flow in a pipe. The injection point was situated where the flow was welldeveloped. Thus, subsequent streamwise variations in pressure drop were due to the injected polymer spreading out across the pipe. The axial development of local drag reduction was monitored by a series of closely-spaced pressure tappings. The corresponding radial dispersion of the injected polymer, as it travelled downstream, was assessed by sampling the flow at various points.Local drag reduction, due to either point injection at the centerline or injection through a slot in the wall, was found to increase with distance downstream. This increase was related to the streamline increase of polymer concentration in a narrow annulus near the pipe wall. It was tentatively concluded that the effective annulus was bounded by 15 5 y + I 100, in agreement with previous deductions from less direct evidence.

Turbulent drag reduction produced by injection of polymer at the centerline of a pipe flow was found to increase with streamwise distance from the injection point. This was due to radial dispersion of the injected polymer. A tentative relationship between the two is proposed.

a pipe flow through either a small tube at the center line or an annular slot in the wall. The solution contained polymer at an injection concentration of 1, OOO wppm. Injection into water flow with a Reynolds number Re = 3.5 X lo4 was at a rate which gave a mean polymer concentration of 5.0 wppm in the water flow. A laser-Doppler anemometer (LDA) was used to measure the streamwise turbulent velocity at various radial positions and at several stations downstream from the injection point.Results were obtained for mean velocity and intensity profiles; autocorrelations; and one-dimensional energy spectra. The mean bursting period was determined using the "short-sampling-time" autocorrelation method. Changes in all these quantities due to polymer injection were found to depend on the amount of local drag reduction at that particular downstream station but were independent of the local polymer concentration at the measuring point.

No abstract

Due to the huge applications of the sand-water slurries in nature and industry, the importance to study the sandwater flow increased. In this paper, the turbulent flow of sandwater slurries is experimentally studied in a closed-loop pipeline system in the laboratory. The experiments are utilized to show the effect of the variation of both the sand diameter and the sand concentration on the two-phase pressure drop and the two-phase friction factor by changing the Reynolds number and the sand volume concentration. The pressure drop is increased along with the Reynolds number.In the experiments, three different sand diameters are used at different three concentrations with water. The diameters of the sand are 0.15, 0.3 and 0.44 mm, while the concentrations of the sand are 2.5%, 5% and 10%. The experiments show that the pressure drop and the friction factor are increased with increasing the sand diameter and the sand volume concentration. Furthermore, the pressure drop is increased for high mixture flow rates.