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Oblique collision and reconnection of a vortex ring with a vortex tube

Oblique collision and reconnection of a vortex ring with a vortex tube

The oblique collision and reconnection of a vortex ring and a vortex tube are numerically investigated using a sixth-order accurate vortex-in-cell method. At the oblique collision angle (*α*) of 0°, the reconnection occurs, in which half of the ring joins with a part of the tube to create a reconnected ring, and another half of the ring links to the rest of the tube to establish a new reconnected tube. At *α* = 15°, 30°, and 45°, two reconnections take place, where the first one generates a distorted reconnected tube, and then this tube reconnects itself to construct a new ring and a tube. The secondary vortex structures only appear surrounding the reconnected ring at *α* = 0°, while they are around both the reconnected ring and tube at *α* = 30° and 45°. As *α* increases, the time interval *τ* between two reconnections rises, and it is determined by a quadratic function as 𝜏(𝛼)=0.0037𝛼^{2}+0.0853𝛼+0.975. The energy spectrum of the flow at the wavenumber (*k*) from 3 to 10 obeys the 𝑘^{−5/3} slope of a fully turbulent flow, and it is independent of *α*. However, the energy spectrum at the high wavenumber from 10 to 60 depends on *α*. This energy spectrum approaches the 𝑘^{−5/3} slope after the second reconnection for whole investigated cases.