Publications

Journal Articles

  1. Rachaprolu, J.S., and Greenwood, E., “Helicopter Noise Source Separation Using an Order Tracking Filter,” Journal of the American Helicopter Society, Vol. 69, No. 1, January 2024.
  2. Greenwood, E., Sim, B.W., and Boyd, Jr., D.D,  “Effects of Ambient Conditions on Helicopter Harmonic Noise Radiation: Theory and Experiment,” Journal of the American Helicopter Society, Vol. 69, No. 1, January 2024.
  3. Konzel, N.B., “Variability of Small Multirotor Aircraft Noise Measurements,” Noise Control Engineering Journal, Vol. 71, No. 6, November 2023.
  4. Coleman, D., Halder, A., Saemi, F., Runco, C., Denton, H., Lee, B., Subramanian, V., Greenwood, E., Lakshminaryan, V., and Benedict, M.,  “Development of ‘Aria,’ a Compact, Quiet Personal Electric Helicopter,” Journal of the American Helicopter Society, Vol. 68, No. 4, October 2023.
  5. Greenwood, E., Brentner, K.S., Rau, R.F., and Gan, Z.F.,  “Challenges and Opportunities for Low Noise Electric Aircraft,” International Journal of Aeroacoustics, June 2022.
  6. Stephenson, J.H., Watts, M.E., Greenwood, E., Pascioni, K.A., “Development and Validation of Generic Maneuvering Flight Noise Abatement Guidance for Helicopters,” Vol. 67, No. 1, January 2022, pp. 1-12.
  7. Greenwood, E. and Rau, R., “A Maneuvering Flight Noise Model for Helicopter Mission Planning,” Journal of the American Helicopter Society, Vol. 65, (2), April 2020, pp. 1–10.
  8. Greenwood, E., and Sim, B.W., “Effects of Crosswind Flight on Rotor Harmonic Noise Radiation,” Journal of Aircraft, Vol. 55, No. 5, September 2018, pp. 2137-2148.
  9. Greenwood, E., and Schmitz, F.H., “A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semiempirical Modeling,” Journal of the American Helicopter Society, Vol. 63, No. 3, July 2018, pp. 1-14.
  10. Greenwood, E., Schmitz, F.H., and Sickenberger, R.D., “A Semiempirical Noise Modeling Method for Helicopter Maneuvering Flight Operations,” Journal of the American Helicopter Society, Vol. 60, No. 2, April 2015, pp. 1-13.
  11. Stephenson, J.H., Tinney, C.E., Greenwood, E., Watts, M.E., “Time frequency analysis of sound from a maneuvering rotorcraft,” Journal of Sound and Vibration, Vol. 333, No. 21, October 2014, pp. 5324–5339.
  12. Greenwood, E., and Schmitz, F.H.  “Separation of Main and Tail Rotor Noise from Ground-Based Acoustic Measurements,”  Journal of Aircraft, Vol. 51, No. 2, March 2014, pp. 464-472.
  13. Greenwood, E., and Schmitz, F.H.  “Effects of Ambient Conditions on Helicopter Rotor Source Noise Modeling,” Journal of Aircraft, Vol. 51, No. 1, January 2014, pp. 90-103.

Conference Papers

  1. Weitsman, D., and Greenwood, E., “Passive Blade-Vortex Interaction Noise Reduction Using In-Blade Resonator Cavities,” presented at AIAA Scitech 2024, Orlando, FL, January 2024.
  2. Galles, M.B., Mark, D.M., Jones, M.G., and Greenwood, E., “Optimization of Variable Depth Acoustic Liners with Grazing Flow,” presented at AIAA Scitech 2024, Orlando, FL, January 2024.
  3. Yuan, K.J., Zachos, D.R., Langelaan, J.W., Greenwood, E., and Brentner, K.S., “Flight Path Planning for Minimization of Total Noise Exposure in Urban Air Mobility Operations,” presented at AIAA Scitech 2024, Orlando, FL, January 2024.
  4. Mcthane, E., Zahirudin, R.A.R., Hafner, A., Greenwood, E., and Palacios, J., “Effects of Varying Separation Distance on the Acoustics and Performance of Counter-Rotating Coaxial Rotors,” presented at the AIAA Aviation Forum 2023, San Diego, CA, June 2023.
  5. Rau, R.F., and Greenwood E., “A Parametric Investigation of Rotor-Rotor Interaction Noise Generation,” presented at the Vertical Flight Society 79th Annual Forum, West Palm Beach, FL, May 2023.
  6. Valente, V.T. , Greenwood, E., and Johnson, E.N., “An Experimental Investigation of eVTOL Flight State Variance on Noise,” presented at the Vertical Flight Society 79th Annual Forum, West Palm Beach, FL, May 2023.
  7. Botre, M., Wachspress, D., Greenwood, E., and Brentner, K.S., “Onboard Acoustic Prediction Method for VTOL Aircraft,” presented at the Vertical Flight Society 79th Annual Forum, West Palm Beach, FL, May 2023.
  8. Mukherjee, B., Jue, A., Theron, J.-P., Brentner, K.S., Greenwood, E., and Horn, J.F., “Investigation of Departure Transition Noise for Lift-Plus-Cruise eVTOL Aircraft,” presented at the Vertical Flight Society 79th Annual Forum, West Palm Beach, FL, May 2023.
  9. Zahirudin, R.A.R., Valente, V.T., Mcthane, E., Hafner, A., Birkbeck, Z., Yan, S., Greenwood, E., and Palacios, J., “The Effect of Phase Offset Angle for Coaxial Co-Rotating Rotors,” presented at the Vertical Flight Society 79th Annual Forum, West Palm Beach, FL, May 2023.
  10. Hur, K.W., Zachos, D.R., Brentner, K.S., and Greenwood, E., “Determining the Acoustic Far Field for Multirotor Aircraft,” presented at the Vertical Flight Society Autonomous VTOL Technical Meeting, Mesa, AZ, January 2023.
  11. Valente, V.T., Johnson, E.N., and Greenwood, E., “Implementation of a Phase Synchronization Algorithm for Mulirotor UAVs, ” IEEE/AIAA 41st Digital Avionics Systems Conference (DASC), Portsmouth, VA. September 2022.
  12. Rau, R.F., and Greenwood, E., “A Dynamic Wake Model for Multirotor Aircraft,” presented at the AIAA Aviation Forum 2022, Chicago, IL. June 2022.
  13. Gan, Z.F., Brentner, K.S., and Greenwood, E., “Time Variation of Helicopter Rotor Broadband Noise,” presented at 28th AIAA/CEAS Aeroacoustics Conference, Southampton, UK. June 2022.
  14. Greenwood, E., and Konzel, N.B.,  “Measurement and Characterization of Multirotor Unmanned Aerial System Noise,” presented at NOISE-CON 2022, Lexington, KY, June 2022.
  15. Konzel, N.B., and Greenwood, E., “Ground-Based Measurements of Small Multirotor Aircraft,” presented at the Vertical Flight Society 78th Annual Forum, Ft. Worth, TX. May 2022.
  16. Rachaprolu, J.S., and Greenwood, E., “Helicopter Noise Source Separation Using an Order Tracking Filter,” presented at the Vertical Flight Society 78th Annual Forum, Ft. Worth, TX. May 2022.*
  17. Mukherjee, B., Brentner, K.S., Greenwood, E., Theron, J.-P., and Horn, J.F., “An Investigation of Piloting and Flight Control Strategies on Generic eVTOL Noise,” presented at the Vertical Flight Society 78th Annual Forum, Ft. Worth, TX. May 2022.
  18. Zachos, D.R., Weist, L., Brentner, K.S., and Greenwood, E., “Variation in Helicopter Noise During Approach Maneuvers,” presented at the Vertical Flight Society 78th Annual Forum, Ft. Worth, TX. May 2022.
  19. Gan, Z.F., Mukherjee, B., Theron, J.-P., Botre, M., Brentner, K.S., Greenwood, E., and Horn, J.F., “A New Distributed Electric Propulsion Aircraft Simulation Tool for Coupled Flight Dynamics, Free Wake, and Acoustic Predictions,” presented at the Vertical Flight Society 77th Annual Forum, Virtual. May 2021.
  20. Coleman, D., Halder, A., Saemi, F., Runco, C., Denton, H., Lee, B., Subramanian, V., Greenwood, E., Lakshminaryan, V., and Benedict, M., “Development of ‘Aria’, a Compact, Ultra-Quiet Personal Electric Helicopter,” presented at the Vertical Flight Society 77th Annual Forum, Virtual. May 2021.*
  21. Zahirudin, R.A.R, Weitsman, D., Greenwood, E., Palacios, J., “The Development of a Coaxial Acoustics Test System for Rotor Noise,” presented at the Vertical Flight Society 77th Annual Forum, Virtual. May 2021.
  22. Gan, Z.F., Brentner, K.S., and Greenwood, E., “Time Variation of Rotor Broadband Noise,” presented at the 2021 Autonomous VTOL Technical Meeting and Electric VTOL Symposium, Virtual. January 2021.
  23. Weitsman, D., and Greenwood, E., “Parametric Study of eVTOL Rotor Acoustic Design Trades,” presented at AIAA Scitech 2021 Forum, Virtual. January 2021.
  24. Pascioni, K.A., Greenwood, E., Watts, M.E., Smith, C.D., Stephenson, J.H., “Medium-Sized Helicopter Noise Abatement Flight Test,” presented at the Vertical Flight Society 76th Annual Forum, Virginia Beach, VA. October 2020.
  25. Stephenson, J.H., Watts, M.E., Greenwood, E., Pascioni, K.A., “Development and Validation of Generic Maneuvering Flight Noise Abatement Guidance for Helicopters,” presented at the Vertical Flight Society 76th Annual Forum, Virginia Beach, VA. October 2020.*
  26. Trujillo, A.C., Greenwood, E., and Hill, D.R., “Helicopter Noise Footprint Depiction During Simulated Flight for Training,” in Advances in Human Aspects of Transportation. AHFE 2020. Advances in Intelligent Systems and Computing, Vol. 1212. July 2020.
  27. Greenwood, E., “Dynamic Replanning of Low Noise Rotorcraft Operations,” presented at the Vertical Flight Society 75th Annual Forum, Philadelphia, PA. May 2019.
  28. Christian, A., Caston, J., and Greenwood, E., “Regarding the Perceptual Significance and Characterization of Broadband Components of Helicopter Source Noise,” presented at the Vertical Flight Society 75th Annual Forum, Philadelphia, PA. May 2019.*
  29. Greenwood, E., “Estimating Helicopter Noise Abatement Information with Machine Learning,” presented at the American Helicopter Society 74th Annual Forum, Phoenix, AZ. May 2018.*
  30. Greenwood, E., “Real Time Helicopter Noise Modeling for Pilot Community Noise Awareness,” presented at NOISE-CON 2017, Grand Rapids, MI. June 2017.
  31. Greenwood, E., “Helicopter Flight Procedures for Community Noise Reduction,” presented at the American Helicopter Society 73rd Annual Forum, Fort Worth, TX. May 2017.
  32. Greenwood, E., Sim, B.W., and Boyd, D.D., “The Effects of Ambient Conditions on Helicopter Harmonic Noise Radiation: Theory and Experiment,” presented at the American Helicopter Society 72nd Annual Forum, West Palm Beach, FL. May 2016.*
  33. Watts, M.E., Greenwood, E., and Stephenson, J.H., “Measurement and Characterization of Helicopter Noise at Different Altitudes,” presented at the American Helicopter Society 72nd Annual Forum, West Palm Beach, FL. May 2016.
  34. Malpica, C., Greenwood, E., and Sim, B.W., “Parametric Investigation of the Effect of Hub Pitching Moment on Blade Vortex Interaction (BVI) Noise of an Isolated Rotor,” presented at the American Helicopter Society 72nd Annual Forum, West Palm Beach, FL. May 2016.
  35. Malpica, C., Greenwood, E., and Sim, B.W., “Helicopter Non-Unique Trim Strategies for Blade-Vortex Interaction (BVI) Noise Reduction,” presented at the American Helicopter Society Technical Meeting on Aeromechanics Design for Vertical Lift, San Francisco, CA. January 2016.
  36. Greenwood, E., Rau, R., May, B., and Hobbs, C., “A Maneuvering Flight Noise Model for Helicopter Mission Planning,” presented at the American Helicopter Society 71st Annual Forum, Virginia Beach, VA. May 2015.*
  37. Stephenson, J.H., and Greenwood, E., “Effects of Vehicle Weight and True Versus Indicated Airspeed on BVI Noise During Steady Descending Flight,” presented at the American Helicopter Society 71st Annual Forum, Virginia Beach, VA. May 2015.
  38. Greenwood, E., and Sim, B.W., “The Effects of Crosswind Flight on Rotor Harmonic Noise Radiation,” presented at the American Helicopter Society 69th Annual Forum, Phoenix, AZ. May 2013.
  39. Greenwood, E., Schmitz, F.H., and Sickenberger, R.D., “A Semi-Empirical Noise Modeling Method for Helicopter Maneuvering Flight Operations,” presented at the American Helicopter Society 68th Annual Forum, Fort Worth, TX. May 2012.*
  40. Watts, M.E., Snider, R., Greenwood, E., Baden, J., “Maneuver Acoustic Flight Test of the Bell 430 Helicopter,” presented at the American Helicopter Society 68th Annual Forum, Fort Worth, TX. May 2012.
  41. Greenwood, E., and Schmitz, F.H. “The Effects of Ambient Conditions on Helicopter Rotor Source Noise Modeling,” presented at the American Helicopter Society 67th Annual Forum, Virginia Beach, VA. May 2011.*
  42. Greenwood, E., and Schmitz, F.H., “A Parameter Identification Method for Helicopter Noise Source Identification and Physics-Based Semi-Empirical Modeling,” presented at the American Helicopter Society 66th Annual Forum, Phoenix, AZ. May 2010.
  43. Greenwood, E., and Schmitz, F.H., “Separation of Main and Tail Rotor Noise Sources from Ground-Based Acoustic Measurements Using Time-Domain De-Dopplerization,” presented at the 35th European Rotorcraft Forum, Hamburg, DE. September 2009.
  44. Greenwood, E., Schmitz, F.H., Gopalan, G., and Sim, B.W., “Helicopter External Noise Radiation in Turning Flight: Theory and Experiment,” presented at the American Helicopter Society 63rd Annual Forum, Virginia Beach, VA.  May 2007.*
  45. Schmitz, F.H., Greenwood, E., Sickenberger, R.D., Gopalan, G., and Sim, B.W., Conner, D.A., Moralez, E., and Decker, W.A., “Measurement and Characterization of Helicopter Noise in Steady-State and Maneuvering Flight,” presented at the American Helicopter Society 63rd Annual Forum, Virginia Beach, VA.  May 2007.

 *Selected as “Best Paper in Session”

 

Technical Reports

  1. Pascioni, K.A., Greenwood, E., Watts, M.E., Smith, C.D., Stephenson, J.H., “Medium-Sized Helicopter Noise Abatement Flight Test Data Report,” NASA TM-20210011459, NASA Langley Research Center, Hampton, VA. July 2021.
  2. Watts, M.E., Greenwood, E., Smith, C.D., and Stephenson, J.H., “Noise Abatement Flight Test Data Report,” NASA TM-2019-220264, NASA Langley Research Center, Hampton, VA. March 2019.
  3. Conner, D.A., Stephenson, J.H., Sim, B.W., Watts, M.E., Greenwood, E., and Smith, C.D., “Joint Eglin Acoustics Week 2013 Data Report,” NASA TM-2017-219681, NASA Langley Research Center, Hampton, VA. November 2017.
  4. Boyd, D.D., Greenwood, E., Watts, M.E., and Lopes, L.V., “Examination of a Rotorcraft Noise Prediction method and Comparison to Flight Test Data,” NASA TM-2017-219370, NASA Langley Research Center, Hampton, VA. January 2017.
  5. Watts, M.E., Greenwood, E., Sim, B.W., Stephenson, J.H., and Smith, C.D., “Helicopter Acoustic Flight Test with Altitude Variation and Maneuvers,” NASA TM-2016-219354, NASA Langley Research Center, Hampton, VA. December 2016.
  6. Watts, M.E., Greenwood, E., Smith, C.D., Snider, R., Conner, D.A., “Maneuver Acoustic Flight Test of the Bell 430 Helicopter Data Report,” NASA TM-2014-218266, NASA Langley Research Center, Hampton, VA. May 2014.

Thesis and Dissertation

  • Greenwood, E., Fundamental Rotorcraft Acoustic Modeling from Experiments (FRAME). Ph.D. Dissertation, Schmitz, F.H. and Hubbard, J.E. (Advisors). University of Maryland, 2011.
  • Greenwood, E., A Physics-Based Approach to Characterizing Helicopter External Noise Radiation from Ground-Based Noise Measurements. M.S. Thesis, Schmitz, F.H. (Advisor). University of Maryland, 2008.