A MODEL OF A HOMOGENEOUS ISOTROPIC TURBULENT-FLOW AND ITS APPLICATIONFOR THE SIMULATION OF CLOUD DROP TRACKS

A model of a homogeneous isotropic turbulent Bow is presented. The mod el provides different realizations of the random velocity field compon ent with given correlation latitudinal and lateral functions and a spa tial structure which obeys the Kolmogorov theory of homogeneous and is otropic turbulence. For the generation of the turbulent flow the struc tural function of the flow in the form suggested by Batchelor (Monin a nd Yaglom, 1975) was used. This function describes the spectrum of tur bulence both in the viscous and inertial ranges. The isotropy and homo geneity of the velocity field of the model are demonstrated. The model is aimed at simulating the ''fine'' features of drop's (aerosol parti cles') motion, such as the deviations of drops' velocity from the velo city of the flow, detailed structures of drops' tracks, related to dro ps' (particles') inertia. The model is intended also For the purpose o f studying cloud drops' and aerosol particles' motion and their diffus ional spreading utilizing the Monte Carlo methods. Some examples of dr op tracks for drops of different size are presented. Drops' tracks are very sophisticated, so that the relative position of drops falling in itially from the same point can vary drastically. In some cases drops' tracks diverge very quickly, in other cases all drops move within a t urbulent eddy along nearly the same closed tracks, but with different speed. The concentration of drop tracks along isolated paths is found in spite of the existence of a large number of velocity harmonics. It is shown that drops (aerosol particles) tend to leave some areas of th e turbulent flow apparently due to their inertia. These effects can po ssibly contribute to inhomogeneity of drops' concentration in clouds a t different spatial scales.