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Published June 2005 | public
Journal Article Open

Impinging laminar jets at moderate Reynolds numbers and separation distances


An experimental and numerical study of impinging, incompressible, axisymmetric, laminar jets is described, where the jet axis of symmetry is aligned normal to the wall. Particle streak velocimetry (PSV) is used to measure axial velocities along the centerline of the flow field. The jet-nozzle pressure drop is measured simultaneously and determines the Bernoulli velocity. The flow field is simulated numerically by an axisymmetric Navier-Stokes spectral-element code, an axisymmetric potential-flow model, and an axisymmetric one-dimensional stream-function approximation. The axisymmetric viscous and potential-flow simulations include the nozzle in the solution domain, allowing nozzle-wall proximity effects to be investigated. Scaling the centerline axial velocity by the Bernoulli velocity collapses the experimental velocity profiles onto a single curve that is independent of the nozzle-to-plate separation distance. Axisymmetric direct numerical simulations yield good agreement with experiment and confirm the velocity profile scaling. Potential-flow simulations reproduce the collapse of the data; however, viscous effects result in disagreement with experiment. Axisymmetric one-dimensional stream-function simulations can predict the flow in the stagnation region if the boundary conditions are correctly specified. The scaled axial velocity profiles are well characterized by an error function with one Reynolds-number-dependent parameter. Rescaling the wall-normal distance by the boundary-layer displacement-thickness-corrected diameter yields a collapse of the data onto a single curve that is independent of the Reynolds number. These scalings allow the specification of an analytical expression for the velocity profile of an impinging laminar jet over the Reynolds number range investigated of 200<=Re<=1400.

Additional Information

©2005 The American Physical Society (Received 7 June 2005; published 14 December 2005) We would like to thank D. Lang for his contributions to the digital-imaging in this work, as well as G. Katzenstein for his assistance with experimental design and assembly. R. D. Henderson and H. Blackburn provided considerable assistance, as well as the codes that our axisymmetric viscous simulation code is based on. The work was funded by AFOSR Grant No. F49620-01-1-0006 and the DOE Caltech ASC Contract No. W-7405-ENG-48, whose support is gratefully acknowledged.


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