Numerical Study of Turbulent Pipe Flow Through Orifice Plate

The basic knowledge of fluid flow is crucial in every industry, dealing with oil, gas and chemicals.

In such industries, massive flow networks are necessary for continuous transportation of materials

and products among different units. This requires a deeper insight into flow through pipes

which are largely turbulent in nature. Frictional resistances, high pressure drops and reduced

discharge rates are associated with substantial energy loss in case of turbulent flow through pipes.

Flow through pipes is usually turbulent and therefore has complex flow structures with random

fluctuating components superimposing on the main flow. These movements of the local eddy

currents, generated by the internal roughness of the pipe, add a resistance to the flow. It is quite

difficult to predict the complex eddy motion and no turbulence model can completely analyze such

flows. Also, the study of the accuracy of orifice metering facilities is particularly of great

interest, since the uncertainty in measurement accuracy costs a lot in the natural gas industry every

year [12]. Although various types of orifices are present in the industry, circular orifice has

become the essential device while installing a pipe. Handful literature shows that much of the

investigation focuses on the calculation of discharge coefficients. In order to improve the metering

accuracy, it is necessary to improve the prediction techniques of flow and discharge coefficients.

1. Flow configuration

A flow in tube of 0.1m diameter with a circular orifice is employed in the present study. A

schematic configuration of the tube orifice is shown in Fig.1 below. Air enters the tube at a

pressure of 2bar and 20oC. This corresponds to the local acoustic velocity of 343m/s. Assuming the

Reynolds number (Re) 18000, which ensures the flow through this geometry is turbulent in nature.

The calculated velocity for this Re is 2.7m/s. Since the Mach number of the flow in this

configuration is much lower than 0.3, incompressibility assumption holds good. The inlet

turbulence intensity is 5% and length scale is 0.5D.