Transient Slurry Flow Phenomena after Bends in the Vertical Plane
An experimental study and analysis into the origin and development of density waves within pipeline systems using a sedimentation and erosion unbalance model
T. van der Voort (TU Delft - Civil Engineering & Geosciences)
Cees van Rhee – Graduation committee member (TU Delft - Offshore and Dredging Engineering)
A.M. Talmon – Graduation committee member (TU Delft - Offshore and Dredging Engineering)
E. de Hoog – Mentor (TU Delft - Offshore and Dredging Engineering)
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Abstract
Density waves inhibit the stability of (long) pipelines, which cannot be predicted using current day design tools. Density waves are formed due to an inverse relationship between sand eroding and settling in a pipeline. By designing and building a dedicated flow loop, an experimental study on how the erosion and sedimentation of sand in a pipe is influenced by particle size and concentration is conducted. Moreover, it is determined whether the erosion and sedimentation process can be modeled numerically using existing analytical pick-up functions. This could be applied for predicting density waves in horizontal pipelines.
From the experimental study it is found that at higher concentrations, the caterpillar-like movements of the bed, associated with the sedimentation and erosion unbalance at high concentrations, were observed more and more frequently. The influence of the mean grain size diameter can be characterised as the ability of the mixture to trigger amplifying density waves in the horizontal measurement section. Only the coarser sands used in the experiments were found to experience the sliding-stopping behaviour. Implementing different analytical pick-up functions to simulate the experimental study resulted in sufficiently accurate results. Depending on the pick-up function on how much calibration was required the measurements could be simulated adequately.