Viscosity influence on the stability of a swirling jet with nonrotating core

The effect of the viscosity on the linear stability of a swirling top hat j et with nonrotating core is studied analytically. Numerical values of the g rowth rate are obtained. It is shown that the viscosity induces instabiliti es in the region of wave numbers where no inviscid instability occurs. In t he short wave limit, the asymptotic solution reveals that the situation is quite different for the strictly inviscid and the viscous cases. While in t he inviscid fluid the growth rate is proportional to the wave number, in th e viscous case the growth rate approaches a constant value for large wave n umbers. (C) 2000 American Institute of Physics. [S1070-6631(00)00405-0].