Subgrid-scale contributions to Lagrangian time correlations in isotropic turbulence

The application of large-eddy simulation(LES)to particle-laden turbulence raises such a fundamental ques-tion as whether the LES with a subgrid scale(SGS)model cancorrectly predict Lagrangian time correlations(LTCs).Mostof the currently existing SGS models are constructed basedon the energy budget equations.Therefore,they are able tocorrectly predict energy spectra,but they may not ensure thecorrect prediction on the LTCs.Previous researches investi-gated the effect of the SGS modeling on the Eulerian timecorrelations.This paper is devoted to study the LTCs in LES.A direct numerical simulation(DNS)and the LES with aspectral eddy viscosity model are performed for isotropicturbulence and the LTCs are calculated using the passivevector method.Both a priori and a posteriori tests are car-ried out.It is observed that the subgrid-scale contributions tothe LTCs cannot be simply ignored and the LES overpredictsthe LTCs than the DNS.It is concluded from the straininghypothesis that an accurate prediction of enstrophy spectrais most critical to the prediction of the LTCs.