PREDICTION METHODS FOR POWERED-LIFT VEHICLE AERODYNAMICS

A NEW CAPABILITY FOR THE PREDICTION OF AERODYNAMIC CHARACTERISITIC OF POWERED-LIFT VEHICLES IS THE GOAL OF THISPROJECT. A PRESENTLY AVAILABLE AERODYNAMIC ANALYSIS COMPUTERCODE, VSAERO, IS APPLICABLE TO POWERED-LIFT AIRCRAFT CONFIGURATIONS. THE PROGRAM INCLUDES A METHOD WHICH CAN TREAT THE DIFFICULT GEOMETRIC SHAPES ASSOCIATED WITH SUCH CONFIGURATIONS AND HAS COUPLED ITERATIVE ROUTINES FOR VISCOUS/INVISCID EFFECTS AND FOR THE EFFECTS OF WAKE LOCATION. THE METHOD INCLUDES SIMPLE YET EFFECTIVE MODELING EXTENSIVE SEPARATION ZONES AND ALSO JETS USING FREE-VORTEX SHEETS TO ENCLOSE THE REGIONS OF DIFFERENT TOTAL PRESSURE. AT THIS TIME, HOWEVER, FREE-VORTEX SHEET TRAJECTORIES THAT DEVIATE FROM THE ONSET FLOW DIRECTION BY A LARGE AMOUNT CANNOT BE RELIABLY TREATED BY THE INSTALLED ROUTINES.THUS, THE TREATMENT OF LARGE JET DEFLECTION ANGLES IS EXCLUDED. THE OBJECTIVE OF THE PRESENT STUDY IS TO REMOVE THIS RESTRICTION. THIS AIM IS ACHIEVED BY DEVELOPING AN ALTERNATIVE TREATMENT OF THE FREE-VORTEX SHEETS IN THE CODE ALLOWING THEM TO MOVE ANYWHERE IN THE FLOW FIELD, INCLUDING "UPSTREAM". THE APPLICATION RANGE OF THE PROGRAM WOULD THEN BE EXTENDED TO INCLUDE V/STOL AIRCRAFT AT LOW TRANSITION SPEEDS AND IN HOVER WITH OR WITHOUT GROUND EFFECT.