An experimental study of jet impingement is completed with the presentation of the measured turbulent characteristics of the circular subsonic jet and the heat transfer rates measured when this jet impinges normal to a flat plate. The data suggest that for impingement very close to the stagnation point, the heat transfer can be computed by applying a turbulent correction factor to the laminar value calculated for a flow having the same pressure distribution as that present in the impingement region. The correction factor is found to be a function of the axial distance and not of Reynolds number. Farther away, the measurements agree well with the heat transfer estimated using the method of Rosenbaum & Donaldson (1967). At large distances from the stagnation point, the heat transfer falls off in inverse proportion with the distance.The documentation of the turbulent jet flow field includes measurements of the radial and axial velocity fluctuations and their spectra, as well as the radial distribution of turbulent shear$\overline{w^{\prime}u^{\prime}}$. In addition, measurements of the turbulence near the stagnation point and the total pressure fluctuation at the stagnation point are presented.

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The radial pressure gradient in combination with either a positive or negative radial gradient of angular momentum makes possible the realization of two dynamically different flows. When the angular momentum gradient is positive, the flow is stable; when it is negative, the flow is unstable. Mean velocity, turbulence intensity, and shear correlation measurements were made in both cases. The one-dimensional streamwise energy spectra of the lateral and transverse turbulent velocities were also measured. The turbulent energy balances for both cases reveal that the dominant terms are the production of turbulent energy and its spacial transport by the turbulent velocities. The effect of the centripetal acceleration field is to inhibit the spectral transport of turbulent energy in the unstable case. The dissipation rates are an order of magnitude greater than the dissipation rates in the unstable case. The one-dimensional streamwise energy spectra display a (-5/3) dependence almost two decades long in the unstable case and one decade long in the stable case. Furthermore, the spectra reveal that the constant in the Kolmogorov form of the spectrum is not universal and that it depends on the ratio of the rate of production to the rate of dissipation of turbulent energy. In this study this ratio ranged from 1.5–27, and the values of the Kolmogorov constant varied from 0.4–2.4.

Two complementary, thin screens treated in the Babinet principle have one thing in common, the line of their edges. Employing the assumption that scattering of electromagnetic waves from a thin, conducting screen is solely from the elements of the edges, we have made a simple derivation of the Babinet principle in electromagnetic form. We needed to treat but one element of edge with the aperture and conductor interchanged. The factors which affect the amplitudes and phases of the electric and magnetic scattered wavelets reaching any point of observation from the common element of edge of the complementary screens are identical except for phase factors of 0° or 180° caused by polarization effects at the conducting edge. Symmetry conditions from electromagnetic theory yield those factors. We have illustrated the Babinet principle in electromagnetic form by tabularly expressing the scattered waves from two complementary half-planes. These results also were based on the assumption that scattering by a thin screen is solely from the edges.

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