Hybrid RANS-LES modelling of chevron nozzles with prediction of far field sound

Following on from Xia et al. (2009), hybrid large-eddy type simulations for chevron nozzle jet flows are performed at Mach 0.9 and Re = 1.03E6. Implicit or Numerical large- eddy simulation (ILES or NLES) is employed without any subgrid scale model. A RANS solution is patched into the near wall region. This makes the overall solution strategy hybrid RANS-LES. The disparate turbulence length scales, implied by these different modeling approaches, are matched using a Hamilton-Jacobi equation. Computations are contrasted for chevron penetrations of around 5 deg and 18 deg. The latter, with its more aggressive penetration is found easier to predict. Through the use of RANS simulations the state of the incoming boundary layer from the measurements is explored and the extent of any laminarization. A recently developed hybrid acoustic analogy model, Karabasov et al. (2010), informed with LES data is employed for far-field noise prediction. The acoustic source modeling is based on a mixture of RANS/LES techniques. For sound propagation a locally parallel mean flow model is used and the linearized Euler equation (LEE) is solved. The results are compared with the NASA SHJAR measurements and also with the predictions from a standard permeable-surface Ffowcs Williams-Hawkings (FWH) method based on the same LES data.