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

摘要

Longitudinal, one-dimensional turbulence spectra were measured behind a towed grid in dilute aqueous high-polymer solutions. Several types of hot-film flowmeters with constant-temperature bridges were used, with emphasis on quartz-coated, platinum-film sensors of conical shape. Measurements in water were consistent with wind-tunnel measurements. Cylindrical sensors were found unsuitable. The additives were poly(ethylene oxides), polyacrylamides, and guar gum. Concentrations of up to 137 ppm were used. The guar gum produced temporary suspensions which were not suitable for turbulence measurements because of high noise level. With the other additives, the sensor signal near the grid included a high-frequency component (called raggedness) which was attributed to temporary (or temporarily altered) inhomogeneity caused by the grid bars. Three types of spectral effects were the distortion due to raggedness, a greater experimental scatter near the grid in newly prepared solutions, and the predictable shift due to viscosity increase. (Author)