INSTABILITY PROPERTIES OF INTERACTING JETS

Two parallel circular jets, in inviscid incompressible how, with unifo rm axial velocity of the same magnitude and direction are placed near to one another, resulting in a strongly coupled field. A given (small) wavenumber in the axial direction is taken and a dispersion relation is found relating the frequency and wavenumber for a given disturbance mode, along with the velocity potentials within and exterior to the j ets. The problem is tackled analytically using bipolar coordinates and asymptotic forms for the dispersion relation are found in the small-s eparation and large-separation limits. Results are then compared with the corresponding two-dimensional problem for plane jets. It is conclu ded that close-proximity interactions greatly destabilize the varicose mode of the coupled jet, and greatly stabilize the sinuous mode.