I am interested to know whether the forces that cause brownian motion can help keep larger particle suspended in a fluid even though they are too large to show the movement.
I belive that there always be some drag due to gravity and Brownian motion would not change that. Upon time averaging things would look as a steady downward motion, a fall. This is a situation with water aerosols I work with. Regards. Jerzy Klimkowski
Thanks for your response. Is there any mathematics that supports the idea that the forces causing the brownian motion would have a buoyant effect to keep the particles in suspension for longer than if they were not present. I'm not a physicist (or mathematician!) and am unclear whether the random forces from all sides would have this buoyant effect. Would the object fall quicker if the suspension were colder?
In general the Brownian motion is but sort of oscillations about the equillibrium point, or a steady path, so upon applying time averaging, this effect should zero out. However there are two things that come into play, so the entire picture changes. Using the term "Brownian motion" you mean random movements of particles w/o referring to any equillibrium or steady path, as these are unknown to you. Secondary blood, if not all body fluids, is everything but a newtonian fluid. It has a memory. So such a fluid remembers (just to ilustrate this) that this particle was "going left", although it now "goes to the right". I do not believe this would effect the action of gravity force per se, but in combination with "crowding out of heavier particles" under action of a cetrifugal forces in same body of the mixture, this could produce an apparent buoyant force. My insights may be very limited from this point on, because I have no experience with non-newtonian fluids. There is a group in the UK called FOAM, they deal in advanced comoutational fluid dynamic and may already have some software to lead you further on. RGDS. Jerzy Klimkowski
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