A spectral closure for inhomogeneous turbulence applied to the computation of an engine related flow

Abstract

The spectral model for inhomogeneous turbulence implemented in a finite element Reynolds Averaged Navier Stokes (RANS) solver is applied to the prediction of the intake stroke of a car engine in a simplified steady situation corresponding to the Belmabrouk experiment. In a valve jet region, the results of the spectral model are closer to the experimental data than those of classical models. An analysis of the spectra along mean streamlines suggests a possible explanation for this improvement: In a jet region, due to interaction between the small scales generated by the jet and the large scales present in the neighboring recirculation zones, the spectra are found to be in a nonequilibrium regime. Behind the valve, comparisons with experiment show that the spectral model leads to a better prediction of the integral length scale than the k-є model. In the impingement zone, although no experimental data were available, comparisons between the models suggest that the spectral model shares the limitations of the (k-є) model. Both models, relying on a scalar description of the turbulence, overpredict the turbulence intensity compared to a Reynolds stress closure. This motivates the effort to develop an extension of the spectral model in which a transport equation for each component of the spectral tensor is solved. .