K\'arm\'an--Howarth Theorem for the Lagrangian averaged Navier-Stokes alpha model

Abstract

The K\'arm\'an--Howarth theorem is derived for the Lagrangian averaged Navier-Stokes alpha (LANS$-\alpha$) model of turbulence. Thus, the LANS$-\alpha$ model's preservation of the fundamental transport structure of the Navier-Stokes equations also includes preservation of the transport relations for the velocity autocorrelation functions. This result implies that the alpha-filtering in the LANS$-\alpha$ model of turbulence does not suppress the intermittency of its solutions at separation distances large compared to alpha.