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    Prediction methods for helicopter rotor blade noise and flow-sound interactions in nozzle flow
    (Institute of Science And Technology, 2011-11-18) Zafer, Baha ; Delale, Can Fuat ; 521052101 ; Advanced Technologies ; İleri Teknolojiler
    There are two part in this study, one is related with asymptotic approach to helicopter rotor blade noise and second part is computational aeroacoustics which is used in order to solve the interaction between flow and sound in the transonic nozzle.In the first of study that provides asymptotic formulas for the far field of the mth harmonic components of the acoustic radiation from a B-bladed subsonic single rotational propeller, in the asymptotic limit as mB??. Asymptotic expressions of subsonic propeller noise of Parry and Crighton accounting for contributions from airfoil thickness and loading are refined. These expressions are found by the application of Laplace?s method to the integrals of steady loading and of blade thickness distributions over the surface of the blade using the Debye approximation. In particular, second order correction to single rotational propeller noise expression of Parry and Crighton is obtained for the harmonic components Pm of the subsonic propeller noise. In the second part of this study, an acoustic wave is introduced at the nozzle exit and the sound wave that travels upstream through the transonic nozzle is to be calculated using high order computational aeroacoustics schemes. In this study, there are two different nonreflecting boundary conditions are used for the inflow and outflow boundary conditions. In the case of standard nonreflecting boundary condition of Thomson and alternative nonreflecting boundary conditions is used in the present work. Time integration is computed by using fourth order Runge ? Kutta time marching scheme for the nonuniform grid. The well agreement is obtained between exact solution and computed results.