An Experimental Investigation of Turbulence Mixing as a Factor in the Transportation of Sediment in Open Channel Flow

This investigation was conducted for the purpose of making a thorough study of the fundamental properties of the turbulence mixing process involved in the flow of water in an open channel. A channel 10 1/2 in. wide, 10 in. deep, and 40 ft. long was constructed in such a manner that illuminated globules formed by the injection of an immiscible fluid into the water could be photographed. A statistical analysis of the displacements of the globules from the origin yielded the intensity of turbulence and the correlation of successive velocities of a particle of fluid. Through these measurements of the intensity of turbulence and the correlation of velocities, the nature of the turbulence in open channel flow was determined. The results of the investigation led to the conclusion that similarity of diffusion exists throughout the vertical center line of open channel flow. Due to this similarity, the mising length may be proportional to the root-mean-square velocity fluctuation and the mixing coefficient proportional to the mean-square velocity fluctuation or energy of turbulence. The concept of a particle of fluid losing its identity in the surrounding fluid was found to be untrue for the flows investigated herein. This study was conducted under the direction of Robert T. Knapp, Associate Professor of Hydraulic Engineering, California Institute of Technology