A.b. Kabiri Samani, M. Borgheie and M.h Saeidi,
Volume 24, Issue 2 (1-2006)
Abstract
The study of two-phase fluid flow behavior in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions and other similar conduits is of great importance. A two-phase mixture flowing in a pipe can exhibit several interfacial geometries such as bubbles, slugs or films, depending on the fluid and hydrodynamic properties of flow. The main variables, giving rise to a variety of flow patterns, include relative discharge rate of fluids and the pipe slope. The
flow patterns mostly attainable with air and water include stratified include and slug patterns. In this paper, the experimental results of pressurized water tunnel model are presented. The results include pressure transient and its variations for different hydraulic and geometric properties. It is shown that trapped and released air can cause tremendous pressure surges in the system and, eventually, may cause failure in systems (e.g. the maximum pressure inside the pipe would reach up to 10 times of upstream hydrostatic pressure). Finally, relations for forecasting maximum and minimum pressure in these situations are presented as a function of mean pressure, flow characteristics and pipe geometry.
M. Jamei, H. R. Ghafouri,
Volume 38, Issue 2 (2-2020)
Abstract
In this study, we present a numerical solution for the two-phase incompressible flow in the porous media under isothermal condition using a hybrid of the linear lower-order nonconforming finite element and the interior penalty discontinuous Galerkin (DG) method. This hybridization is developed for the first time in the two-phase modeling and considered as the main novelty of this research.The pressure equation and convection dominant saturation equation are discretized using the nonconforming Crouziex-Raviart finite element (CR FEM) and the weighed interior penalty discontinuous Galerkin (SWIP) method, respectively. Utilizing the nonconforming finite element method for solving the flow equation made the pressure and velocity values be consistent with respect to the degrees of freedom arrangement at the midpoint of the neighboring element edges. The boundary condition governing the simulation is the Robin type at entrance boundaries, and the time marching discretization for the governing equations is the sequential solution scheme. An H (div) projection using Raviart-Thomas element is implemented to improve the results’ resolution and preserve the continuity of the normal component of the velocity field. At the end of each time step, the non-physical oscillation is omitted using a slope limiter, namely, modified Chavent-Jaffre limiter, in each element. Also, in this study, the developed algorithm is verified using some benchmark problems and the test cases are considered to demonstrate the efficiency of the developed model in capturing the shock front at the interface of fluid phases and discontinuities.
