TRASONIC WALL INTERFERENCE ASSESMENT AND CORRECTION

IN ORDER TO ESTIMATE THE PERFORMANCE OF MODELS TESTED IN TRASONIC WIND TUNNELS, AND TO ACHIEVE MAXIUM BENEFIT FROM SUCH TEST, IT IS NECESSARY TO MAKE ACCURATE CORRECTIONS FOR EFFECTS OF WALL INTERFERENCE. AND IMPROVED CONCEPT FOR THE ASSESMENT AND CORRECTION OF WALL INTERFERENCE IN TRASONIC TUNNELS IS THE FOCUS OF THIS PROJECT. UNTIL RECENTLY, THE ONLY AVAILABLE ANALYSIS OF INTERFERENCE WAS A CLASSICAL LINEAR THEORY WHICH DOES NOT PRODUCE SUFFICIENTLY ACCURATE FORMULAE FOR PRACTICAL USE IN THE TRASONIC REGIME. WORK ON WALL INTERFERENCE CORRECTION PROCEDURES FOR TRASONIC TESTS IS IN THE RESEARCH STAGE: A RECENTLY COMPLETED TRASONIC, THREE-DIMENSIONAL PROCEDURE INVOLVES SMALL DISTURBANCE APPROXIMATIONS AND IRROTATIONAL FLOW ASSUMPTIONS THAT MAKE THIS METHOD GENERALLY INADEQUATE FOR PREDICTING WALL INTERFERENCE EFFECTS FOR REAL TEST MODELS. IT IS, THEREFORE, THE OBJECTIVE OF THIS WORK TO DEVELOP AN ACCURATE CORRECTION WHICH DOES NOT NEGLECT ROTATIONAL EFFECTS AND MAKES NO SMALL DISTURBANCE ASSUMPTIONS. IN PHASE I, A PROCEDURE APPLICABLE TO THREE- DIMENSIONAL CONFIGURATIONS IS DEVELOPED. THE PROCEDURE IS TESTED USING A COMPUTER CODE DEVELOPED IN PILOT FORM AND IS LIMITED TO TWO-DIMENSIONAL CONFIGURATIONS. THE IDEAS FORMULATED AND TESTED IN PHASE I ARE THE BASIS FOR A PHASE II EFFORT FOR DEVELOPING A USER-ORIENTED COMPUTER CODE TO CALCULATE WALL INTERFERENCE CORRECTIONS FOR AIRCRAFT CONFIGURATIONS.