Initial mixing of inclined dense jet in perpendicu

Authors: Chris C K Lai Joseph H W Lee

Publish Date: 2013/06/05

Volume: 14, Issue: 1, Pages: 25-49

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Abstract

A comprehensive experimental investigation for an inclined 60circ to vertical dense jet in perpendicular crossflow—with a threedimensional trajectory—is reported The detailed tracer concentration field in the vertical crosssection of the bentover jet is measured by the laserinduced fluorescence technique for a wide range of jet densimetric Froude number Fr and ambient to jet velocity ratios U r The jet trajectory and dilution determined from a large number of crosssectional scalar fields are interpreted by the Lagrangian model over the entire range of jetdominated to crossflowdominated regimes The mixing during the ascent phase of the dense jet resembles that of an advected jet or line puff and changes to a negatively buoyant thermal on descent It is found that the mixing behavior is governed by a crossflow Froude number mathbfF = U r Fr For mathbfF 08 the mixing is jetdominated and governed by shear entrainment significant detrainment occurs and the maximum height of rise Z max is underpredicted as in the case of a dense jet in stagnant fluid While the jet trajectory in the horizontal momentum plane is wellpredicted the measurements indicate a greater rise and slower descent For mathbfF ge 08 the dense jet becomes significantly bentover during its ascent phase the jet mixing is dominated by vortex entrainment For mathbfF ge 2 the detrainment ceases to have any effect on the jet behavior The jet trajectory in both the horizontal momentum and buoyancy planes are well predicted by the model Despite the underprediction of terminal rise the jet dilution at a large number of crosssections covering the ascent and descent of the dense jet are wellpredicted Both the terminal rise and the initial dilution for the inclined jet in perpendicular crossflow are smaller than those of a corresponding vertical jet Both the maximum terminal rise Z max and horizontal lateral penetration Y max follow a mathbfF1/2 dependence in the crossflowdominated regime The initial dilution at terminal rise follows a S sim mathbfF1/3 dependence

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