TRANSITION TO TURBULENCE IN COMPLEX AERODYNAMIC FLOWS

WE PROPOSE TO DEVELOP A USER-FRIENDLY CFD TOOL BASED ON THE SPECTRAL-ELEMENT, GENERAL GEOMETRY COMPUTER CODE NEKTON TO COMPUTE THE TRANSITION TO TURBULENCE IN COMPLEX GEOMETRY FLOWS OF INTEREST TO NASA. THE SPECTRAL ELEMENT FLOW SOLVERS IN NEKTON OFFER THE ADVANTAGE OF ACCURACY, EFFICIENCY, AND ROBUSTNESS IN COMPARISON WITH OTHER NUMERICAL METHODS. THE SPECTRAL ELEMENT NEKTON CODE WILL BE ENHANCED THROUGH THE INTRODUCTION OF A RENORMALIZATION-GROUP-BASED SUBGRID MODEL TO ALLOW THE CODE TO CALCULATE ALL THE WAY FROM THE LAMINAR FLOW STATE THROUGH TO DEVELOPED TURBULENCE. IN PHASE I, PROTOYPICAL COMPLEX GEOMETRY FLOWS WILL BE STUDIED, THE SUPERCIRITCAL VERSUS SUBCRITICAL CHARACTER OF SHEAR FLOW TRANSITION IN COMPLEX GEOMETRY WILL BE EXPLORED, AND THE RNG SUB-GRID MODEL WILL BE TESTED. IN PHASE II, NEKTON WILL BE EXTENDED INTO A GENERAL PURPOSE TRANSITION SIMULATION TOOL FOR ENGINEERING THROUGH IMPROVED MESHING SCHEMES, IMPROVED SUBGRID MODELS AND GENERAL PURPOSE INTERFACES TO WORKSTATION-BASED USERS.