Function generate_bout_grid 

pub fn generate_bout_grid(
    psi: &Array2<f64>,
    r_axis: &[f64],
    z_axis: &[f64],
    psi_axis: f64,
    psi_boundary: f64,
    b_toroidal: f64,
    config: &BoutGridConfig,
) -> FusionResult<BoutGrid>

Generate a BOUT++ field-aligned grid from a 2D equilibrium.

Takes the poloidal flux ψ(R,Z) on a rectangular (R,Z) grid and traces flux surfaces to build field-aligned coordinates.

Arguments

• psi — Poloidal flux on (nz_eq, nr_eq) rectangular grid
• r_axis — R coordinates of the equilibrium grid [nr_eq]
• z_axis — Z coordinates of the equilibrium grid [nz_eq]
• psi_axis — Flux at the magnetic axis
• psi_boundary — Flux at the separatrix/boundary
• b_toroidal — Toroidal magnetic field at geometric center [T]
• config — BOUT++ grid configuration