FLUCTUATING INFLOW CONDITIONS FOR TIME-DOMAIN BOUNDARY ELEMENT METHOD FOR AIRFOIL-TURBULENCE INTERACTION NOISE

ABSTRACTAcoustic radiation from an airfoil subjected to a real flow isone such effect induced by turbulence and demands highperformancecomputing for its prediction numerically. Themethods which are available now range back fromanalytical ones, which are fast but not precise enough tocapture nonlinear effects, to the numerical one, whichheavily depends on the computing resources. This studyfocuses on the development, validation, and demonstrationof a transient, two-dimensional stochastic method for theprediction of leading edge noise. A new approach to modelthe noise from turbulent flows is presented to bridge the lowfidelity and high-fidelity methods. The method relies on theclassical view of turbulence as a superposition of randomvortices convected with the mean flow. The fluctuatingvelocity is formulated using the scalar potential given by aconvolution product which furnishes a solenoidal velocityfield. The system is then optimised stochastically to createa realistic turbulence field based on a target energy spectrausing an evolutionary optimisation algorithm. The pressuresignals are then used to calculate the sound radiation usingFfowcs-Williams and Hawkings analogy. The approach hasbeen validated against analytical solutions of the linearizedwave equations and experimental data available.