## Nek5000: Computational Fluid Dynamics Code

Nuclear reactor simulation: An elevation plot of the highest energy neutron flux distributions from an axial slice of a nuclear reactor core is shown superimposed over the same slice of the underlying geometry. This figure shows the rapid spatial variation in the high energy neutron distribution between within each plate along with the more slowly varying, global distribution. The figure is significant since UNIC allows researchers to capture both of these effects simultaneously.

Nek5000 is a computational fluid dynamics code that simulates unsteady incompressible fluid flow with thermal and passive scalar transport. It can handle general two- and three-dimensional domains described by isoparametric quad or hex elements. In addition, it can be used to compute axisymmetric flows. Nek5000 won a Gordon Bell prize for its outstanding scalability on high-performance parallel computers. It currently has more than 160 users and is a part of the CESAR co-design effort.