From 6210d3187e68d9911f2dfd0624a387f2ec7339e0 Mon Sep 17 00:00:00 2001 From: Paul Romano Date: Thu, 2 Aug 2012 17:26:27 -0400 Subject: [PATCH] Added description of universes and lattices. --- docs/source/methods/geometry.rst | 41 ++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/docs/source/methods/geometry.rst b/docs/source/methods/geometry.rst index 6f4755ce7..539e479b7 100644 --- a/docs/source/methods/geometry.rst +++ b/docs/source/methods/geometry.rst @@ -67,9 +67,47 @@ can be modeled in OpenMC. For example, the equation for a sphere centered at Universes --------- +OpenMC supports universe-based geometry similar to the likes of MCNP_ and +Serpent_. This capability enables user to model any identical repeated +structures once and then fill them in various spots in the geometry. A +prototypical example of a repeated structure would be a fuel pin within a fuel +assembly or a fuel assembly within a core. + +Each closed volume, or cell, in OpenMC can either be filled with a normal +material or with a universe. If the cell is filled with a univese, only the +region of the universe that is within the defined boundaries of the parent cell +will be present in the geometry. That is to say, even though a collection of +cells in a universe may extend to infinity, not all of the universe will be +"visible" in the geometry since it will be truncated by the boundaries of the +cell that contains it. + +When a cell is filled with a universe, it is possible to specify that the +universe filling the cell should be rotated and translated. This is done through +the ``rotation`` and ``translation`` attributes on a cell (note though that +these can only be specified on a cell that is filled with another universe, not +a material). + +It is not necessary to use or assign universes in a geometry if there are no +repeated structures. Any cell in the geometry that is not assigned to a +specified universe is automatically part of the "base" universe whose +coordinates are just the normal coordinates in Euclidean space. + Lattices -------- +Often times, repeated structures in a geometry occur in a regular pattern such +as a rectangular or hexagonal lattice. In such a case, it would be cumbersome +for a user to have to define the boundaries of each of the cells to be filled +with a universe. Thus, OpenMC provides a lattice capability similar to that used +in MCNP_ and Serpent_. + +The implementation of lattices is similar in principle to universes -- instead +of a cell being filled with a universe, the user can specify that it is filled +with a finite lattice. The lattice is then defined by a two-dimensional array of +universes that are to fill each position in the lattice. A good example of the +use of lattices and universes can be seen in the OpenMC model for the `Monte +Carlo Performance benchmark`_. + ------------------------------------------ Computing the Distance to Nearest Boundary ------------------------------------------ @@ -556,3 +594,6 @@ form of the solution: .. _constructive solid geometry: http://en.wikipedia.org/wiki/Constructive_solid_geometry .. _surfaces: http://en.wikipedia.org/wiki/Surface +.. _MCNP: http://mcnp.lanl.gov +.. _Serpent: http://montecarlo.vtt.fi +.. _Monte Carlo Performance benchmark: https://github.com/paulromano/benchmarks/tree/master/mc-performance/openmc