Numerical modelling of swirl flow induced by a three-lobed helical pipe

Increasingly in the process industries, the introduction of swirl flow upstream of bends is being used in particle-laden flow to reduce wear. This paper describes a computational fluid dynamics model of the swirl flow that is induced in an airflow passing through a horizontally mounted three-lobed helical pipe. It then goes on to discuss the results of the model verification and validation studies performed. The numerical model was used to further investigate the flows observed within and downstream of both a straight circular pipe and a three-lobed helical pipe that were previously studied during experiments conducted on a laboratory rig for a range of Reynolds numbers. A comparative analysis of the experimental and model predicted data concluded that the simulation results replicated well the experimental results for the control pipe. For the helical pipe, axial velocities were in reasonable agreement with experimental measurements across the range of Reynolds numbers studied. However, tangential velocities were under-predicted by an average of 35% in comparison to the experimental results. As a result, swirl intensity values were also under-predicted, but the values of the computed swirl decay rates were in agreement with those observed during the experiments.