Supersonic single impinging jet flows are well studied and are known to exhibit strong unsteadiness levels, especially when resonance dominates. However, much less is known about the unsteady characteristics of two such jets operating in tandem, such as those in the F-35B aircraft, where flow unsteadiness is also influenced by jet-jet interaction and coupling. Therefore, flow-field associated with a pair of identical underexpanded jets at Nozzle Pressure Ratio (NPR) 2.65, discharged from identical converging nozzles with exit diameters 25.4 mm each, and impinging normal to a surface is investigated. Comparisons are made with a single impinging jet operated at identical conditions by contrasting the features seen in shadowgraph flow visualization, nearfield acoustics and surface pressure measurements on the ground plane. Strong unsteadiness levels, feedback mechanism that drives resonance and the corresponding instability mode shapes, are some of the similarities seen between the single and dual impinging jet configurations. Increased low frequency unsteadiness and a substantial reduction in the strength of axisymmetric instability modes in the case of dual impinging jets are also observed. Further, the fountain flow generated between the two jets is found to play an important role in affecting the unsteady characteristics in dual impinging jets.
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