Aeroacoustic Study of a Strut Braced Ultra High Aspect Ratio Wing

To address the imperative of enhancing aerodynamic efficiency, reducing fuel consumption, and minimizing emissions in the next generation of air transportation, a substantial advancement in aircraft performance is essential. One of the configurations investigated for achieving these goals is the strut-braced Ultra-High Aspect Ratio Wing (UHARW). The addition of a bracing strut may have an aeroacoustic impact. In this paper, a noise assessment of the strut braced UHARW is performed. There are two types of sources in this configuration. The first is the dipole noise source due to the unsteady flow on the high-lift wing and in the wake of the bracing strut for example. The second is the trailing-edge noise of the main wing and the strut. To calculate the dipole noise sources, a Wall Modelled Large Eddy Simulation (WMLES) with a weakly compressible solver is employed to simulate the flow field around the basic elements of the high-lift wing. Subsequently, the time-varying pressure data on their surfaces serves as input for the Ffowcs Williams-Hawkings (FW-H) equation to calculate the far-field noise. These numerical methods are validated on the flow around a 30P30N three-element airfoil. The simulation results of the basic elements of the UHARW indicate that the joint of the strut and the wing increases the noise by approximately 3.5 dB over a wide frequency range locally. It is also shown that the noise of the existing flap side-edge is greater at frequencies between 300 and 1400 Hz. The noise of the full-span high-lift wing are estimated through the superposition of the noise generated by the individual basic elements in the time domain. The trailing edge noise of the main wing and strut is estimated using a semi-empirical method developed by Brooks, revealing that the noise spectrum of the strut contributes more at frequencies over 600 Hz, while that of the main wing contributes more at frequencies lower than 600 Hz. Based on a model of a realistic full-span UHARW wing, changes in the tone corrected Perceived Noise Level (PNLT) are estimated to quantity the potential impact on noise certification. The installation of the bracing strut results in an increase in the maximum PNLT of the wing source by approximately 0.76 PNLdB. This value does not consider the other airframe or engine noise sources on an aircraft.