent Model Based On The Rotating Field

The rotating turbulent flow is one of the most complex in the engineering, which is widely used in the fluid machinery such as pump, fan, compressor and hydro-turbine. Because of the effects of rotating, the structure of the flow field has been changed. In the early, experiment method is commonly used to research the rotating turbulent flow, the numerical simulation is widely used with the development of computational fluid mechanics(CFD). Among common RANS method, two-equation turbulent models based on the Boussinesq’s hypothesis of linear eddy viscosity are widely used in the engineering, however, when used to simulate rotating turbulent flow there is two demands, that is the hypothesis of isotropy and coordinate indifference, the former is the result of Boussinesq’s hypothesis while the latter is the result of the strain rate tensor unique dependence, they causes some negative consequences, such as can’t accurately predict the second flow and represent the rotary effect in the non-inertial system.Based on the three-dimensional RANS and explicit algebraic stress models (EASM), a new method, which the extended intrinsic mean spin tensor is instead of the intrinsic mean spin tensor, is developed to simulate the turbulent flow in the span-wise rotating duct. The comparison of the simulating results with the experiment shows that the method is more suitable to solve the anisotropy flow, then the influence of rotation on mean flow and turbulent structures are analyzed.The method is also applied to simulate the internal flow of multi-blade centrifugal fan. The predicting aerodynamic performance is well accord with the experiment, it shows again that the computational model and method is reliable. The analysis of the velocity and pressure distribution in different working condition shows that the lower energy fluid is accumulated in the front plane and some second vortex appears in the impeller passage under the action of the adverse pressure gradient and the fluid turning from the axial direction to the radial direction. There is separated flow in the suction side near the leading edge of impeller, and the flow attaches near the trailing edge of impeller, which forms the closed separated flow. The phenomenon of the separated flow in the shroud is more severe than the middle plane and the hub. It is easier to generate separated flow in the impeller passage at lower flow rate. Besides. the streamline in the impeller passage is also analyzed and some flow mechanism of the separated flow in the passage is revealed.