分野別セミナー

An analytical model which describes the global time evolution
of an axisymmetric vortex ring is considered. The suggested
model provides not only a good prediction of ring’s integral
characteristics but also a more accurate description of the
vortex ring topology compared with the classical Norbury-Fraenkel
model. Generalizations of the model make it possible to predict
the ring' integrals of motion at high Reynolds numbers, assuming
that the Reynolds number effect can be modelled by taking into
account the elliptical vorticity distribution (instead of a
conventional circular form), and to predict the turbulent vortex
ring's properties, assuming the time dependence for the vortex
ring thickness in the form
L=at^b (a is a positive number and
1/2 ¥le b ¥le 1/2 ), coupled with the time dependent effective
turbulent viscosity L L'. The applications of the model to the
vortex ring-like structures in gazoline fuel sprays, to optimal
vortex ring formation and to flapping flight of birds and insects
are dicussed.