Density Wave Amplification During Hydraulic Transport: The Effect of Pipeline Design Parameters

Pipelines with combined vertical and horizontal pipes can be subject to transient redistribution and accumulation of sediment, also referred to as transient density wave amplification. This process is important to understand for dredging and especially for deep sea mining applications, where a horizontally oriented jumper hose is connected to a long vertical riser. Transient accumulation could ultimately lead to pipeline blockages or pump drive failures. Density wave amplification is partly caused by a velocity difference of particles between horizontal and vertical pipes, and partly by system wide interaction between density waves and the centrifugal pump. Density wave amplification was witnessed at mixture velocities far exceeding the deposit limit velocity (de Hoog et al. 2022), and as such the stability of the pipeline cannot be predicted by designing a pipeline operating point with conventional steady-state design methods. Specifically, the conventional steady-state design methodology only considers steady-state resistance and pump curves to obtain an operating point, and aims to design the operating point above the deposit limit velocity. Transient modeling using 1D Computational Fluid Dynamics (CFD) has shown to be able to predict density wave amplification. In this article the 1D Driftflux model developed by de Hoog et al. (2022) is applied to investigate the influence of system parameters on the rate of density wave amplification. In the simulations the following system parameters are varied: pump drive characteristics, the diameter of the horizontal pipes and the application of flow feedback control.