  This paper demonstrates the application of the density-based topology
optimisation approach for the design of heat sinks and micropumps based on
natural convection effects. The problems are modelled under the assumptions of
steady-state laminar flow using the incompressible Navier-Stokes equations
coupled to the convection-diffusion equation through the Boussinesq
approximation. In order to facilitate topology optimisation, the Brinkman
approach is taken to penalise velocities inside the solid domain and the
effective thermal conductivity is interpolated in order to accommodate
differences in thermal conductivity of the solid and fluid phases. The
governing equations are discretised using stabilised finite elements and
topology optimisation is performed for two different problems using discrete
adjoint sensitivity analysis. The study shows that topology optimisation is a
viable approach for designing heat sink geometries cooled by natural convection
and micropumps powered by natural convection.
