POLYDISPERSE GRANULAR FLOWS OVER INCLINED CHANNELS DISSERTATIONto obtain the degree of doctor at the University of Twente, on the authority of the rector magnificus, Prof. dr. H. Brinksma, on account of the decision of the graduation committee, to be publicly defended on Friday 9 October 2015 at 16:45 hrs by Deepak Raju Tunuguntla born on the 3rd of November 1986 in Hyderabad, India.
Granular materialsEverything seems simpler from a distance.
-Gail TsukiyamaMatter exists in a variety of forms, of which granular materials -although simplebehave differently from any of the other standard forms (solid, liquid and gas). For example, a sand castle appears like a solid, which when tumbled upon, crumbles down like an avalanche. On a few occasions, this avalanche takes down the whole castle, whereas sometimes it is confined only to a thin layer on its surface (liquid). In another example, shake up some crushed ice in a cocktail mixer and it behaves like a gas, whereas when trying to pour some salt out of an orifice of a jar, the flow tends to choke and gets clogged at the orifice. Granular material has it all, solid, liquid, gas, plastic flow, glassy, etc. -it can mimic all of these behaviours. Thus exhibiting a prime reason for investing our interest in understanding these simple but, mysterious materials.
HistoryOur knowledge of granular matter dates back to an era even before mankind's existence. These materials exist on a range of scales -micron sized to planetary -in a variety of forms, exhibiting multitudes of interesting phenomena. The earliest encounter between man and granular matter happened in the surroundings in which he evolved, i.e. with soil, sand, stones, rocks, etc., but more importantly it was his need for survival that ultimately led to an inevitable bond between humanity and granular matter, existing till today. Historical records indicate that primitive men often settled along the river banks where fresh food was available throughout the year. However, due to climatic changes coupled with migration of primitive tribes, new food gathering methods had to be devised. Man needed to find some way to store the nutrients for periods of time when no fresh food was available. Seeds, such as cereal grains, seemed to be one way to solve 1 1 2 Introduction Figure 1.1: Facsimile of a famous scene from a wall painting on the tomb of Djehutihotep, a pharoah (circa 1932(circa -1842. It illustrates his huge monolithic statue being transported from the quarries. In the front of the statue (near the feet) we see a workman pouring water to lubricate the sand, helping the four rows of workmen, 43 men in each, to haul the sledge smoothy (less friction). The figure is adapted from Dowson [1].the storage problems. Ultimately around 8000 BCE, during neolithic revolution, this seed storage led man towards becoming more agriculturally oriented. Grains were likely among the first cultivated crops. They could be grown relatively easily, farmed in surplus quantities and were suitable for storage in harsh cold winter climat...