Home > Legacy archive > Specific versions > FARGO-2D1D > **Overview**

Here are the new parameters to activate in your parameter file to perform a run with a 1D grid. They are the inner and the outer radius of the 1D grid.

For example :

If `Rmin1D`

> `Rmin`

, the 1D grid is only present outside the 2D grid, from `Rmax`

to `Rmax1D`

.

If `Rmax1D`

< `Rmax`

, the 1D grid is only present inside the 2D grid, from `Rmin1D`

to `Rmin`

.

If `Rmin1D`

> `Rmin`

and `Rmax1D`

< `Rmax`

, an error message comes and the code exits.

In fact, `Rmin1D`

is determined by the code. The rings width is given by `Rmin`

, `Rmax`

and `Nrad`

. Then, the smallest possible inner edge radius larger than the input `Rmin1D`

is chosen. Symmetrically, the largest possible radius smaller than the input `Rmax1D`

is chosen for the outer edge of the 1D grid. A message is output :

`IINNER`

is the number of rings between the inner edge of the 1D grid and the inner edge of the 2D grid ; it can be negative if the 1D grid is only present outside the 2D grid. `NRAD1D`

is the total number of rings in the 1D grid.

If `NRAD1D`

is larger than the maximal size of the 1D grids, `MAX1D`

(defined in types.h to be 16384), an error message appears and the code exits.

### Important remark :

The 1D grid is not a subsitute for the 2D grid. Therefore, the limits of the latter (`Rmin`

and `Rmax`

) should not be modified with respect to a run with the standard version of FARGO.

If the interface between the two grids happens to be too close to a planet, the disk evolution through the interface may not be smooth.