Welcome to CRAFT-Tech

Jet Noise Simulations: While significant advances have been made in our ability to analyze unit problems associated with aircraft exhaust flowfields, the analysis of realistic problems accounting for actual propulsive flowpaths and jet aerodynamic interactions, are at a rudimentary level. Geometric complexities associated with resolving details of the propulsive flowpath (from core/fan turbine exit section through ejector to nozzle exit plane) have precluded the performance of complete simulations. At present, simplified problems can be analyzed (e.g. several lobed sections) at a unit problem level. Aerodynamic interactions of the jet and aircraft wake have generally been neglected by the aeroacoustics community despite noted distortions attributable to such effects which can have a significant influence on noise emission. Noise prediction methods using data from advanced unsteady (LES) simulations have not dealt with geometric complexities and nonlinear issues. A multi-faceted program of work is outlined which takes cognizance of present limitations in analyzing real problems and formu-lates a building-block approach for development and assessment of advanced methodology starting from operational computer codes which have already analyzed the varied unit problems associated with aircraft exhaust flowfields.

Jet Noise Control: Laboratory experiments being performed by Dr. John M. Seiner at the National Center for Physical Acoustics (NCPA) U.Miss and others are investigating a variety of passive (non-pulsatile) jet noise reduction concepts that include use of chevrons, micro-jets and hybrid concepts. CRAFT Tech has been using RANS CFD methodology to evaluate and refine these varied concepts. Studying noise reduction concepts by RANS can reveal the change these concepts are producing to the flow and turbulence structure and thus how effective they are in reducing noise on a relative basis. Relating these changes towards their qualitative effect on noise suppression is still an active area of research. Work now in progress includes the use of new hybrid concepts and appears quite promising.