riparian rap

Modeling media research–the fine color coded fraction.

We’re continuing our research on low density modeling media.  The mix we usually use tapers out at around 0.5mm on the fine end, but clearly adding smaller particles has a big effect on behavior in movable bed models.  This fraction fills the interstitial spaces and strongly influences subsurface water movement.  And it increases cohesion to some degree.  It also clogs filters in our recirculating systems, which is one reason we’ve avoided it.  But we’ve been working with Emriver model users to develop a particle size mix that includes this finer fraction.

Today I worked on color.  Producing color-coded by size plastic media is a difficult and expensive process.  Our Em4 media has three sizes and colors (video here).  We want to add a fourth fine fraction.  The dark brown/white/yellow scheme we have now has a perfect chroma (brightness–very important for observation and photography/sensing) and very nice eye appeal (I’m a follower of Tufte on these things).  You can clearly see the differences in particle movement and deposited facies.

But it’s tough to move beyond these three distinctive, earthy tones.  We have some fine media in red and blue, and I tried those today.  Very interesting results!  At ~5% of each, mixed in the dry, you can’t see them at all.  But add a little water, and the sorting is amazing; they pop right out!  Red’s not so good, but maybe the blue will work.  But then we use blue and green dye for tracing–could be a conflict there.

Very exciting and promising.