Flow and diffusion calculation (ecosystem model)  Flexible boundary layer multi-level model

I was finally able to create a program that I thought would be nice to have something like this.
It is numerical analysis model that has been likely but not available until now. Based on an orthodox
planar two dimensional multi-level model, it can move boundary layers up and down according to the water
surface fluctuations, and at the same time, increase and decrease the number of boundary layers, and also
tilt boundary layers to match the slope of the river. It is a multi-level numerical analysis model that
can handle not only density flows, but also diffusion calculation in ecosystem models. I believe that
this will allow us to perform a three-dimensional analysis of water areas with large variations in water
depth, from the coast to estuaries and mid-stream areas including river floodplains.

The flexible boundary layer multi-level model Fbml_flow3 is a computational model that can change the number and height of boundary layers in the vertical direction, which has been fixed in the conventional planar two-dimensional multi-level models, as well as the gradient of the boundary layers.

This makes it possible to perform three-dimensional analysis even in water areas with large changes in water depth. Flow conditions, density diffusion, and substance diffusion (ecosystem model) can be performed not only for sea areas, lakes, and estuaries, but also for the middle reaches of rivers, from normal flow to flood flow. Here, a finite element method using a triangular mesh (unstructured grid) is used to discretize the equations.