Browsing by Author "Picologlou, Basil F."
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Item Biofilm development and associated energy losses in water conduits(1979) Zelver, Nicholas; Characklis, William G.; Bedient, Philip B.; Picologlou, Basil F.Microbial film development in water conduits causes pronounced increases in fluid frictional resistance and heat transfer resistance which is of major concern to the water supply and power industries. The objective of this study was to better understand the microbial film development process and its effect on fluid frictional resistance. A Tubular Fouling Reactor system was constructed to investigate microbial film development in the laboratory. Glucose was used as the energy source for microbial growth. Fluid frictional resistance in the fouled tube increased to as much as eight times the clean tube condition. Constriction of the tube due to the microbial film does not significantly affect fluid frictional resistance. However, viscoelastic properties and the filamentous nature of the microbial film contribute to the increase in fluid frictional resistance. Growth kinetics and substrate removal were investigated and a model for microbial film production was developed. Experimental data were used to test the validity of the model and good agreement was obtained. The results indicate that fluid frictional resistance and microbial film thickness can be predicted from influent glucose concentration for a given flow velocity.Item Hydraulic evaluation of filter screens for power plant water intake(1979) Kamata, Masahiro; Walker, William F.; Beckmann, Herbert K.; Picologlou, Basil F.An investigation has been performed of hydrodynamic losses through filter screens used in power plant water intakes. For the experimental phase of the investigation, screens with aspect ratio up to 3.8 were tested. The Reynolds number range for the test was from 15-1 and the ratio of traveling screen velocity to water approach velocity varied from -1.. It was found that the characteristics of flow through slot mesh screens are similar to those for flow through square mesh screens. The losses through round wire screens can be estimated from the approach water velocity, wire diameter, and a function of the ratio of opening area to frontal area of the screen. If a finer screen mesh is desired for filtering purposes, slot mesh screens sustain smaller hydrodynamic losses than square mesh screens because the ratio of openings is larger. It was also found that the screen motion in the water could be easily simulated. It was determined that the losses for a traveling screen are the same as those for a stationary screen of the same design so long as the normal component of the approach velocity remains unchanged.Item In-vitro hydrodynamic evaluation of aortic valve protheses(1976) Lim Cheng Chye, Lawrence; Picologlou, Basil F.; Walker, William F.; Chimoskey, J. E.A mock circulatory loop was designed for the hydrodynamic evaluation of aortic valve prostheses. It had features of low priming volume (1 to 1.2 liters) and its fluid was protected from direct contact with air. The prostheses were mounted in the anatomic subcoronary position of a plexiglas model of the human aorta. Four commercial valve prostheses were tested in the loop in one case with the sinuses of Valsalva intact and in another case in the absence of the sinus cavities. They were the Lillehei-Kaster pivoting disc, Bjork-Shiley tilting disc Smeloff-Cutter caged ball and the Starr-Edwards caged ball valves. Tests were conducted at heart rates of 6 and 9 beats/minute and the aortic flow rates of 4 and 6 liters/minute. A valve performance index was formulated, based on the energy dissipation that occurs in flow through a valve. This dissipation coefficient, as it was called, was shown to be a fair, consistent means of rating valve performance. The results showed that the pivoting/tilting disc valves were superior in performance to the caged ball valves in terms of the mean pressure gradients across the valve, percentage backflows and energy dissipations recorded. The valves also functioned more efficiently in the straight tube section than in the section with sinuses. Plausible explanations were offered, based on the flow dynamics of the valves and their relation to the immediate geometry. The results of this work were compared with those of other investigators. Although no direct comparisons were possible because of differences in flow conditions, valve sizes and flow chamber dimensions, approximate comparisons showed fair consistency.