Characteristics of Turbulence in a Turbofan Stage

Two-equation turbulence models are commonly used in the simulation of turbomachinery flow fields, but there are limited experimental data available to validate the resulting turbulence quantities. Experimental measurements are available from NASA’s Source Diagnostic Test (SDT), a 1/5th scale model representation of the bypass stage of a turbofan engine. Detailed unsteady hot-wire anemometer data were taken at two axial locations between the rotor and fan exit guide vanes (FEGVs). Here, an accurate and consistent procedure is used to obtain the turbulent kinetic energy, dissipation rate, and integral length scale from structure functions calculated using the SDT data. These results are compared to the solutions provided by four proprietary CFD codes that employ two-equation turbulence models. The simulations are shown to predict the turbulent kinetic energy and length scale reasonably well as well as the trend in mean dissipation. The actual mean dissipation rates differ by nearly two orders of magnitude due to a difference in interpretation between the classical definition and what is used in CFD.