# Rotating Translating STL Bunny

From Serpent Wiki

This example demonstrates the use of time-dependent transformations in the context of STL-objects. Time dependent transformations are also applicable to other Serpent objects.

## Input

**The main input file:**

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Geometry and material information % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Box containing bunny: surf 1 cyl 0.0 0.0 17.0 -0.1 27 cell 1 0 fill 1 -1 % Fill box with mesh based universe cell 2 0 outside 1 % Outside of the box is outside % --- Create the background universe (filled with void) surf 3 inf cell 4 2 void -3 % --- Create the STL-bunny solid 2 1 2 % type, universe, bacground universe 10 4 5 4 3 2 % search mesh split, depth and sizes 1 1E-5 % ray test, merge radius body fuel fuel fuel % solid name, cell name, material name file fuel "bunny.stl" 1.00 0 0 0 % body name, file, scaling factor, origin % --- Composition for bunny: mat fuel 4.7984E-02 rgb 222 222 222 92235.03c 4.4994E-02 92238.03c 2.4984E-03 92234.03c 4.9184E-04 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Add up and down translations using acceleration % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Upwards acceleration of 1e13 cm/s^2 from 0.0 s to 0.9e-6 s transa u 1 tlim 0 0.9e-6 3 0 0 1e13 % --- Downwards acceleration of 1e13 cm/s^2 from 0.9e-6 s to 2.7e-6 s % First for slowing down and then for acceleration. transa u 1 tlim 0.9e-6 2.7e-6 3 0 0 -1e13 % --- Upwards acceleration of 1e13 cm/s^2 from 2.7e-6 s to 3.6e-6 s % For slowing down transa u 1 tlim 2.7e-6 3.6e-6 3 0 0 1e13 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Add rotations using acceleration % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Angular acceleration to the negative mathematical direction % around axis defined by vector starting from 0.0 0.0 0.0 with i, j, k % components 0.0 0.0 1.0. Magnitude of angular acceleration is % 1.11111111111111e+14 degrees/s^2 from 0.0 s to 1.8e-6 s % (results in rotation of 180 degrees in 1.8 e-6 s) % NOTE: The signs are inverted for Serpent 2.1.29 (positive sign corresponds to % negative rotation) transa u 1 tlim 0 1.8e-6 3 rot 0.0 0.0 0.0 0.0 0.0 1.0 1.11111111111111e+14 % --- Angular acceleration to the positive mathematical direction % around axis defined by vector starting from 0.0 0.0 0.0 with i, j, k % components 0.0 0.0 1.0. Magnitude of angular acceleration is % 1.11111111111111e+14 degrees/s^2 from 1.8e-6 s to 3.6e-6 s transa u 1 tlim 1.8e-6 3.6e-6 3 rot 0.0 0.0 0.0 0.0 0.0 1.0 -1.11111111111111e+14 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Run & plot parameters: % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % --- Link cross section libraries set acelib "/home/vvvillehe/XSdata/xsdir0K" % --- Link dynamic source (this way the geometry will be plotted for each time interval) set dynsrc "./source" 1 % --- Define time-interval structure to be used with the simulation % 180 equally wide time-intervals between 0 s and 3.6e-6 s tme simutime 2 180 0.0 3.6e-6 % --- Simulate a small number of neutrons just to get the plots set nps 5000 10 simutime % --- Increase the precursor and neutron buffer sizes for the dynamic simulation set pbuf 40 set nbuf 40 % --- Create plots for each plot plane plot 1 500 399 plot 2 500 399 plot 3 500 500

**Additional input-files:**

- bunny.stl
- The dynamic source files (source.*) need to be created using a separate criticality source simulation.

## Running

**NOTE:** Since the delayed neutron precursors are not rotated and/or translated alongside with the geometry, some of them will fall outside of the bunny during some parts of the simulation and be emitted from the void-part of the geometry instead. This will lead to a number of warning messages such as

***** Tue Jun 20 14:58:13 2017 (seed = 1497959831) Warning message from function SamplePointDelnu: Precursor is not in material? x = -2.443193E+00, y = -4.201429E+00, z = 9.463751E+00 Cell name 4

## Output

The following animation can be compiled from the 180 plots rendered for each of the three plotting planes:

## Notes

- The transformations are updated at time-interval boundaries, which means that the geometry is static for each time-interval.
- The positions of neutrons and precursors are not updated as the transformations are updated.
- In external source simulations (no delayed neutrons, no coupled calculation) the geometry plots are only produced for the first time interval, although the transformations are applied similarly.