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Added supporting documentation

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Andrew Davis 2019-10-15 22:58:36 +01:00
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docs/source/io_formats/settings.rst
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@ -459,6 +459,15 @@ attributes/sub-elements:
*Default*: None
:library:
If this attribute is given, it indicates that the source is to be instanciated
from an externally compiled source function. This source can be as complex as
is required to define the source for your problem. The only requirement that
is made upon this source, is that there is a function called sample_source()
more documentation on how to build sources can be found in :ref:`custom_source`
*Deafult*: None
:space:
An element specifying the spatial distribution of source sites. This element
has the following attributes:
@ -591,6 +600,66 @@ attributes/sub-elements:
*Default*: false
.. _custom_source:
Custom Sources
++++++++++++++++++++++++++++++++++++
It is often the case that one may wish to simulate a complex source distribution,
which may include physics not present within OpenMC or to be phase space complex. It
is possible to define complex source with an externally defined source function
and loaded at runtime. A simple example source is shown below.
.. code-block:: c++
#include <iostream>
#include "openmc/random_lcg.h"
#include "openmc/source.h"
#include "openmc/particle.h"
// you must have external C linkage here
extern "C" openmc::Particle::Bank sample_source() {
openmc::Particle::Bank particle;
// wgt
particle.particle = openmc::Particle::Type::neutron;
particle.wgt = 1.0;
// position
double angle = 2.*M_PI*openmc::prn();
double radius = 3.0;
particle.r.x = radius*std::cos(angle);
particle.r.y = radius*std::sin(angle);
particle.r.z = 0.;
// angle
particle.u = {1.,0,0};
particle.E = 14.08e6;
particle.delayed_group = 0;
return particle;
}
The above source, creates 14.08 MeV neutrons, with an istropic direction
vector but distributed in a ring of radius three cm. This routine is
not particular complex, but should serve as an example upon which to build
more complicated sources.
.. note:: The function signature must be declared to be extern.
.. note:: You should only use the openmc::prn() random number generator
In order to build your external source you need the CMakeLists.txt file that
was created during the OpenMC installation process (found in the share subdirectory)
and your source file(s).
.. code-block:: bash
cp $HOME/openmc/share/CMakeLists.txt.
mkdir bld
cd bld
cmake .. -DSOURCE_FILES=source_sampling.cpp
make
You will now have a libsouce.so file in this directory, now point the library
attribute of source to this file and you will be able to sample particles.
.. _univariate:
Univariate Probability Distributions