Large eddy simulation for jet noise: the importance of getting the boundary layer right

Abstract

Large eddy simulations of an isothermal Mach 0.9 jet issued from a convergent-straight nozzle are performed at Reynolds number 1 × 10 6 .The flow configuration and operating conditions match the companion experiment conducted at the PPRIME Institute, Poitiers.To replicate the effects of the boundary layer trip present in the experiment and to ensure a turbulent jet, localized adaptive mesh refinement, synthetic turbulence, and wall modeling are used inside the nozzle.This leads to fully turbulent nozzle-exit boundary layers and results in significant improvements for the flow field and sound predictions, compared to those obtained from the typical approach based on laminar flow assumption in the nozzle.The far-field noise spectra now match the experimental measurements to within 0.5 dB for relevant angles and frequencies.As a next step toward better understanding of turbulent jet noise, the large database collected during the simulation is currently being used for reduced order modeling and wavepacket analysis.