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Table of Contents

## Name

snapdisk - assign rotation to a disk

## Synopsis

snapdisk [parameter=value]

## Description

snapdisk assigns rotation in the XY-plane to an assumes disk where forces have been assigned by another program (e.g. hackforce). The rotational velocities are computed from the two-dimensional forces and radii as follows:
```      v = sqrt(a.r)
```
One can optionally also supply a known rotation curve,in tabular format, to assign rotational velocities.

## Parameters

The following parameters are recognized in any order if the keyword is also given:
in=
input file (snapshot) [???]
out=
output filename [???]
omega=
rotation (counterclock) [0.0]
rotcur=
Optional rotation/outflow curve (table: r,v) []
sign=
Sign of rotcur [1]
outflow=
Outflow or Rotation/Spin ** not implemented **[f]
times=
times of snapshots to copy [all]

## Examples

Here is an example of computing the rotation curve of a test disk that could live inside a Kuijken-Dubinsky Disk-Bulge-Halo composite model. After using hackforce(1NEMO) to compute the forces due to the KD95 model, snapdisk will compute the matching rotational velocities to be in circular motion.
```% mkkd95 a0
% mkdisk test1 10000 rmin=0.0001 rmax=8 mass=0.00001
% hackforce a0 test2 test1
% snapdisk test2 test3
% snapprint test3 r,vt > test3.rotcur
% tabplot test3.rotcur  1 2 0 8 0 1.6  xbin=0:10:0.1 tab=t > test3a.rotcur
% tabplot test3a.rotcur 1 2 0 8 0 1.6  line=1,1 point=2,0.1
```

## Bugs

some options in this program are not functioning correctly yet, as it was quickly cloned off snapspin

## See Also

snaprotate(1NEMO) , snapspin(1NEMO)

Peter Teuben

## Update History

```03-Aug-06    V1.0 Created at GH2006    PJT
```