While this is not an FRC related topic, I know many people here have much more experience in this than I do (I have not yet taken any mechE courses), and I figured I would ask here as well as somewhere like engineering stack exchange.
I am attempting to simulate the optimal nozzle geometry to shoot pressurized water to act as a carrier for debris (through water as a medium). I would also like to simulate how debris would travel after being knocked off of a surface by a rotating drum. Is there any easy way to do this, or am I better off just designing and prototyping until I get close enough?
I don’t think I understand exactly what you’re trying to do, but from what you’ve described, there’s no “easy” way to model this. Multiphase flow gets weird pretty quick.
I’ve used this nozzle vendor before. Their catalog has a lot of good guidance on nozzle selection and backing calculations to determine the right one. That might be helpful, or at least show you what’s commonly available.
Interpreting empirical results from prototyping is likely a viable path to finding some of the answers you seek.
ETA: researching “slurry flow” in an industrial context might be helpful too.
Essentially I’m trying to use a jet of high pressure water to carry debris/particulate through water, instead of using something like a vacuum on the other end. Makes sense that it’s not an easy problem. Is there any way to split it into two parts, like this?
Model the high pressure water through standing water
Model the debris through high pressure water
I was thinking of just doing empirical prototyping for most of the development of this system, and just doing the math to make sure I’m approaching something optimal. If that isn’t possible, I might just do math for the simpler things (like the nozzle) and use my empirical data to fill in the rest.
You may want to talk to your nearest professor of Fluid Dynamics.
Take a look at the course catalog, find an intro to fluids class, figure out which professors teach that, and their office hours. You probably won’t understand all the math right away, but you should be able to get put on the right track, and/or get access to fluid simulation software.
Honestly, even if I can’t take a class in it for another couple of semesters (prereqs ) I still might reach out and ask some questions about just the general idea and how it might end up working. Cold emailing with a university email is way better than cold emailing as a high schooler, I will say.
I wouldn’t be so sure about that, and I surely wouldn’t let it stop me from emailing. Worst case, you get no response as a high-schooler, which is the exact same outcome if you don’t email at all, so you’ve got very, very little to lose.
(I also think a lot of profs would find it inherently motivating to respond to an eager high-schooler.)
The higher velocity stream with debris is within the volume of water you’re trying to convey through? I’m not sure that will work. What I’m envisioning looks like a jet mixer. In the chemical world we use this concept to mix and homogenize the contents of a tank.
Well thankfully I don’t have to worry about it now. It would be even better if I was officially in the mechanical engineering department, but undeclared engineering is good enough.
Consider it like a fume extractor, but instead of a vacuum of air and the particles being in air, its a jet of water with the particles being in water.
If you’re already in college, office hours, in person, attend. Knawmsayin?
If you get blown off, whatever. In my experience, though, office hours can be pretty effective as to getting answers, and as someone who isn’t in the class but is interested I suspect the prof would help–if nothing else you’re more likely to take their section when you are able to take that course.
If the prof doesn’t have time they may pass you to a TA. TAs can be just as helpful sometimes.
I would highly recommend that you look into a venturi tube to help pull the water. To model this you need a program to do computational fluid dynamics (CFD modelling). Most programs are not cheap, but you may be able to find someone with that capability at your school. I have some experience with them to model tank agitation and mixing. Very cool, but very complex mathematics.
Somewhat yes, in that I am trying to use water as a medium to carry the debris. However the junk coming off the roller is definitely larger than micron scale. If necessary, I could probably preprocess the debris to make it easier to carry, but as the particle gets smaller, it gets harder to filter out on the other end.
To explain in a bit more detail (maybe), I have to get debris from inside a static water medium up to the surface, where I then clean the water and store the debris. My main issue here is figuring out the best method to get the debris to the surface of the water. I could use suction, but that would probably take a lot of power, which is why I settled on trying to use jets of water. If you guys have any better solutions to that problem more broadly, I would love to hear them, I have not settled on anything yet.
Regardless, I would encourage you to research industrial water/wastewater filtration. This is a well-explored realm of engineering with lot of really clever solutions that could be applicable to your problem.
Compute the Reynolds number and see what types of equations you ought to look at. Laminar, transitional, or turbulent?
Compute drag forces on the particle sizes you work with. Is the drag force enough to overcome gravity or other forces fighting what you want to do?
Compute flow development lengths and shear rates in the channels you’re looking at. Is the boundary layer smaller than your smallest particle?
Do it all by hand, then set it up in a spreadsheet or Matlab and play with he numbers until you get numbers that seem sane. Do the flow rates, duct sizes, and such seem possible?
It would take a long time, dozens of hours at least, to model something like this accurately in multiphase cfd. Or you could spend a couple hours doing hand calcs and make a scale model with flow similitude and check things out empirically.
) I still might reach out and ask some questions about just the general idea and how it might end up working. Cold emailing with a university email is way better than cold emailing as a high schooler, I will say.
% of the shots you don’t take…