Hello and welcome to the Babylon community!
The example you showed is using Particle Systems Particles | Babylon.js Documentation (babylonjs.com), so you could play with properties like the emitters, direction and speed to create an effect of flowing through a tube: Babylon.js Playground (babylonjs.com). @mawa also went in some great detail about this effect in a recent post: Make diffuseTexture move over mesh - Questions - Babylon.js (babylonjs.com)