A granular material is a conglomeration of discrete solid macroscopic particles such as sand, snow, coffee, rice etc. which under certain conditions can flow. There are many industrial applications such as transport of coal, grain, powder, salt etc.
A debris flow is a moving mass of a mixture of mud, sand, soil, rock, and water that travels down a slope under the influence of gravity. To be considered a debris flow, the solid material must be consisting from sand-size particles or larger at least in proportion as50%. There are fast debris flow in areas of steep slopes or very slow.
For modelling all flows (water flow, granular materials flow or debris flow) the constitutive relation namely the relation between stress and strain rate is required which is different for the above-mentioned flows.
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Thanks Dr. David
There is plethora of literature talking about granular flows but for debris flow is limited. As i plan working on debris flow, i want to make sure that i am reading right articles.
As per my understanding and your answer, i believe debris flow is a subcategory of Granular flows But they are different in there behavior.
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I agree with the answer of Ioan David . It provides a good definition and gives an imagination of the differences, which might be required in the modeling treatment for the both different kinds of flows.
A granular flow is essentially a mixture of a granular (particle) material and one fluid - the latter might be e.g. air or water. Examples are e.g. circulating fluidized beds or sand transport in river beds.
An example for debris flow might be e.g. a mud slide on a hill face, where sand, gravel and stones of different sizes are premixed to the mixture of clay, mud and water. Other flows of similar kind might be named as debris flows as well. Consequently the model description of this kind of flow is much more difficult in comparison to a granular flow, because the relationship for the acting stress tensor and the governing viscous forces might e.g. widely depend on the water content of the debris flow and ranging from a plastic, highly-viscous and rather creeping (low velocity) flow behavior to a rather water-like and more Newtonian flow behavior. The presence of a whole spectrum of particle/debris sizes over several orders of characteristic diameter range adds an additional degree of complexity.
Regards,
Dr. Th. Frank.
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