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Old 01-09-2019, 08:42 AM
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maxxkatt maxxkatt is offline
Join Date: Sep 2015
Location: North Atlanta, GA
Posts: 1,740
Default sink rate and fluid dynamics

I think it is a combination of densities of the medium, eg wet or saturated soil and fluid dynamics. But then I am not telling you anything that others are saying here.

The more wet or saturated the soil the faster the sink rate of objects with the same orientation and density.

Denser objects will sink faster that less dense objects in the same state of saturation.

The orientation of the coin will affect the sink rate. Say you have two 1964 silver quarters say six inches apart and the saturation of the soil is the same and of course the density of the quarters are the same.

But one quarter is laying perfectly horizontal to the surface and one inch from the surface. The other quarter is buried one inch from the surface and six inch to the left or right of the first quarter but is in a vertical or 90 degree angle from the horizontal surface. Or to put it another way is perfectly on its edge.

There is more resistance to sinking with the flat coin than the vertical coins. Simply because it is easier for the water soil mix semi-fluid to get out of the way of the vertical oriented coin because much less surface is presented to the underlying soil/fluid mix than the coin laying flat. The coin laying flat has the most resistance to the soil/fluid mix from moving away from the coin.

So you vary the coin orientation and density of coins you get a variety of results. Thus a lighter coins say a zinc penny in a vertical orientation can easily sink faster than say a buffalo nickel in a flat orientation.

The trouble is unless you dig all of them out still in the plug where you can see their orientation relating to the surface you cannot see how they were orientated in the soil.

I am sure there is someone experienced in fluid dynamics and calculus could puzzle out a formula, but that does not change what and where we find them in relation to depth. We just go out and hunt and find the coins the best we can.

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