STUDIES ON TWIN NONPARALLEL UNVENTILATED AXISYMMETRICAL JETS

Twin non-parallel jet configurations occur in many practical devices l ike burners, combustion chambers, and also in the area of fluidics etc . Despite the importance of such configurations, studies on the intera ction of twin non-parallel jets are very limited. The present work is an attempt to investigate the mixing of two axisymmetric jets obliquel y oriented towards each other. Experimental studies were made on the i nteraction of twin intersecting axisymmetric jets issuing from two unv entilated convergent nozzles. The nozzles of exit diameter (D) 10 mm w ere set on a common end wall with their axes intersecting each other a t half angles (alpha) of 0 degrees, 5 degrees, 10 degrees and 15 degre es. The centre-to-centre spacing (S) of the nozzles, non-dimensionaliz ed, as S/D, was 3.1. The jet exit Mach number (M(c)) studied was 0.2. The results indicate that the near field characteristics are strongly influenced by alpha. However, the potential core of the individual jet s and the far field characteristics of the twin jet flow field, that i s beyond downstream distances of 40 nozzle diameters, are not signific antly influenced by alpha. The cross-section of the jet just downstrea m of the combining point is approximately elliptic. The axis switching phenomenon normally associated with non-circular jets is observed in the jet flow field. The spread of the combined jet is more in the tran sverse direction than in the spanwise direction. Entrainment of the am bient fluid is found to be more in the case of twin parallel jets (alp ha = 0 degrees). The entrainment decreases with increasing alpha. The self-preserving nature of the combined jet is almost independent of th e initial geometric conditions. The combined jet is axisymmetric with regard to the normalized velocity and length scales.