3D printed laminar flow nozzle for very stable water jet output

I'm trying to make a very stable, laminar flow. I don't want the flow to visibly move, so let's say less than 0.1mm of movement. I want laminar flow as it is optically very satisfying. In this video I show you the third (fourth? I lost count) iteration in trying to do so.
In this version, I use a 3D printed laminar flow nozzle. It consists of an adapter (to fit the tube), a section with very small flow channels (created by the infill pattern of the 3D printer), and a nozzle with a thin top with a small opening in it. Also, between the pump and the nozzle is a pressure vessel (a balloon in a yoghurt pot). In the previous iteration, I saw a lot of pressure variations; the pressure vessel should even this out.
For the Python script for computing the Reynolds number, see my website: elexperiment.nl/2023/05/3d-pr...

[@icepicknz]

Thanks for your video, I just posted a make on your thing :)

[@kloppertje]

Nice! Do you have a link?

[@AdityaMehendale]

A "sharp" winglet can help to cleanly detach the flow from the tube. I can imagine that an abrupt and massive "end-cap" would aid in this direction. Perhaps a hydrophobic coating too.

[@pieterjanvanderstoel946]

It looks like the nozzle isnt too stable. So if there is pressure variation in the hose, the nozzle will respond to that with slight movement. Increasing the stiffness of the nozzle mount could reduce the movement of the laminair water flow.

[@kloppertje]

Thanks, will try it in the next iteration!

[@lordsandy]

Could you please share the 3d design files for all the components. I want to make a more smaller version of the nozzle.

[@WalkerAlldredge]

Any chance you’ll share the STL files?

[@kloppertje]

The STL is very simple: it's just a cylinder, and the mesh is the infill generated by the slicer :)

[@nusretalikok823]

Hello! Might I ask if you calculated the reynolds number without the infill, as a normal cylinder, or with it? If you calculated it with that patern, are there and formulas you could direct me to?
**Just saw your website and the python code, looks great! Just one question, there are more than 30 holes in the geometry, so why is the nStream varibale set to 30?
Assuming the nStream variable is for the rectangular sections, I edited your code as follows, feel free to let me know what you think
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import math
# Compute Reynolds number for different flow configurations
# flowRateLperH = 500 # [l/h]
flowRateLperH = 757.082 # [l/h]
flowRate = flowRateLperH/3600 / 1000 # [m^3/s]
hoseDiameter = 0.014 # [m]
hoseArea = (hoseDiameter/2)**2 * math.pi
flowSpeed = 1 # [m/s] just to have set a value
flowSpeed = flowRate / hoseArea
# print(flowSpeed)
kinematicViscosity = 0.8927E-6 # [m^2/s]
# Now compute for N smaller streams
# Idea: split a stream into N smaller streams
tubeDiameter = 40E-3 # [m]
tubeArea = (tubeDiameter/2)**2 * math.pi
fillFactor = 0.7 # Some surface area is lost due to wall thickness
print ('Tube Area', tubeArea, '[m]')
lineDistancing = 2E-3
cubeArea = (lineDistancing)**2
print ('Cube Area', cubeArea, '[m]')
nCubes = tubeArea*fillFactor/cubeArea
print ('Number of cubes', nCubes)
nStream = nCubes
streamArea = cubeArea
streamDiameter = math.sqrt(streamArea/math.pi)*2
flowSpeed = flowRate / (tubeArea*fillFactor)
Re = flowSpeed*streamDiameter/kinematicViscosity
print('Tube diameter %.3f [mm]' % (tubeDiameter*1e3))
print(nStream, ' streams with diameter of %.3f [mm]' % (streamDiameter*1e3))
print('Reynolds number [-]: ', Re)
# Compute entrance length
# turbulent flow
# laminar flow
entranceLengthLam = 0.0575*Re*streamDiameter # laminar
# entranceLengthTurb = 1.359*streamDiameter*Re**0.25 # turbulent
print('Entrance length [m]: ', entranceLengthLam)
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I really liked the project btw, kudos!

[@kloppertje]

Hi there! Thanks for your elaborate comment and the compliments. The approach taken for calculating the area per rectangular cross-section sounds good. I don't remember exactly why I used nStream=30, probably I was just experimenting. One remark is that the computation for the reynolds number might be different for a circular and a rectangular cross-section, but this you'd have to look up somewhere. I've forgotten most of my fluid dynamics courses ;)

[@kekovskigeronimothehero8514]

@@kloppertje Thanks for the reply! Im glad the 30 value was just experimenting, took me a long time to figure out why it was there. As for the reynolds number, yeah there is a separate equation for rectangular cross sections, but I cant figre out the wall thickness of the infill so I cant calculate it. Im a fourth year mech. eng. student, and this project is really helping me out so thanks again!

[@nusretalikok823]

Hello again @kloppertje ! I'm currently working on a design project for my course at school and Im using a similar design to the nozzle you have in your videos. I've also modified the python code to better fit my project. I just wanted to thank you again for both the video and taking the time to answer my previous question regarding the python code! Its been nice virtually meeting you, and I hope you have a wonderful rest of your day :)