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Effects of Repulsion and Attraction between Rotating Cylinders in Fluids

Relevance. From the theory of hydrodynamics, it is known about the interaction of a pair of vortices in inviscid fluids. The relevance of the study is conditioned upon the presence of many studies of numerical simulations of the interactions of two vortices or two cylinders, but the lack of research of practical installations for observing the effects of attraction and repulsion in fluid media may slow down research in this area for practical application.

Purpose. The purpose of this study is a practical demonstration of the possibility of the effect of double interaction in the air, with the calculation of the approximate magnitude of the force tending to attract or repel each of the cylinders.

Methods. In a practical experiment, a pair of plastic cylinders are used, which are driven by engines and rotate next to each other in the air at atmospheric pressure. Numerical simulation of the effect shows the nature of the effect and allows predicting the magnitude of the force generated by rotating cylinders on each other. The relationship between the directions of rotation of the cylinders and the observed effects was verified by numerical simulation using numerical simulation of finite volumes of OpenFOAM version 9.

Results. In a practical experiment, a pair of rotating cylinders started interacting at 5-7 cm in the experiment, which at a smaller distance of 2-3 cm created sufficient force to stabilise the vibrations of one of the cylinders around the thread for which it is suspended. Numerical simulation shows that a zone of high or low pressure is formed in the space between the cylinders, depending on the direction of rotation. The rotation of adjacent disks with opposite directions of rotation helps the circulation of the other cylinder to maintain the flow velocity in the gap, which reduces the fluid pressure between the rotating disks and attracts them. Conversely, rotating disks with the same direction extinguish and compress fluid flows in the gap, which increases the air pressure between rotating objects above the stationary pressure and repels them.

Conclusions. The results of the study provide a better understanding of the processes of fluid interaction, link the dependence of the interaction force on the parameters of the medium and cylinders, and demonstrate the practical possibility of applying the effects of interaction in fluid media