Multiphase flow

In fluid mechanics, multiphase flow is the simultaneous flow of materials with two or more thermodynamic phases. Virtually all processing technologies from cavitating pumps and turbines to paper-making and the construction of plastics involve some form of multiphase flow. It is also prevalent in many natural phenomena.Where G = mass flow rate, g = gas, l = liquid and s = solid.The Volumetric flow rate, defined as the volume of fluid passing through a cross sectional area per unit of time: In fluid mechanics, multiphase flow is the simultaneous flow of materials with two or more thermodynamic phases. Virtually all processing technologies from cavitating pumps and turbines to paper-making and the construction of plastics involve some form of multiphase flow. It is also prevalent in many natural phenomena. These phases may consist of one chemical component (e.g. flow of water and water vapour), or several different chemical components (e.g. flow of oil and water). A phase is classified as continuous if it occupies a continually connected region of space. Whereas a classification of disperse is applied when the phase occupies disconnected regions of space. The continuous phase may be either gaseous or a liquid. The disperse phase can consist of either a solid, liquid or gas. Two general topologies can be identified, disperse flows and separated flows.The former being those consisting of finite particles, drops or bubbles distributed within a continuous phase. The latter is defined as consisting of two or more continuous streams of fluids separated by interfaces. The study of multiphase flow is strongly linked to the development of fluid mechanics and thermodynamics. A key early discovery was made by Archimedes of Syracuse (250BCE) who postulated the laws of buoyancy, which became known as the Archimedes' Principle - which is used in modelling multiphase flow. In the mid 20th century, advances in nucleate boiling were developed and the first two-phase pressure drop models were formed primarily for the chemical and process industries. In particular Lockhart and Martinelli (1949) presented a model for frictional pressure drop in horizontal, separated two-phase flow, introducing a parameter that is still utilised today. Between 1950 and 1960, intensive work in the aerospace and nuclear sectors triggered further studies into two-phase flow. In 1958 one of the earliest systematic studies of two-phase flow was undertaken by Soviet scientist Teletov. Baker (1965) conducted studies into vertical flow regimes. From the 1970's onwards, multiphase flow especially in the context of the oil industry has been studied extensively due to the increasing dependence of petroleum by the world economy. The 1980s saw further modelling of multiphase flow by modelling flow patterns to different pipe inclinations and diameters and different pressures and flows. Advancements in computing power in the 1990's allowed for increasingly complex modelling techniques to modelling multiphase flow, flows that were previously limited to one-dimensional problems could be pushed to three-dimensional models. Projects to develop multiphase flow metering technology (MFM), used to measure the rate of individual phase flow appeared in the 1990s. The impetus behind this technology was a forecasted decline of production from the major North Sea oil fields. Oil companies that created early prototypes included BP and Texaco, MFMS have now become ubiquitous and are now the primary metering solution for new-field developments.