Numerical study of the interaction of vortex ring and background turbulence

Abstract

The article presents the results of direct numerical simulation of a turbulent vortex ring with a moderate Reynolds number, interacting with the field of external turbulent fluctuations. The ring is formed by buoyancy forces from a spherically-shaped volume of elevated temperature. We consider the interaction of the ring with the field of turbulent fluctuations (of temperature and velocity) located in the form of a horizontal layer in front of the ring. The effect of separation of vortices by the sign of vorticity in a layer of fluctuations (with respect to the rotation of the ring) during the passage of the ring through this field has been found. This effect first causes the ring to slow down when the fluctuations pass outside the ring, and then to accelerate with decreasing radius when the fluctuations pass through its center. Due to buoyancy effects in the fluctuations layer, the separation of hot and cold air occurs. During the interaction with the ring, this leads to the accumulation of the reduced temperature in the core of the ring, while the increased temperature is accumulated near the axis. This temperature distribution results in a baroclinic vorticity generation leading to the reduction of the ring radius.