So I want to know what happens when granules are subjected to forces while around other varieties of granules. My interest comes from two places, wanting to gold pan, and how sand surfaces from dirt at the edges of buildings. It doesn't make too much sense to me right now, I'm just having a hard time imagining all the forces, and was never taught how to calculate drag and friction forces for fluids. So... im not so sure where exactly i should start. I know I have drag, friction, boyancy, density, volume, and gravity to calculate. Another thing is I don't know how to figure out how fast or far a turbulent force will go. Say... I have a cube stone in a flat river, how would the water react? If possible I would more like a place that will explain some of this stuff than bother everyone here with all these questions.