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Liquids

Fill a container with water using scene.add_liquid, run it, and check how much liquid stays inside.

1. Put water in a cup

import alloy

scene = alloy.Scene(dt=0.01)
scene.add_ground()
scene.add_open_box("cup", inner=(0.04, 0.04, 0.05), wall=0.01, pos=(0, 0, 0))     # pos: centre of the bottom
scene.add_liquid("water", size=(0.032, 0.032, 0.032), pos=(0, 0, 0.03))
sim = alloy.build(scene)
print(sim.routes()["water"]["route"])

liquid_sph

The cup is static, 4 cm wide and 5 cm deep inside. The water is a 3.2 cm cube that starts at rest in it.

2. Run it and measure

sim.run(0.5)
pos = sim.state(["water"], world=0)["water.points"]
inside = (abs(pos[:, 0]) < 0.02) & (abs(pos[:, 1]) < 0.02) & (pos[:, 2] < 0.05)
print(len(pos), round(sim.liquid_volume("water") * 1e6), inside.mean().round(2))

512 33 1.0

The first number is the particle count and the second the simulated volume in millilitres. The third is the share of particles inside the cup walls: 1.0 means none spilled.

3. Check the run

print(sim.check()["ok"])

True

To fill a container from above, pour instead of dropping a block: scene.add_pour("stream", 2e-5, pos=(0, 0, 0.12)) streams 20 ml straight down from that point.

Keep in mind

  • Containers narrower than 24 mm are unreliable (details).
  • A block of liquid dropped from above splashes over the rim; a poured stream much less, with scene.add_pour (details).
  • Liquid touching cloth is very slow, and cloth takes up no water (details).
  • Heated liquid does not convect (details).
  • Liquid is slow on the CPU, so keep the particle count small while you try things out.

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