Showing papers by "Young I. Cho published in 1984"
TL;DR: An in-vitro flow study was conducted in a mildly atherosclerotic main coronary artery casting of man using sugar-water solutions simulating blood viscosity, finding both pulsatile and steady flow data from the casting to be nearly equal to those from a straight, axisymmetric model.
Abstract: An in-vitro flow study was conducted in a mildly atherosclerotic main coronary artery casting of man using sugar-water solutions simulating blood viscosity. Steady flow results indicated substantial increases in pressure drop, and thus flow resistance at the same Reynolds number, above those for Poiseuille flow by 30 to 100 percent in the physiological Reynolds number range from about 100 to 400. Time-averaged pulsatile flow data showed additional 5 percent increases in flow resistance above the steady flow results. Both pulsatile and steady flow data from the casting were found to be nearly equal to those from a straight, axisymmetric model of the casting up to a Reynolds number of about 200, above which the flow resistance of the casting became gradually larger than the corresponding values from the axisymmetric model.
66 citations
TL;DR: In this article, the authors used the falling-ball experiment to measure the non-Newtonian viscosity in the intermediate shear rate range of a polyacrylamide solution.
Abstract: An attempt to use the falling-ball experiment to measure the non-Newtonian viscosity in the intermediate shear rate range was successfully accomplished by combining the direct experimental observations with a simple analytical model for the average shear and shear rate at the surface of a sphere. The viscosity data of aqueous solutions of Carbopol-960, carboxymethyl cellulose, polyethylene oxide and polyacrylamide obtained from the falling-ball viscometer gave good agreement with those from other viscometers, confirming the general applicability of the analytical approach. In the experiments with the highly viscoelastic polyacrylamide solutions the terminal velocity was observed to be dependent on the time interval between the dropping of successive balls. This time-dependent phenomenon was used to determine characteristic diffusion times of the concentrated solutions of polyacrylamide. These values were, in turn, compared with characteristics relaxation times determined by the Powell-Eyring model. The experimental program revealed that the falling-ball viscometer has very limited utility for the measurement of the steady shear viscosity of aqueous polymer solutions.
54 citations