SPINS resize

Matlab functions which change the resolutions of a simulation with spectral accuracy. The resolution can be increased or decreased. These exist in the SPINSmatlab toolbox.

Returns either a resized field within a live matlab session, or saves resized fields to a new subdirectory.

Assumptions

Applicable for:

• 2D (in the x-z plane) and 3D data
• free-slip and periodic boundary conditions

Chebyshev and mapped grids are not available, but this will not be too hard to implement should the need arise.

Resize a single field in one dimension

The following files return a matlab array.

• resize_x.m
• resize_y.m
• resize_z.m

Usage

These functions require 3 input arguments (in order):

1. field name
2. field data
3. new resolution

Example:

rho_new = resize_x('rho', rho, 512);

will return the array, rho_new, with an x-resolution containing 512 (whether this was larger or smaller than the initial size is unimportant).

If no spins.conf exists, or a general matrix is to be resized, then an optional argument can be passed. The optional argument must be a structure containing the type of expansion and the length of the dimension. The general matrix must satisfy the listed boundary condition.

Example:

opts.type_x = "FREE_SLIP";
opts.Lx = 1.0;
rho_new = resize_x('rho', rho, 512, opts);

Resize all fields for a particular output

The following files save resized fields for a particular output in a new subdirectory called 'resized'.

In one dimension only

• resize_all_x.m
• resize_all_y.m
• resize_all_z.m

In x and z dimensions simultaneously

• resize_all_xz.m

Usage

These functions require 2 (or 3) input arguments (in order):

1. output number
2. new resolution (for *xz.m input x resolution before z resolution)

Examples:

resize_all_x(5, 512);

will create a subdirectory called 'resized' which contains resized fields with an x-resolution containing 512 for all files for output number 5. A spins.conf file must be present.

resize_all_xz(5, 512, 256);

will create a subdirectory called 'resized' which contains resized fields with an x-resolution containing 512 and a z-resolution of 256 for all files for output number 5. A spins.conf file must be present.