# How cant I increase fluid particles velocity, over time?

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Hi;

In a particle fluid simulation, I add velocity using "point vop". The problem is the particles start to move very fast from beginning, but I want they start to move by ease.

How cant I increase particle's speed (velocity), over time?

Thanks.

Fluid_Velocity.hip

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pop wrangle plugged in to "particle velocity" on the flip solver...

v@v *= fit(@Frame, 1, 24, 0, 1);

This will multiply your velocity on a ramp from 0-1 between frames 1 and 24.

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7 hours ago, woodenduck said:

pop wrangle plugged in to "particle velocity" on the flip solver...

v@v *= fit(@Frame, 1, 24, 0, 1);

This will multiply your velocity on a ramp from 0-1 between frames 1 and 24.

It doesn't work.

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instead of feeding initial velocity from SOPs, use POP Force DOP or other forces

force acts on velocity every timestep, therefore it will keep gradually increasing your particles velocity

you can also add some POP Drag or POP Wind to introduce some air resistance to not accelerate forever

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Hi "anim",

The problem is I want to assign a fix, velocity noise to points, and when I use noise in a Dop, "POP VOP" node, it changes noise over time. I just want to scale velocity over time.

Edited by Masoud
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then you can store your already computed v that you are happy with into some temporary attrib like v@tmpv using Attribute Swap SOP, method: Move

and in DOPs use POP Wrangle: v@force = v@tmpv * chf("weight");

it will use your v@tmpv vector (further scaled by weight parm) as a force

since force is added to velocity each timestep it will naturally accelerate, so just adjust weight to control the rate

Edited by anim

Thanks.

Edited by Masoud

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