: Nowadays there are multiphase flows in different industries and it is important to investigate these flows. So far many people have researched on these flows and investigated from different aspects. The most important challenge for investigation of these flows is presentation of a suitable model for them. The multiphase flow inside the pipelines has different forms that are called flow regimes. In fact, flow regimes are different states of flow that different phases in a multiphase flow have relative to each other. Since the flow regimes are effective in pipeline design, a lot of researches have been done for flow regimes prediction. Stratified and Slug flows are samples of flow regimes. The slug flow exerts additional stresses on pipelines. It is desirable to prevent this regime in the pipelines. One of the equipments that is used for this application is slug catcher. The slug catchers have various types. Finger-type slug catchers are usually used in downstream of pipeline or entrance of gas refineries. The flow regime in slug catcher is stratified to prevent slugs’ flows enter refinery. In slug catchers flow is splited into different phases to improve performance of downstream equipments. In this thesis different types of flow regimes are investigated and map of flow regimes are shown. Also different types of slug catchers and splitting mechanisms in them are discussed. Thereafter equations for stratified and slug regimes are given. Types of stratified regimes with flat, curved and wavy interfaces and their equations are investigated. Thereafter different kinds of turbulence models are used. At the end, flow in a slug catcher is simulated with ANSYS CFX and influence of fingers slope, flow rate and adding reducers at entrance of fingers, on flow in slug catcher are investigated. The results indicated that increasing the pressure at a given flow rate leads to decreasing the flow level in slug catcher fingers. Diagram of inlet volume flow rate related to different finger slopes are drawn and compared with same diagram for St. Fergus and Den Helder slug catchers. According to this diagram optimum slope for South Pars slug catchers is about 1.5%. In this thesis also effect of inlet gas and liquid superficial velocity on flow distribution in fingers and inlet volume of liquids into the gas risers investigated. The results showed that in general increasing the amount of liquid superficial velocity at a fixed gas superficial velocity decreases gas inlet to the risers and increasing the gas superficial velocity at a fixed liquid superficial velocity will increase inlet of liquid to gas risers. The results showed that if the expander inserted instead of equal size pipe, distribution of mass flow in the fingers will be improved. In this case mass flow distribution in fingers with 44”*48” expander is better than 42”*48” and 40”*48” expanders. The results showed that with increasing the size of expanders from 40”*48” to 44”*48” inlet momentum of liquid and gas and volume of liquids in fingers will be decreased. Also in this thesis showed that best turbulence model to simulate the flow in slug catcher is SST. Keywords: Multiphase flow, Stratified flow, Slug flow, Turbulence Models, Finger-Type Slug Catcher