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Abstract:The jet in crossflow at very low Reynolds number (Re=100) with and without block is performed by means of large eddy simulation for the jet-to-crossflow velocity ratios (r) ranging from 1 to 3, and the corresponding flow characteristics are compared. The results show that the time-averaged particle trajectories of the jet are slightly changed if a block is presented, and the mixed vortices are weakened. The existence of the block also can accelerate the formation of stable counter-rotating vortex pair. At lower velocity ratio (r=1), the block has little effect on the jet in crossflow with a symmetrically positive and negative kidney shaped vortices. As the velocity ratio increases, the effect of block not only can generate an asymmetry of positive and negative kidney shaped vortices, but also it can reinforce the interaction between the positive and negative vortices in the jet in crossflow. The effect of block on the temperature field is also analyzed in detail.

Investigation of the classical and pulsating jet in crossflow (JICF) at a low Reynolds number (Re = 100) has been performed by the LES method based on varied velocity ratios (r=  1~4). Time-averaged particle trajectories are compared in the classical and pulsating JICF. The formation mechanism and the corresponding flow characteristics for the counter-rotating vortex pair (CRVP) have been analyzed. An unexpected “vortex tail” has been found in the JICF at higher velocity ratio due to the enhanced interactions indicated by the increased jet momentum among the CRVP, upright vortices, and shear layers. The analysis of time-averaged longitudinal vorticity including a coupling mechanism between vortices has been performed. The returning streamlines appear in the pulsating JICF, and two extra converging points emerge near the nozzle of the jet at different Strouhal numbers. The temperature profiles based on the iso-surface for the classical and pulsating JICF have been obtained computationally and analyzed in detail.

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