An Open Boundary Condition for Models of Thermals

Abstract

Numerical models of thermals usually introduce a closed box within which convection occurs. A boundary condition which allows inflow and outflow through the edges of the computational domain is discussed. The results of numerical experiments using this boundary condition are then compared and contrasted with those obtained when a rigid boundary is assumed. It is found that the flow development is especially sensitive to the choice of the upper boundary condition even before warm fluid reaches the top of the computational domain.