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Viscous region of turbulent boundary layer: technical report




Tieleman, H. W. (Henry W.), author
Fluid Dynamics and Diffusion Laboratory, College of Engineering, Colorado State University, publisher

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The nature of mean and turbulent motion in the viscous sublayer of a thick boundary layer with zero pressure gradient has been investigated. Measurements have been made of the mean motion, two of the turbulent velocity components, the turbulent shear stress, and spectra of the longitudinal component of the velocity fluctuation. Traverses were made through approximately one-fifth of the boundary layer, which was approximately 32 inches thick. The boundary layer was developed along the floor of the wind tunnel test section for 85 feet. The turbulent shear stresses and the turbulence intensities were evaluated from a single rotated wire. A detailed account is given of the theory concerning the yawed wire operation. Included are corrections for the results from normal and yawed hot wires when operated in large mean velocity gradients and/ or turbulence intensity gradients. By assuming local similarity, the semilogarithmic velocity distribution can be derived. However, when local similarity is assumed it is required that aU T/ax= 0 or that aT/ay = 0 in the region where the law of the wall is valid. The measurements confirm the existence of a constant sear-stress region near the wall. However, the results show that the constant shear layer does not exist as far out as where the semilogarithmic velocity distribution is valid. Cross-checks were made between mean flow measurements, turbulence measurements and wall shear-stress measurements. The results were compared with existing theories for boundary layer flow near the wall. Energy spectra of the streamwise turbulence component indicate that the theory of local isotropy can be applied to turbulent shear flows. This is especially true when the boundary layer is allowed to develop for a relatively long time. Measurements indicate that √v2 is much closer to √u2 in magnitude as compared to the results from small scale boundary layers. This study was made in connection with a program which intends to give criteria for the modeling of atmospheric boundary layers in the wind tunnel.


December 1967.
Includes bibliographical references (pages 117-120).
U.S. Army Research Grant DA-AMC-28-043-65-G20.

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Turbulent boundary layer


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