Dear Respondents,
State of forces acting on the typical sand particle due to water erosion is represented in the figure. Where of particle W, cohesive force FC, the angle of internal friction and resistance force FR . comment on them. If you find any fault kindly give your comments.
check if the cohesive force that acts between the particles representation is correct/wrong?
Resistance force, FR= given in the linked file,
Figure is given in word file attached
Thank you
Dear Velusamy, sum of forces is ok; but why is internal friction so defined? Is water erosion from top or from left? Perhap it could be useful for you the sand dunes discussion on Ian Stewart, "What shape is a snow flake?". Gianluca
Dear Velusamy,
There are 3 ways that grains can move: 1. lifting of the grain off the grains beneath it. 2. sliding of the grain up and out of its position on the bed. 3. rotation of the grain about a pivot point formed by neighboring grains
For case 1, lift forces must exceed the “gravity force” (i.e. the weight, since gravity itself is an acceleration) For case 2, drag forces in the direction of easiest movement must exceed the combined frictional and gravitation force in the opposite direction For case 3, the moment of the fluid forces must exceed the moment of the gravitational force.
Fluid force is the resultant between lift component and Drag force.
http://www.sfu.ca/~hickin/FLUIDS/Chapt6-Sediment%20transport.pdf (Page 6.19)
With my best regards
Prof. Bachir ACHOUR
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