Unsteady CFD for Flow Noise Modeling
Bryan, B. Skyler (NSWC Carderock)
Electromagnetic and Acoustics Applications
Space-time-resolved computational fluid dynamic simulations, using the large eddy simulation approach, are exercised to improve understanding of the underlying physics and to improve the fidelity of predictions of sound generated by the interaction of low Mach number turbulent flows with ship components. These simulations serve as virtual experiments that can provide vastly more detail of the flow physics relative to physical testing. This presentation discusses implementation and results of several large eddy simulations of free turbulent and turbulent boundary layer flows interacting with canonical surface shapes. Specifically, simulations have been executed on the DoD HPC, requiring parallel execution over thousands of processors, for turbulent boundary layer flows over a flat plate, a plate with an array of cube-shaped protrusions, and a NACA 0012 airfoil. Near-wall, turbulent flows were resolved to within 1 viscous length from the flow surface to relate the turbulent flow mechanisms with the surface unsteady stresses, pressure and shear components, which are the primary sound sources for low Mach number flows. The coupling of structural acoustic transfer functions and TBL information are ultimately used to predict sound. The implications of these results for future simulation strategies and flow noise modelling are also discussed.