2.4.1 Distributed Exhaust Nozzles

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2.4.1 Distributed Exhaust Nozzles
2.4 High Performance Components
K. K. Ahuja (Georgia Tech)

• Science Technology Objective(s)
• Objective 1 - Model and Facilities Development
• Objective 2 - Testing and Data Acquisition
• Objective 3 - Model Validation and Noise
  Prediction

• Collaborations
• Government and Industry - To compare notes with
  Northrop Grummans and NASA Langleys in-house
  programs
• Synergism with existing programs - Completed a
  one-year study recently for Glenn (NAG3-6221)on
  the feasibility of distributed exhaust nozzle for
  noise reduction. This study will build upon that
  foundation

• Milestones/Accomplishments

• Proposed Approach
• Step 1 Modify current design to understand
  trailing-edge geometry effects and role of fluid
  shielding
• Step 2 Establish acoustic performance under
  Flight Simulation
• Step 3 Validate theoretical models and develop
  prediction schemes

• NASA Relevance/Impact
• Relevance/impact 1 Helps Reduce Noise

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2.4.1 Proposed Approach

• The basis of this approach is that large number
  of small jets, characteristic of a distributed
  exhaust produce noise at frequencies outside the
  human hearing range. Also, if spaced suitably,
  the jets coalesce at smaller velocities, thus
  producing low-amplitude noise at low frequencies.
• Design and fabricate a distributed nozzle with
  different wedge geometries to understand the role
  of the trailing edge of the nozzle.
• Mount the nozzle in an anechoic flight
  simulation facility and test its effectiveness
  in reducing noise as a function of jet exit
  velocity and flight speed.
• Measure the effect of flight on the fluid
  shielding of noise provided by individual slot
  jets.
• Measurements to include farfield acoustic
  signatures, flow visualization, and PIV data.
• Correlate the data where possible with
  theoretical models and develop a noise prediction
  scheme