Transient of flow restart in a gas void embedded gelled pipeline and voids deformation

The multiphase flow of complex fluids has a wide range of applications due to its influence on modification in the physical properties of the medium. Some examples are waxy gel, aerated concrete, and food products, which present a complex fluid-gas interface during processing and pipeline transportation. For instance, the pressure applied to dislodge the waxy gel structure confronts the high compressibility of the gas voids. The interaction of the pressure front with gas voids leads to localized deformation, causing extensive structural evolution of the gelled medium. Such interaction during initial pressure propagation significantly impairs the crystal network. An understanding of the pressure propagation mechanism is imperative to demonstrate the role of void space during the transient of a start-up operation. The simulation results for the pressure profile indicate a considerable delay in its propagation owing to the difference in compressibility of the two phases. Further propagation of pressure depends on compressive deformation of the gas void as a result of degraded upstream gel movement. A detailed examination of the 2-D circular gas void's motion and corresponding topological changes illustrates the localized gel degradation in the vicinity of the gel-gas interface.