Some Rheological Properties of a Diluted Gelatin Aqueous Solution in the Turbulent Flow Region. I

Abstract

The rolling ball method was used to study rheological properties of gelatin solution. The motion of a stainless steel ball in a slanting glass tube filled with the solution was observed. In order to attain turbulent flow, we chose the ball of 1.113 cm diameter and the tube of 1.650 cm diameter. The achievement of the turbulent flow condition was checked from the theoretical and experimental points of view.The terminal velocity of the ball in the 0.5% aqueous solution of gelatin exceeded that in water when the slope of tube exceeded 64°. Whether the ball was rolling or sliding in this region was examined by taking multiple exposure photographs, using the ball marked with a small piece of fluorescent adhesive tape. At the beginning the ball was rolling normally. Soon the sliding was combined with rolling, the rate of rotation gradually decreased, and then the rotation completely stopped. Finally, the ball rotated in reverse direction. Such behavior was never observed in pure water. The possible causes of this unique phenomenon were discussed. This may be one mode of appearance of the Toms effect of gelatin.