Looking for Recomendations -- High Pressure Waterjet Fluid Simulation


One of the major reasons I have started learning blender is to be able to do High Pressure waterjet simulations. If you are not familiar with high pressure waterjets, it is a device that cuts material (Steel, rock, foam, ect) with high pressure water. (bear with me for a second)

For all intents and purposes, water comes out of a nozzle, hits a work piece, then that work piece dissolves away (Thus cutting the material).

I am interested in using Blender to help me simulate this. What I would like help with is a general design of such a simulation.

What I have in mind (and I’m not sure if this is feasible or possible) is a Fluid simulation in combination with the Blender Game engine. The water flows out of the nozzle hitting the work piece. Using something like the fracture tool and the game engine, very small particles are then dislodged and removed - thus creating a cut.

However, I’ve played quite a bit with the fracture tool, and haven’t been able to get much use out of it with >50 shards. Realistically, I’d probably need the particles to be rather small (and therefore be numerous).

Does this seem like a good design for a simulation? Any other better recommendations?

What I have in mind (and I’m not sure if this is feasible or possible) is a Fluid simulation in combination with the Blender Game engine.
The fluid sim does not work in the game engine.

You could experiment with dynamic paint. You could make the water affect the alpha of the material being cut and create a partical system that spews out shards as it cuts. I would love to see a video of this in action if you complete it! Hope this helps!

This is why I ask. Thanks :slight_smile:

This is an intriguing solution. I presume you mean something like this youtube video, except obviously with transparency instead of orange paint. There is one issue with this - I need the water to exit by moving through the cut area - not rebounding back up.

(continuation of last post to include a second link…apparently I can only put one link in at a time. I’m not a spammer, I promise)

I do not think the partial system that spews out shards would be necessary for two reasons. Firstly, waterjets remove material in very small particles (think about the size of a grain of sand) and I’m not aiming for precise detail, just a nice little animation to describe some of the research we are doing. The first ten seconds of this youtube video give a little bit of an idea of what I am shooting for (not exactly, but close), and the rest gives an idea of what actual cutting looks like.

BTW, I really appreciate the help guys. :slight_smile:

I suggest watching this video by Blender Guru:http://www.blenderguru.com/videos/how-to-create-realistic-rain
He shows you how to kill the particals once the touch the surface.

You may want to use a volumetric material and then section it

I appreciate all the help thus far.

I’ve put much time into attempting to get this done to past two or three weeks, and though I’m not getting too far on this, I am learning a lot about blender in the meanwhile. One possible solution I’ve found is Displacement painting by MiikaHweb.



Even though it wouldn’t cut through the material, I think I could make this work for me. However I am having trouble finding a tutorial. Anyone know of one?

Could you elaborate on this a little? I’m not sure how this would help me.

I watched the whole thing, and it is a very well put together tutorial. I specifically noticed the rain disappearing thing you mentioned.

I have tried to get dynamic paint to paint alpha so to speak, however as far as I know, I can only paint it a non-transparent color. Do you have any pointers how to do this?

Again, I really appreciate it.

In real life, can you even see particle fly off? I don’t think you can see the water jet hitting the work peace even. The nozzle is too close and it is under water! What are you trying to show?

Depends on the specific application. Usually the answer is not really.

The most important thing I am trying to show is the toolpath (basically the motion of the nozzle as it moves).

We have some complex motions (using up to 5 axes) for the toolpath that we were having trouble explaining in presentations – a simple animation would be so much easier to use – literally we had a 20 minute conversation trying to explain the concepts once. I’d like to make it a one or two minute explanation.

Currently I have figured out a way that would work using dynamic paint (without the alpha channel thing - haven’t figured that one out yet). Though it doesn’t look very good (and by “doesn’t look very good” I mean terrible), and would not work if I decided to extend my animations to a third dimension. So I’m looking for a more powerful solution.

Probably the way to go is to show how cutting head tilts. And show water jet cutting geometry in section, close up, in slow motion. The fine cutting action is too fast for the eye to see. You know, more illustrative approach then fluid simulation.

This is exactly what I am trying to do. :slight_smile:

I’ve decided to create two simple animations to demonstrate. I think my issue will be much more clear after watching these. I made these pretty quickly, so this is not nearly a finished product. Additionally, the tool path is kinda random.

The first video has no sort of water interaction with the work piece. The water just flows through:

The second I add dynamic paint to paint a path. This is much more clear to understand what is going on, as it helps present a history of where the nozzle has been. However it looks terrible:

I don’t think anyone is confused, but just in case I made the animations to clarify a little better. I would like to improve the blue path to more closely resemble a cut (I could make a better blue line with dyanmic paint, but it will still look bad).

I’m also open to changing my method entirely, for instance if a particle system would work better.

Maybe cheat and have the shapes “pre-cut” but assembled very closely prior to the animation starting, then you can use dynamic paint to peel the outer layer of each object away from the jet as it passes along the seam.

Once its done cutting you could make the leftover piece fade to transparent so your audience can see the finished result.

I already understand your axes of movement from your animation.

An article today on blender nation about advances with the boolean svn’s

Just found that. It looks really cool. I may explore that in the future – specifically if I can’t get my script working. :spin:

This is almost exactly what I have decided to do. Because the pieces are so small in order to make this look realistic, it took me about 45 minutes to do a small section. (Key framing and what not). So I am in the process of writing a python script that will automate this for me.

However, I’m not sure how to make dynamic paint fade to transparent, or peel the outer layer – though I don’t think I need it.

In the process a question has popped up. Is it possible to control the speed at which an object moves? After a simple animation, you’ll notice that the object has an acceleration phase and a deceleration phase. For my animation to work, I’d have to figure out a mathematical model of the acceleration/deceleration sequence, or specify a flat velocity. Anyone have any tips on this?