Advanced turbulence and transition models have been implemented into NASA Glenn Research Center’s TURBO code (Reynolds-Averaged Navier-Stokes solver) to improve and extend its capability of modeling turbomachinery flows. This will enable better prediction of steady and unsteady loads on fan and compressor blades at on-design and off-design operating conditions. As a result, aeroelastic vibrations and high-cycle fatigue failures in gas turbine engine blades will be better predicted and avoided over a wider range of operating conditions. Avoidance of aeroelastic blade vibrations and fatigue failures will improve the safety and reliability of aircraft propulsion systems.
As the flow goes over blade surfaces, boundary layers are formed that may be laminar, transitional, or turbulent. The accurate modeling of these flow regimes is necessary for an accurate prediction of steady and unsteady loads on the blade. When a turbomachinery blade row operates at off-design conditions, the angle of incidence of the flow can be quite large, resulting in separation of the flow away from the surface over a portion of the blade. Numerical modeling of separated flows is very challenging and requires accurate modeling of transition and turbulence. Prior to the current work, the TURBO code required the user to prescribe a transition location on the blade surface at which the flow model was abruptly changed from laminar to turbulent. In reality, the flow goes through a transition region in which the flow is neither laminar nor fully turbulent. As a result of the current work, the TURBO code now includes the capability to calculate a transition onset location and to calculate a modified turbulent viscosity based on a transition model. The transition model now implemented into the TURBO code is the Solomon-Walker-Gostelow model, and the turbulent eddy viscosity is now modeled using the Spalart-Allmaras turbulence model.
The TURBO code with the improved modeling capability described here was used to model flow through Glenn’s Transonic Flutter Cascade (ref. 1). Calculations were carried out at low and high flow incidence angles at which experimental data were previously acquired by Glenn researchers. For the high-incidence condition, the new turbulence and transition modeling capability clearly showed an improved flowfield prediction. In particular, the pressure plateau noted in the experimental data, and not correctly modeled with the assumption of fully turbulent flow, was captured well with the new modeling capability.
The research work described here was performed under a grant to Dr. Vincent R. Capece (University of Kentucky, Paducah, KY) and Dr. Max F. Platzer (Naval Postgraduate School, Monterey, CA). This work was supported by the Ultra-Efficient Engine Technology Project, Dr. Robert J. Shaw, manager.
Last updated: November 14, 2007
Responsible NASA Official:
Gynelle.C.Steele@nasa.gov
216-433-8258
Point of contact for NASA Glenn's Research & Technology reports:
Cynthia.L.Dreibelbis@nasa.gov
216-433-2912
SGT, Inc.
Web page curator:
Nancy.L.Obryan@nasa.gov
216-433-5793
Wyle Information Systems, LLC
