Formation of Water Rings Around a Rotating Centroid in Oil

In a tank filled with water at the bottom and oil floating on top, a straight rod reaching into the oil is set to rotate. The rotating rod is brought just above the oil/water boundary and is set to rotate at a speed greater than 200 revolutions per minute. It became evident that the rod’s rotation caused the oil/water interface to curve upward around the center of rotation, reaching up to the bottom of the rotating rod. Visible rings of water formed around the rod, starting at the bottom (at the oil/water interface) and ascending the rod, one by one. The water rings remained separate and ascended the rod until they eventually dispersed into the oil. Such quantization of water into rings has never been reported on before and represents a novel area of investigation in fluid dynamics. This study aims at obtaining quality photographic evidence to explain this phenomenon.