Description: Research in Flight and Auburn University are proposing to develop a robust tool and methodology to allow the simulation and modeling of acoustic signatures for Distributed Electric Propulsion (DEP) air vehicle concepts in the conceptual design phase. These new tools will enable the study of aeroacoustics in much greater detail and with greater fidelity than heretofore deemed practical in the early phases of design. Early aeroacoustic prediction capability will expose potentially problematic acoustic signatures so that configuration changes, and both active and passive noise control technologies can be introduced during conceptual design, thus resulting in significant cost and schedule efficiencies. In this proposed activity, a simplified acoustic formulation based on the Farassat 1A solution of the Ffowcs Williams-Hawkings (FW-H) Equation will be used. This 1A formulation is a solution of the FW-H equation for thickness and loading noise by integration over the body surface flow, computed by the vorticity-flow solver. It has been shown with Vortex Lattice flow solvers that the above acoustic formulations can lead to substantial savings in complexity and solution times while maintaining a reasonable level of accuracy for early design stages, especially for rotor noise problems. This activity will extend these findings and couple a simple, easy-to-use, lower-order acoustics tool to a higher-order panel solver such as FlightStream®, which is already in use by NASA for DEP aero-propulsion analysis FlightStream® has been developed by Research in Flight as a fast, accurate, flow solver using surface-vorticity on the outer mold line of an aircraft. FlightStream® is strikes the proper balance between modeling fidelity and computational tractability. The FlightStream® unsteady solver will be used to solve for the unsteady aero-propulsive loads on the DEP vehicle. This activity will result in the creation of a conceptual-phase Aeroacoustics Toolbox in FlightStream®.

Benefits: The FlightStream® Aeroacoustics Toolbox developed during this effort can be used by NASA to generate a Modeling & Simulation (M&S) workbench to test upcoming noise control technologies under development at NASA and its partner organizations. Support NASA Aeronautics Research Mission Directorate (ARMD) strategic thrusts for the Advanced Air Vehicles Program (AAVP). The Aeroacoustics Toolbox in FlightStream® will be made available to NASA users to evaluate acoustic signatures of the next generation of DEP aircraft concepts.

Support educational applications. In a classroom, this tool enables students to test effects of aero-propulsive concepts on acoustic signatures. This toolbox provides effective support for acoustics-related certification process. It offers an analytical basis for flight testing. This toolbox also enables aircraft manufacturers to shorten design cycles, because of its integrated design environment.