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Title: Grid and pipe flow turbulence in polymer solutions
Author: Allan, John J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1978
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The structure of Grid-generated and Pipe Flow turbulence was measured in water and solutions of high molecular weight water soluble polymers. The effect of polyethylene oxide (Polyox grade WSR 301) on Grid-generated turbulence was investigated using laser anemometry and flow visualisation technique. It was found that the polymer additive reduced both the turbulent intensity and the rate of decay behind the grid. At typical drag-reducing concentrations, turbulent energy spectra were qualitatively the same as those in water, in agreement with the results of other investigations. However, at higher additive concentrations, the dissipation range spectra showed noticeable attenuation. This seemed to be a threshold effect with onset at a polymer concentration between 100 and 250 ppm. This result was supported by photographs of dye-injection tracer but in this case the onset concentration for small-eddy suppression was between 50 and 100 ppm. Polyox WSR 301 and a polyacrylamide (Separan AP 273) were studied in Pipeflow turbulence using laser anemometry. Mean velocity profiles did not follow "Virk's ultimate profile" but were well described by the model of Van Driest at conditions of less than maximum drag reduction. Turbulent intensity profiles were qualitatively in agreement with the results of others with higher values in the intermediate region than for Newtonian flow. Profiles of local dissipation rate were inferred from measurements of the energy spectrum. These indicated that dissipation is higher than for Newtonian flow in the intermediate region and lower in the turbulent core. The energy spectra showed a threshold concentration for non-Newtonian behaviour at lower concentrations than for Grid Flow. The spectra were modified significantly at all flow positions with small eddy suppression in all cases, the amount of suppression reducing with distance from the pipe wall.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available