Investigation of turbulent flow in a two-dimensional channel

Citation

Laufer, John (1948) Investigation of turbulent flow in a two-dimensional channel. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09152005-133021

Abstract

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A detailed exploration of the field of mean and fluctuating quantities in a two-dimensional turbulent channel flow is presented. The measurements were repeated at three Reynolds numbers, 1.23 x 10(5), 3.08 x 10(5) and 6.16 x 10(5), based on the half width of the channel and the maximum velocity. A channel of 5" width and 12:1 aspect ratio was used for the investigation.

Mean speed and axial fluctuation measurements were made well within the laminar sublayer. The semi-theoretical predictions concerning the extent of the laminar sublayer were confirmed. It was found that the viscosity has a more profound influence on the fluctuations than on the mean velocity, the region of influence being approximately four times as wide.

Fluctuations perpendicular to the flow direction [...] and the correlation coefficient [...] were measured, and the turbulent shear distribution calculated. Shear calculations from independent methods using the measured velocity gradient at the wall and pressure gradient along the channel furnished a good check on the values of the shearing stress in all cases with the exception of the highest Reynolds number where [...] obtained from the fluctuation measurements is approximately 25% lower. All mean fluctuating quantities were found to decrease with increasing Reynolds number. Measurements of the scales [...], [...] and micro-scales of turbulence [...] across the channel are presented and their variation with Reynolds number is discussed. Using a new technique, values for [...] were obtained; a method for estimating [...] is also given.

The energy balance in the turbulent flow field was calculated from the measured quantities. From this calculation it is posssible to give a descriptive picture of turbulent energy diffusion in the center portion of the channel cross-section.

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