Aerodynamic noise from long circular and non-circular cylinders using large eddy simulations

Flow-induced aerodynamic noise from four cylindrical shapes of infinite length at a low subcritical flow regime is studied using Large Eddy Simulation (LES) and acoustic analogy. Numerical simulations are performed for short-span (length to diameter ratio of 3) cylinders, and a sound correction method based on equivalent/spatial coherence length has been applied to estimate noise from long-span cylinders. An attempt is made to compare spatial coherence lengths of four cross-sections at the same Reynolds number (Re). The sound correction method that is well established for circular cylinders proved effective for non-circular cross-sections also. Owing to the limitation in computational capacity, a well-resolved LES is still unachievable for higher Re flows and long-span cylinders without adopting a sound correction methodology. A grid resolution based on the characteristic length and velocity scale was adopted in simulation and proved effective for computing aerodynamic and aeroacoustic characteristics. An ‘effective frequency band’ of sound pressure level-frequency curve is proposed that predicts over 99.5% of the overall sound pressure level, and features of this band for four cross-sections are presented.