Coherent Structures in Circular and Non-Circular Jets in Crossflow

Mixing in Circular and Non-circular Jets in Crossflow

“…The global maxima of the scalar may lie, however, off the centerplane [28]. They may be as much as one nozzle diameter below the penetration implied by the maxima in the symmetry plane [25]. This is due to the large-scale mixing effect of the CVP.…”

“…In the current experiment and computation, the jet from the blunt square nozzle penetrates less deeply compared to the diamond-shaped nozzle case. As the AR and nozzle shape are identical for both nozzles, the effect of bluntness is clearly revealed: Blunt nozzles have a stronger recirculation zone and produce more turbulence [25]. This decreases the jet penetration.…”

“…This qualitative difference is the result of the competition between small-scale turbulent mixing and large-scale mixing due to the CVP as is suggested below using proper orthogonal decomposition (POD). The nozzles producing one peak have elevated turbulence levels [25]. The CVP and the jet (the mean scalar region) meander with larger velocities in the turbulent flow field.…”

“…As discussed in Section 1, the trajectory of the deflected jet is a parameter of paramount importance with respect to mixing. One can define several characteristic curves for a JICF which have been called trajectory [15,25]. Two such curves are the mean streamline from the center of the nozzle and the so-called "vortex line", the locus of points with maximum upwash between the two vortices of the CVP, following Fearn and Weston [26].…”

“…This is of course not feasible at present as the computer power is excessive [27]. The trajectory data in the literature shows significant spread, which only partly can be attributed to varying definitions [25]. Other important factors are boundary layer thickness, jet velocity profile [11], geometric differences [12] and turbulence levels.…”