Normally-Impinging Jet from a Circular Nozzle

Experiments by Cooper et al., and Baughn et al.

Description

The experiments provide an extensive set of measurements of a turbulent jet impinging orthogonally onto a large plane surface. Two Reynolds numbers have been considered, 2.3 × 10⁴ and 7 × l0⁴, while the height of the jet discharge above the plate ranges from two to ten diameters, with particular attention focused on two and six diameters. The experiment for the velocity field was designed so that it provided hydrodynamic data for conditions the same as those employed by Baughn & Shimizu when measuring heat-transfer rates. Before discharge, the air passed along a smooth pipe sufficiently long to give fully developed flow at the exit plane of the jet: a feature that is helpful in using the data for turbulence-model evaluation. Hot-wire measurements have been made with inlet pipes of nominally one-inch (26 mm) and four inches (101.6 mm) diameter. Data are available of the mean velocity profile in the vicinity of the plate surface and also of the three Reynolds-stress components lying in the x-r plane. Computational results reported in Ref. [4] indicate a good degree of internal consistency between the mean and turbulent field data in that models predicting the mean flow poorly (or well) also predict the turbulence data poorly (well).

Inlet and Boundary Conditions

As noted above, at the pipe exit, the flow should be fully-developed. In computational work, it is suggested that an initial calculation should be done to generate fully-developed pipe flow profiles at the apprpriate Reynolds number, which can then be used as inlet conditions for the impinging jet computation.

The outlet plane should be placed at a sufficiently large radial distance that errors arising from the application of zero-gradient (or similar) conditions will not significantly affect the region of interest. For the present measurements (extending to around r/D=6), it is suggested that the outer radial boundary should be at r/D=8 or greater.

The boundary opposite the impingement wall is a surface across which fluid in entrained. One common method of dealing with such boundaries (in pressure-correction based finite-volume solvers) is to impose ambient pressure values at the boundary, and to allow fluid to be entrained at the rate necessary to satisfy continuity in the boundary cells.

Measurement Techniques

Available Measurements

Reference and Previous Solutions

References and Related Publications