Browsing by Author "de Souza, Francisco J."

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    Prediction of far-field noise from installed corrugated nozzles
    (AIAA, 2024-05-30) de Souza, Francisco J.; Lawrence, Jack; Cruz, Ricardo H.; Proenca, Anderson
    In this study, a reduced order model, devised by Lyu and Dowling, is used to predict the farfield installation noise of corrugated nozzles installed beneath a NACA aerofoil. A complementary investigation, detailed in another paper, reveals that employing square corrugations near the nozzle lip diminishes jet-surface interaction (JSI) noise compared to a round 40-mm diameter nozzle. This reduction is particularly notable for Strouhal numbers ranging from 0.3 to 0.9 and at high polar angles. The near-field pressure data, required for Lyu and Dowling’s model, is gathered using a circular array consisting of eight 1/8-inch microphones in the Doak Laboratory, at the University of Southampton, UK. Generally, the predictions align well with the experimental trends for Mach numbers ranging from 0.4 to 1 under static ambient flow conditions. Furthermore, it is observed that a minimum of four azimuthal modes must be available to accurately predict the noise generated by the corrugated nozzles. The effects of free-stream Mach number, particularly focusing on the predictive capacity of Lyu and Dowling’s model, are also investigated. Quantitative agreement at Strouhal numbers between 0.1 and 0.5 in evidenced.
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    Reduced-order model prediction of far-field mixing noise from internally-notched nozzles
    (AIAA, 2024-05-30) de Souza, Francisco J.; Lawrence, Jack; Proenca, Anderson
    This work presents a numerical investigation of the effect of internal notches on the reduction of jet mixing noise from round nozzles. The baseline jet is produced by the University of Southampton’s Doak Laboratory 40mm-diameter convergent, round nozzle. Numerical predictions of mixing noise for both round and internally-notched nozzles are conducted using a Generalized Acoustic Analogy that relies on Reynolds-Averaged Navier-Stokes (RANS) solutions of the nozzle flows, particularly the one proposed by Leib and Bridges. In this method, the RANS variables of interest, including mean axial velocity, Mach number, density, turbulence kinetic energy, and its dissipation rate, are interpolated onto a cylindrical structured grid suitable for aeroacoustic calculations. Subsequently, the respective Green’s function and a hybrid spectral-time source model are computed, and power spectral densities at various polar and azimuthal angles are predicted. Comparison between predictions and experiments demonstrates good qualitative agreement for both nozzles, although the inversion in trends at certain Strouhal numbers is not captured by the numerical model. Additionally, the significance of the numerical scheme’s order employed to solve the adjoint Green’s function is evaluated. To elucidate the noise reduction attributed to internal notches, distributions of turbulent kinetic energy are analyzed at different azimuthal cross-sections.