Cross and clover shaped orifice jets analysis at low Reynolds number

• Main Authors: Meslem Amina, Nastase Ilinca
• Format: Article
• Language: English
• Published: VINCA Institute of Nuclear Sciences 2015-01-01
• Series: Thermal Science
• Subjects: clover jet; cross jet; switching-over; Entrainment; jet throw
• Online Access: http://www.doiserbia.nb.rs/img/doi/0354-9836/2015/0354-98361300166M.pdf

The jet coming from a cross-shaped orifice with an open center has been shown in the past, to provide substantial increase in the near field convective transport-mixing, in comparison to a classical round orifice jet. Detailed information has been reported in previous works on the role played in the jet mixing enhancement by the crow of vortices composed of counter-rotating pairs of secondary streamwise structures which are developing in orifice’s troughs. A trough in the cross-shaped jet generates a local shear like the one generated by a triangular tab in a square jet. In the present study we are interested by the modification of local shears in the troughs of the cross-shaped jet, when orifice geometry is modified, such as the center of the orifice becomes closed, leading to a clover-shaped orifice. The general motivation is to understand the effect of using a set of combination of longitudinal structures, themselves produced by the superposition of local shear regions, in mixing performance of a cross jet. It is shown that lower entrainment rates in the clover jet is a results of a additional internal crown of vortices which opposes the external one due to inner shears generated by closing the center of the orifice.