  This article discusses computational techniques for simulating natural
convection in three-dimensional domains using finite element methods with
tetrahedral elements. These techniques form a new numerical procedure for this
kind of problems. In this procedure, the treatment of advection by a wave
equation approach is extended to three-dimensional unstructured meshes with
tetrahedra.
  Numerical results of natural convection of an incompressible Newtonian fluid
in a cubical enclosure at Rayleigh numbers in the range $10^3$ to $10 ^6$ are
obtained and they are in good agreement with those in literature obtained by
other methods.
