It has been mentioned in the literature that the Jet spread Rate (Ku ,which gives the measure of the mixing or entrainement ) for laminar jet is more than that of the Turbulent Jets. But its a common concept that mixing is more enhanced when the flow is turbulent. So is that concept not applied to JET FLOWS?
Turbulent flows are characterized by having greater influence of inertial forces to viscous forces, then even greater lateral diffusion spreading is smaller.
Turbulent flows are characterized by having greater influence of inertial forces to viscous forces, then even greater lateral diffusion spreading is smaller.
The jet spread rate is related to the entrainment from the lateral boundaries. The entrainment rate is significant when the flow is laminar (or low Re) when there is not enough mixing. If the Reynolds number at the jet exit is greater than a few thousand, the entrainment in the jet is then constant, therefore the radial spread of the mean velocity field and the decay of the mean centerline velocity in the downstream direction are independent of Reynolds number.
Probably the lateral entrainment at the jet boundaries depends on the the local turbulence intensity, which is affected by the shear stress between the layers. Shear stress is higher in laminar flow compared to turbulent flow. Additional turbulence is generated due to the instability of local shear stress that enhances the mixing/ entrainment. For turbulent flow we refer to average turbulent intensity and not local one. For more information check studies on shear flows and mixing.
May be because transverse component of velocity which is responsible for lateral spread of laminar jet is more predominent than turbulent jet.
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