Characterisation of flow conditions for contact erosion analysis using PIV

The aim of this paper is to examine the flow characteristics at the initiation of contact erosion.
When water flows through fine soil to a coarser soil layer, changes of the flow properties may occur due to
transition of the pore structure. A pore scale experiment was developed in order to explore the local flow behaviour
which leads to migration of fine particles into a coarse structure. Optical access to the pore structure
was obtained by having a transparent soil model consisting of hydrogel beads. This allowed water to be used as
the fluid phase and resulted in a more adaptable Particle Image Velocimetry (PIV) system. Upward seeded flow
was applied to the test section and illuminated using a low risk Light Emitting Diode (LED) light sheet. After
calibrating the set-up with macroscopic flow rate measured by flow meter, images of the contact zone of coarse
and fine particles were taken with different flow boundary conditions using a high speed camera. Qualitative and
quantitative analysis were carried out to identify spatial variability of the flow conditions which led to initiation
of the fine particle movement. Results show that the local reorientation of the flow will lead to local initiation
of the contact erosion. Major reasons for this behaviour are discussed in this paper.