A TIME-STEPPING METHOD FOR PREDICTING THE FLOW ABOUT POWERED LIFT VEHICLES AT HIGH ANGLES OF ATTACK

THE FLOW FIELD ABOUT POWERED LIFT VEHICLES CAN BECOME VERY COMPLEX DUE TO HIGH ANGLES OF ATTACK AND LIFTING JETS. IN ADDITION TO MODELING PROPULSION/AIRFRAME INTERACTIONS, THEREFORE, FLOW PREDICTION METHODS MUST TREAT THE PROBLEMS OF SEPARATION AND THE TRANSIENT EFFECTS OF PASSING VORTICAL STRUCTURES INTERACTING WITH THE AIRFRAME. ANALYTICAL METHODS, INC. (AMI) PROPOSES TO EXTEND ITS POWERED LIFT VERSION OF VSAERO BY INCORPORATING A TIME-STEPPING TECHNIQUE FOR TREATING SEPARATED FLOWS. THE BASIC VSAERO CODE HAS ALREADY BEEN SUCCESSFULLY APPLIED TO SEVERAL COMPLEX VSTOL CONFIGURATIONS; ROUTINESA PARABOLIZED NAVIER-STOKES (PNS) CODE IS BEING COUPLED WITH THE POWERED LIFT VERSION FOR BETTER TREATMENT OF ENTRAINMENT EFFECTS. THEPROPOSED EXTENSION WOULD INVOLVE THE INCLUSION OF ELLIPTIC TERMS IN THE PNS SEGMENT OF THE POWERED LIFT VERSION OF VSAERO NOT ONLY WIDEN THE SCOPE OF THE METHOD TO RELATED ASTOVL FLIGHT, BUT WOULD ALSO OFFER THE POTENTIAL TREATMENT OF TRANSIENT EFFECTS DURING TRANSITIONALFLIGHT. THE PROPOSED PHASE I EFFORT WOULD EXAMINE THE FEASIBILITY AND PRACTICALITY OF COUPLING THESE METHODS. A PHASE II EFFORT WOULD EXTEND AND REFINE THE TECHNIQUE WHERE NEEDED AND WOULD CONSOLIDATE THE METHOD INTO A PRACTICAL TOOL.