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. doi:10.7907/6ZYC-HJ88. https://resolver.caltech.edu/CaltechETD:etd-09152005-133021

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

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 10⁵, 3.08 x 10⁵ and 6.16 x 10⁵, 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 v', w' 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 Τ 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 Ly, Lz and micro-scales of turbulence λy, λz across the channel are presented and their variation with Reynolds number is discussed. Using a new technique, values for λx were obtained; a method for estimating Lx is also given.

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

Thesis Files