Three-dimensional simulation of natural convection in a reservoir sidearm

Numerical simulations were conducted of turbulent natural convection in a shallow tetrahedron domain representing the sidearm of a lake or water reservoir. The tetrahedron cavity is a more realistic, three-dimensional approximation of a lake or reservoir sidearm than the two-dimensional triangle cavity often seen in the literature. Lateral temperature gradients exist due to the varying depth of the cavity, resulting in lateral circulation. These flows are important in a reservoir as they can carry with them particles and various pollutants, transporting and mixing them with the central section. Therefore, study in this area is important in water quality management. The simulations use a Cartesian grid with an Immersed Boundary Method for the sloped bottom surfaces. Heat input is through a solar radiation model consisting of a heat flux from the sloped bottom boundaries and an internal heating source term in the body of the water. Also studied is the night time model where cooling is through a heat flux at the top boundary. Scaling analysis from the literature is extended to suit the new geometry and numerical simulations are used to validate the results. The numerical simulations include calculating horizontal heat transfer profiles, volumetric flow rates, and analysis of complex flow features. The extension to three dimensions results in significant changes to the flow and introduces some complex features, such as helical flow both towards and away from the tip. Some general parameterisations are proposed for the tetrahedron cavity based on the numerical simulations. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792709]