Statistically based approach to broadband liner design and assessment

摘要

A broadband liner design optimization includes utilizing in-duct attenuation predictions with a statistical fan source model to obtain optimum impedance spectra over a number of flow conditions for one or more liner locations in a bypass duct. The predicted optimum impedance information is then used with acoustic liner modeling tools to design liners having impedance spectra that most closely match the predicted optimum values. Design selection is based on an acceptance criterion that provides the ability to apply increasing weighting to specific frequencies and/or operating conditions. One or more broadband design approaches are utilized to produce a broadband liner that targets a full range of frequencies and operating conditions.

主权项

1. A method of designing an acoustic liner for aircraft, the method being implemented with a computer system comprising at least one computer processor, the method comprising:
obtaining geometric data corresponding to an aircraft structure that is to include an acoustic liner; determining a noise parameter to be evaluated; determining a desired outcome with respect to the noise parameter to be evaluated; determining a plurality of aircraft operating conditions, the plurality of aircraft operating conditions being evaluated simultaneously; providing a plurality of acoustic source pressure distributions for each aircraft operating condition to be evaluated, wherein the power and phase of each acoustic source pressure distribution is substantially random; utilizing acoustic prediction code that predicts at least one of acoustic propagation and acoustic radiation to provide a predicted parameter value corresponding to the noise parameter for a plurality of impedance inputs, wherein the impedance inputs comprise pairs of reactance and resistance values that are input into the code for each acoustic source pressure distribution; statistically combining the parameter values for each of the plurality of acoustic source pressure distribution to provide a combined parameter value for each pair of reactance and resistance inputs for each aircraft operating condition to be evaluated; utilizing predefined criteria relating to the noise parameter to be evaluated to identify a boundary comprising pairs of reactance and resistance values such that impedance values on a first side of the boundary comprise predicted optimum impedance values for each aircraft operating condition satisfy the predefined criteria and impedance values on the other side of the boundary do not satisfy the predefined criteria; selecting a plurality of predicted optimum impedance values corresponding to selected ones of the aircraft operating conditions; utilizing an impedance prediction code with the computer processor to design a liner, wherein the liner defines design impedance values corresponding to the selected predicted optimum impedance values; determining differences between the selected predicted optimum impedance values and the corresponding design impedance values; utilizing the differences to determine an optimum liner design that minimizes the effects of the differences according to a predefined criteria.