  We propose an empirical extension of Yakhot's model of strong turbulence [V.
Yakhot, Phys. Rev. E 57(2) (1998)] that correctly describes the statistics of
longitudinal velocity increments not only in the inertial range but also for
larger scales up to the system length scale L. Two additional parameters are
introduced to the original equation for the probability density function of
velocity increments. These parameters can be motivated by physical arguments
and their values are fixed by large scale boundary conditions. The resultant
model ensures correct convergence of structure functions at the system length
scale, including vanishing slopes at L, and shows good agreement with
experimental data.
