Measurements and wall Modeled LES Simulation of Trailing Edge Noise Caused by a Turbulent Boundary Layer

A successful comparison between CFD-CAA and measurements of trailing edge noise is shown for a highly loaded and cambered NACA 5510 airfoil at a chord based Reynolds number of aprox. 1 million placed in a quiet low Mach number flow. The simulation is based on a new variant of the DES - the Improved Delayed Detached Eddy Simulation (IDDES).

The flow is fully attached to the airfoil and therefore only the small turbulent boundary structures that interact with the trailing edge generate significant broadband noise in the far field. The IDDES approach is designed to extend the LES region of the original DES approach (hybrid RANS/LES) from Spalart et. al. (1997) to the turbulent boundary layer, as proposed first by Travin et. al. in 2006. The non-zonal blending occures therefore inside the boundary layer - the RANS model acts as a wall model for the LES. The actual work shows the capabilities of this novel approach for the simulation of broadband noise for attached flows. The simulation is compared to measurements from the EC Lyon including PIV and LDA data around the airfoil and unsteady on-wall pressure measurements near the trailing edge. Far field computations are carried out by applying the Ffowcs–Williams and Hawkings analogy to the unsteady wall pressure field and compared to acoustic measurements as well as to a far field prediction based on a trailing edge noise model that is applied to the experimental aerodynamic pressure field.