Affordable detached eddy simulations of dual-stream jet structures related to shock cell noise

Pursuing the sustainable aviation targets of the Advisory Council for Aviation Research and Innovation in Europe (ACARE) in Flightpath 2050 and, equivalently, the N+2 and N+3 goals by NASA, aircraft engine manufacturers are developing Ultra High Bypass Ratio (UHBR) turbofans, such as the PW1500G and the UltraFan, using technology demonstrators like in the Clean Sky 2 Joint Undertaking OU). By increasing the bypass ratio, a greater portion of the engine thrust and of its associated jet noise comes from the bypass stream which, with a fan operated near its design pressure ratio of 1.4 (reduced from 1.6 of earlier engines), still generates a cold under-expanded jet and unwanted shock-cell noise at cruise. Modern mission-optimized engines require affordable numerical methods able to capture the essential flow physics for performing multi-point optimizations of the propulsion system, including predictions of thrust and jet noise. In this work, the authors apply Detached Eddy Simulations to a dual-stream nozzle representative of a UHBR configuration. The large-scales, whilst coarse-grained compared to LES, are shown by acoustic analogy be sufficient for providing physically sound broadband shock cell noise spectra.