Rain Drop Motion in an Atmosphere Containing Aerosols Particles

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Abstract

A mathematical model is constructed for the dynamics of a raindrop moving in a gravity field through an atmosphere containing fine particles, taking into account the processes of relaxation of its velocity and the capture of fine particles. It has been established that the equation of motion of a drop in the problem posed belongs to the class of singularly perturbed equations, for the integration of which it is necessary to involve special algorithms. In the limiting modes of droplet motion, analytical solutions of the problem are obtained that describe the dependence of the droplet velocity and coordinate on time. In the complete formulation, the solutions of the problem are obtained numerically for different values of the defining parameters. The influence of the droplet size on the parameters of its motion in a concentrated aerodispersed mixture has been studied. The dependences of the limiting volume fraction of the solid component in the composition of the drop and the intensity of the precipitation of particles (washed out by the drop) on the earth’s surface on the size of the drop are obtained. Comparison of the calculated, approximate-analytical and experimental dependences of the steady-state rate of fall of a drop on its size was carried out, which showed their good agreement.

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About the authors

T. R. Amanbaev

Auezov South Kazakhstan University

Author for correspondence.
Email: tulegen_amanbaev@mail.ru
Kazakhstan, Tauke khan avenue, 5, Shymkent, 160012

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Supplementary files

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2. Fig. 1. Dependence of the steady-state velocity of a raindrop falling in the air (under normal conditions) from its diameter. Solid curves: 1 – calculation according to equation (9), 2 – approximate analytical formula [Ingel, 2012]. The dashed line is an experiment [Mason, 1971]. Dotted lines: 1 – Stokes mode (formula (7)), 2 – Newtonian mode (formula (8)).

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3. Fig. 2. Dependences of the modulus of the velocity vector of the raindrop on the vertical coordinate for different initial diameters of the drop: curve 1 – 125, 2 – 250, 3 – 500, 4 – 1000 microns. Dashed lines – absence of particle capture (but presence of lateral flow), dashed dotted lines – absence of lateral flow (but presence of particle capture).

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4. Fig. 3. Droplet trajectories at different initial diameters: curve 1 – 250, 2 – 500, 3 – 1000 microns.

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5. Fig. 4. Dependences of the total drop time and the distance of the drop from its size: 1 – , 2 – .

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6. Fig. 5. Dependences of the maximum volume fraction of aps, the volume of Vps of the solid component in the droplet composition and the intensity of particle deposition on the earth's surface qps on the droplet size: 1 – aps, 2 – Vps, 3 – qps.

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