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Fundamental study of a submerged and non-submerged three dimensional jet impinging upon a normal plane




Tsuei, Yeong-Ging, author
Chao, Junn-Ling, author
Baldwin, Lionel V., author
Colorado State University, Engineering Research Center, publisher

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Part I, Axisymmetric boundary-layer of a jet impinging on a smooth plate: The flow characteristics of a radial wall jet formed by the normal impingement of an air jet on a smooth fiat plate have been studied. The mean velocity and the turbulence statistics for different orifice velocities and diameters were measured with a pitot tube and a hot-wire anemometer. Most of the measurements were made at ten vertical stations spaced at 6 in. intervals along a radius. The first station was twelve inches from the stagnation point. A particular form for the turbulent shear stress is proposed. Using the incompressible boundary-layer approximations and a similarity assumption, the momentum and continuity equations were used to derive expressions in the form of a n exponential decay for the peak radial velocity and a linear growth for the boundary layer thickness with respect to the radial distance from the center. The measured profiles of velocity and turbulent intensities were found to be approximately similar; thus, approximate universal functions were obtained by expressing U/(U sub m) ,√(U12)(U sub m), √(V12)/(U sub m) and √(W12)/(U sub m) (the relative velocity and turbulent intensities respectively) in terms of a non-dimensional vertical coordinate L = ʓ/(δ sub 0.5). The characteristic length (δ sub 0.5) was chosen as the height where U/(U sub m) = 0.5. The mean velocity profile of the inner boundary-layer does not follow the pipe wall law and only a limited region can be approximated by the logarithmic form. This is attributed to the effects of the highly turbulent flow within the outer layer of the wall jet which produces disturbances penetrating deeply into the inner boundary-layer. Consequently, a higher wall shear stress results in this wall jet flow than in ordinary two- dimensional boundary-layer flow. The wall s hear stress was found to be approximately proportional to the invers e square of the radial distance.


Includes bibliographical references.
Final report to National Science Foundation.

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Turbulent boundary layer


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