• Dr. Dennis McLaughlin
  • The Pennsylvania State University
  • 108 Surge Building
  • 4:00 p.m.
  • Faculty Host: Dr. K. Todd Lowe

Penn State research addresses the need for jet noise reduction for modern military aircraft. The noise induced hearing loss suffered by Navy personnel working in close proximity to tactical aircraft, particularly for carrier-based operations, is of increasing concern to the US Navy. However, acoustic measurements for such exhaust jets are scarce, due to the cost involved in making full scale measurements and the lack of details about the exact geometry of the nozzles.  Past efforts at Penn State University, in partnership with the NASA Glenn Research Center and GE Aviation, was focused on developing methodology for using data obtained from small and moderate scale experiments to reliably predict the most important components of full scale engine noise.  The experimental results demonstrated good agreement between small scale and moderate scale jet acoustic data, as well as between heated jets and heat-simulated ones.

Our most recent efforts have developed a methodology and device for the reduction of supersonic jet noise.  The goal is to develop a practical active noise reduction technique for low bypass ratio turbofan engines.  The method involves precise blowing into the divergent section of the engine exhaust nozzle to produce fluidic inserts that mimic “hard walled” corrugated inserts.  By altering the configuration and operating conditions of the fluidic inserts, active noise reduction for both mixing and shock noise has been obtained.  Substantial noise reductions have been achieved for mixing noise in the maximum noise emission direction and in the forward arc for broadband shock-associated noise.  To achieve these reductions (on the order of 5 and 2 dB for the two main components respectively) practically achievable levels of injection mass flow rates have been used.  The total injected mass flow rates were less than 4 % of the core mass flow rate and the effective operating injection pressure ratio was maintained at or below the same level as the nozzle pressure ratio of the core flow.  Refinement and optimization of this technique is being pursued at Penn State University.