Hey, so i'll just start this by saying that any/all info i present here may be wrong, i've only got physics 20 under my belt right now but i've been doing a ton of research, so if i seem like i don't know what i'm talking about, it's because i probably don't. I'm in grade 12, and i'm interested in fluid dynamics, so i figured i'll build a water tunnel in my spare time. I figured it couldn't hurt, i could probably use it as a project for Phy. 30 and then i can use it later on in university, maybe do some tests with it, hey? But if i'm gonna do this, I wanna do this right. Take ALL Variables into account, and i mean everything. This is definitely something i want to be able to use, and possibly to let other people use as at least a semi-legitimate experiment source. I was thinking of possibly using a fish tank as the main flow chamber, haven't figured out what size yet though. i was thinking of using either small sections of PVC pipe glued/caulked to the inside of the tank or something along those lines as a honeycomb baffler, and i'm willing to spent the time filing them to round the trailing edges if you think that would give a more laminar flow, although i know for sure that i'm going to be using slow flow speeds (i don't know what these would be though. if anyone has any recommendations for a good slow baseline...?). I was toying around with a 2 pump/2 tank system, one pump for water and one for (possibly?) oil, which i was thinking of using as a visualization medium if it wouldn't create turbulence b/c of the different densities? after the flow observation tank i was thinking of having either a large section of PVC pipe or a thick section of hose (possibly 2 hoses, depending on the rate of flow through them and what would cause the least turbulence) connecting the main tank to a second holding tank where the oil would (hopefully) collect on the top of the tank where a second/third smaller hose with a pump attached would move the oil to a series of hoses or possibly something smaller (plastic syringe needles?) sealed into the inside of the tank which would distribute the oil into the laminar flow inside the main tank to act as a visualization medium, as mentioned above. A third/fourth hose sealed to the bottom of the holding tank would pump water into a large section of PVC pipe connected to the front of the main tank, starting the system over. This might seem unfeasible, if so please tell me because i don't want to get halfway through building this only to figure out that it won't work/won't work as well as i want something i built to work, but i THINK that if i can match the flow rate of the oil pump with the flow rate of water/oil mixture coming into the holding tank, i can keep a fairly constant fluid level in both tanks. My main problems/questions are: Will any oils work as valid visualization mediums, and if not then what will, other than dyes or styrofoam pellets? ( I don't want to mess around with the filters in the pumps TOO much). If oils will work, will there be any KH instabilities cause by the differing densities of oil/water? and are there any obvious flaws with this design or anything that you think i could improve in it? If you managed to read this far, thank you SO MUCH for your time, i know you'll be a huge help to me in this build. Either leave a comment or message me if you're interested in helping me out. Thanks again.