Test Fixture and Lessons Learned

A project log for Display Squared

A display that puts on a display. Images are created using colored water that's precisely jetted through the air into a 100 x 56 pixel grid

zachfrewzachfrew 06/14/2021 at 00:360 Comments

The goal of building a test fixture was to prove out the fluid jetting concept and sanity check my math in the physical world. The test fixture involves the pressure vessel mounted on the actual load cell I plan on using. I attached a tube and nozzle to the quick release fitting, and I tested how far the water traveled for different fluid heights. I would show you this process, but it was fairly messy and I've only got a few hours left to submit this to the rethink displays contest.

So what did I learn? As expected, there are losses in the system. The fluid travels less far than I was expecting by what looks to be a factor of around 25%. This isn't particularly concerning. I was expecting loss due to turbulent flow effects and friction. This error will be easy to compensate for by increasing the fluid height. 

That said, the turbulent flow causes a more significant problem, albeit one that is solvable. As the stream exits the nozzle, it rather quickly increases in diameter and turns into more of a spray. It was naïve of me to expect that the jetted water would maintain a consistent diameter at the furthest extents of the display. It appears that the stream is breaking apart at a distance of around 150mm, which isn't going to cut it for this project. 

This is solvable by modifying the nozzle geometry, but I'm sure it's going to take some iteration. My working theory is that turbulent flow effects are having the largest effect on stream length currently, so that's what I'm going to tackle next.