Скачать или смотреть 4K SPH Python+Taichi. 100K particles. Merlin 1a engine horizontal test. Better nozzle. Real noise.

For this new year 2025 :
Another 4K SPH simulation of an Horizontal test of a Merlin 1a engine from SpaceX, with many start/stop... and the real noise of the Merlin 1a.
This time, the combustion chamber and nozzle are created using Taichi's mesh function, making a much more realistic engine made of real sheet metal and particles.
You can compare with te previous one :
   • 4K SPH Python+Taichi. 100K particles. Merl...  
The engine still becomes hot when it is running.
Compared with the previous simulation, I fixed a small bug (a second one... !) concerning reflex rebound calculations in the nozzle. The jet generated by the nozzle is now more concentrated, which better reflects actual jet engine behavior.
This simulation is the most difficult I've ever done, because you have to know what to do with particles that have a high velocity. They are inside the nozzle at program step n, but outside at step n+1. We do a test to detect it, in order to make the reflexive bounce (taichi.maths.reflex)... like a ball could do against a wall. Very good, except that now the particle is outside as if it had passed through the wall of the nozzle (or combustion chamber)... just as a quantum particle might do !
So I had to find a way of bringing it back inside without it being visible to the viewer of the video, who would otherwise see the propellants coming out of the nozzle or chamber on all sides. I simulated a repositioning inside the nozzle “as if” the program could have made one or two intermediate steps/loops between the steps n and n+1.
Gauges : From up left to the right :
Level of filling of reaction chamber
Temperature in chamber
Start/stop light
Below the reactor left to right :
Flow speed at exit of chamber
Flow speed at exit of nozzle
Thrust at exit of nozzle
Simulation written from scratch, from nothing, only with the languages Python and Taichi. Taichi is extremly fast and powefull because it knows how to use the garphic card (here Nwidia RTX 4060).
The display is done with Taichi
SPH means smoothed particle hydrodynamics, it is a meshfree particle method based on Lagrangian formulation, and has been widely applied to different areas in engineering and science.
Video edited to add a soundtrack and improve the resolution to 4K by CapCut.