A RANS-based prediction method for the airfoil broadband trailing edge noise

A RANS (Reynolds averaged Navier-Stokes)-based prediction method for the airfoil turbulent boundary layer trailing edge noise was developed. The Navier-Stokes equations were firstly reformulated to the form that the left hand side was a linear wave propagation operator and the right hand side was the source term that consists of Reynolds stresses. To reduce the computation time and avoid the spatial singularity of the Green function, the adjoint Green functions method was employed to compute the exact or 'tailored' Green functions; moreover, the source term was generated by the RANS-based modeling method. Application of the present method on the broadband trailing edge noise of NACA0012 airfoil was made to validate the present method. The OpenFOAM solver was applied into the mean flow computation of NACA0012 airfoil and the Green function for semi-infinite flat plate under uniform mean flow was used to approximate that of thin airfoil. The predicted spectrum of the broadband trailing edge noise indicates that: for various incoming flow velocity and angle of attack, the current method can not only predict the amplitude and the peak frequency accurately, but also the whole spectra is in good agreement with the current available experiment data (±3 dB), which demonstrates the accuracy and applicability of the method.