How can I simulate granular flows in Gazebo?

Hi, I am trying simulate a sand pile made by 1000 spheres in gazebo, which requires a lot computation time. To make it runs faster, I am considering use GPU-accelerate physics engine, PhysX, as a plugin in Ignition physics. For now, I am reading this page as start, but not sure if it will work well. Can I have some suggestion on this?
Otherwise, I also have an idea that just creating a fluid simulation plug-in like this Bus apparently the Fluidix doesn’t support anymore. How do you simulate fluid in Gazebo nowadays?