No abstract

-Orifices are widely used as flow restriction devices for the sake of pressure control, flowrate control or both. In these cases, the use of restricting orifices often result in high hydraulic losses, severe erosion in the presence of solid particles; cavitation in liquid flows, choking is gas flows in addition to noise and vibration. In this paper, the characteristics of flow through a multi-stage orifice plates fitted in a horizontal pipe of 25.4mm internal diameter has been investigated. Computational fluid dynamics calculations were performed using the realizable k-ε eddy viscosity model to predict the flow features. The effects of various parameters such as pipe flow velocity in the range 1−4m/s, orifice spacing of 1D and 2D, and orifice plate diameter ratios of 0.63 on axial velocity and pressure distributions were obtained. The location of vena contracta associated with the first orifice was found to be independent of addition of second orifice but varies with orifice diameter ratios while the presence of vena contracta downstream of the second orifice was found to depend on the orifice spacing. Not only the flow structure between the two orifices and downstream the second orifice was found to depend on the orifice spacing but also the total pressure drop and hydraulic losses. Orifice spacing of 1 and 2 pipe diameters gave the highest and lowest pressure recovery respectively compared to single orifice arrangement. The current study provides an insight into methods of pressure control without redesigning the complete flow system.