Numerical study of cavity natural convection flow with augmenting and counteracting effects by projection finite element method
Doctor of Philosophy
A numerical study of natural convection in cavities under the effects of thermocapillarity and gravity modulation is conducted in this research. Three different algorithms which are first-order explicit, second-order Taylor-Galerkin and semi-implicit schemes based on the projection finite element method (FEM) are developed. Each algorithm presents its own characteristics and advantages. By considering the problem characteristics and computational efficiency, the semi-implicit method is a better choice for this research. In this thesis, the physical investigation of cavity natural convection with augmenting or counteracting effects is divided into four parts. At first, the cavity flow with buoyancy force and thermocapillary effect is studied for different Marangoni numbers and aspect ratios. Next, the Benard convection with gravity modulation effects in normal gravity and zero-g gravity is investigated. The natural convection flow exhibits dramatically different flow structure under the influence of different modulation directions and frequencies. In addition, the natural convection with combined thermocapillarity and gravity modulation is explored for different modulation directions, frequencies and Marangoni numbers. Finally, the cavity natural convection flow with a deformable free surface is analyzed for different Grashof numbers and Marangoni numbers. Results of this research show that the surface tension provides a strong influence in the natural convection flow in both normal gravity and microgravity states. Particularly, the low aspect ratio and microgravity environments favor the development of thermocapillary-driven flow. On the other hand, the existence of gravity modulation makes the flow field different from the constant gravity state by applying different modulation directions and frequencies. The simultaneous presence of thermocapillarity and g-jitter creates a dramatically different flow pattern when compared to the results had without thermocapillary effect. When a deformable free surface is considered, the flow field and heat transfer rate at the corners of free surface are changed due to the deformation of free surface shape.
Applied mechanics; Mechanical engineering