Simulation of multiphase flow in venturi using comsol

A venturi tube is composed of three sections: a contraction section, a throat section, and a diffusion section. Its cross-section contracts first and then gradually expands. Flowing fluid through the throat section will be accelerated and pressure will drop as a result of the shrunken cross-section. It is known as a Venturi effect, which causes the fluid to be drawn into a vacuum.

In recent years, Venturi pipes have been widely used in flow measurement, natural gas transmission, internal combustion engine pressurization systems, and industrial waste gas cleaning and dust removal. In oil fields, oil is extracted from several wells and then accumulated in a manifold to be stored in a three-phase separator tank to extract the oil-dominated fluid by gravity. Multiphase flowmeters are used to measure the oil flow rate in each well in real time in order to maximize production capacity.

It is possible to explain and interpret these types of flows by classifying the distribution states of the interface between two gas and liquid phases, known as flow regimes or flow patterns. These flow regimes are generally affected by the shape and location of the pipeline, its flow direction, the physical properties of the phases and the flux of heat entering the pipe. V-Cone, orifice plate, Dall tube, and more frequently Venturi meters are the most widely DP flow meters used to determine the volumetric flow rate of multiphase flows. They use the principle that any restriction in the pipe will result in a change of pressure and causes a pressure drop across the restriction.

Table 1: Venturi meter advantages and disadvantages

The COMSOL software was used to simulate fluid flow in a venturi tube, and several factors were investigated to determine how mass flux and asymmetric flow are affected, such as the ratio of the throat section length to diameter, the diffusion angle, and the difference between inlet and outlet pressures.

According to the results, the lowest pressure point occurs between the contraction and throat sections of the venturi tube. With an increasing contraction ratio, vacuum degree rises, and mass flux increases. As the diffusion angle increases, both mass flux and vacuum degree decrease. Furthermore, a contraction ratio increase shortens a diffusion section of fully developed velocity.