USING CONTROLLED UNSTEADY FLUID MASS ADDITION TO ENHANCE JET MIXING

A rectangular jet was excited by controlled unsteady fluid mass additi on using two miniature fluidic jets placed on either side of its narro w dimension. The subharmonic of the primary's preferred jet column fre quency [St(D-e) = fD(e)/U-J = 0.15] was forced in the antisymmetric mo de because such forcing persists for longer downstream distances than the fundamental. Details of the phase-averaged flowfield, velocity gra dient terms, velocity spectra, and the mean and fluctuating flowfields were documented. The fluidically excited mode grew and persisted in t he flow beyond the potential core region. Unsteady fluid mass addition of 12% (4% momentum addition) per fluidic jet resulted in a 35% reduc tion of the potential core length and about a 60% increase in the norm alized mass flux (percentages are with reference to the primary unforc ed jet). On the basis of the results, it appears that fluidic devices have the potential for use in shear flow control applications.