An Experimental Study of Grid Turbulence in Dilute High-Polymer Solutions

摘要

The aim of this study was to determine the effects upon the longitudinal, one-dimensional energy spectrum in grid turbulence of the non-Newtonian properties produced by low concentrations of high molecular weight polymers dissolved in water. By studying an approximately isotropic turbulence, in which the experimental effects of the non-Newtonian properties of the solution might be most easily correlated with theory, it was intended to contribute to the eventual understanding of the mechanism of the friction reduction which the test solutions typically show in turbulent shear flows in pipes and boundary layers. A 48-foot towing tank, with cross-section of 48 by 45 inches, was constructed and equipped for grid-turbulence measurements in water and aqueous solutions and suspensions. The experimental procedure was to tow a vertical grid along the tank, followed by a turbulence sensor moving at the same speed as the grid. The grid was towed at a standard speed of 36.2 cm/s. The grid form was chosen to allow a correlation of the results in water with grid turbulence measurements in air. The mesh width was 11.8 cm. The grid Reynolds number, RM, was roughly 40,000 and the turbulence Reynolds number, RL, was about 500.