The region near the nozzle exit of laminar free jets is of interest to those involved with the design of fluid control and free jet sensing devices often applied in low cost automation. An experimental and analytical investigation of an axially symmetric, laminar free jet with an initially parabolic profile has been carried out in the region close to the nozzle for jet Reynolds numbers of 168 and 290. Solutions using Andrade and Tsien’s theoretically derived expression for the virtual origin of an initially parabolic jet an compared with measurements and with numerical solutions of the boundary layer equations. It is shown that numerical solutions give good predictions of the velocities in the axial direction within 1 to 20 diameters from the nozzle and that the classical solution gives inaccurate predictions within 1 to 9 diameters from the nozzle even after the expression for the virtual origin has been adjusted to correspond more closely is measurements in the far region of the jet.

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