The dynamics of the near field of strong jets in crossflows

摘要: An inviscid three-dimensional vortex-sheet model for the near field of a strong jet issuing from pipe into crossflow is derived. The solution this shows that essential mechanisms governing idealized flow are distortion main transverse vorticity by generation additional axial and within owing to pressure gradients induced external flow, convection both components upwind side its downwind side. deformation cross-section which predicted compared with commonly used time-dependent two-dimensional model. Differences arise because latter does not take account effects transport component vorticity. complete leads symmetrical no overall deflection in direction stream. To viscous effects, initial region uniform modelled as an entraining vortex sheet, acts like sheet vortices sinks, redistributing bounding shear layer inducing non-symmetrical deformations croas-section jet. This stream, loci centroids cross-sections describe quadratic cur+e. Deformations each three models measurements obtained photographs air emerging wind tunnel. Mean velocity around made hot-wire anemometer agree theory ; they clearly invalidate jets based on 'pressure drag'.