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## Studying the specific features of free rise of solid spheres in a viscous fluids at moderate Reynolds numbers

The paper presents results of numerical simulations of freely rising solid spheres in a viscous fluid. The

diameter of spheres was 5 mm, 7 mm, 10 mm, and 20 mm, and the corresponding Reynolds numbers

varies in the interval 1400 < Re < 10100. It has been found that the free rise path varies, as the

Galileo number increases. The paper describes the principal zigzag path generating mechanism, which

is determined by regularly generated and freed, oppositely oriented vortex structures, which carry away

the momentum and mass of fluid from a rising sphere. Quantitative characteristics are given with respect

to oscillation periods of a sphere path, transverse velocity components, and accumulation of fluid mass

involved in the attached vorticity. It has been found that the vortex detachment period is coincident with

the half-period of oscillations. A critical mass of a fluid in the attached vorticity has been calculated, and

a mechanism of changeover from zigzagging to spiraling has been suggested