Based on ideas of Prandtl, Hinze proposed to describe turbulence prope
rties - e.g. the Reynold's shear stress - as those of a visco-elastic
fluid, including a description of memory behaviour. For the time-avera
ged quantities of a quasi-stationary flow an analogous non-local appro
ach can be formulated. From this, by assuming a perfect coherence over
a well defined distance, the difference-quotient turbulence model has
been obtained.