Computational Fluid Dynamics Analysis of Flow in a Straight Flume for Sediment Erodibility Testing

Computational fluid dynamics calculations of flow in a straight flume for sediment erodibility testing were conducted. The calculations allowed improved postprocessing of the erosion data collected and better understanding of scour pit formation that is sometimes found in the flume’s test section. The flume is a $3\text{-}\mathrm{m}$ -long, rectangular ( $13\text{-}\mathrm{cm}$ -wide by $10\text{-}\mathrm{cm}$ -high) water conduit, which is placed on the sediment water interface during the sediment transport tests. The flume consists of a $1.6\text{-}\mathrm{m}$ inlet section, followed by a $1.1\text{-}\mathrm{m}$ test section, where the flowing water contacts the sediment. After erosion has occurred in the test section, the flow entering from the inlet section is an expanding flow. It generates a circulation cell and nonuniform bottom stress and pressure. Flow calculations were conducted for four different erosion depths (0, 1, 2, and $4\mathrm{cm}$ ) and for two different flow velocities (1 and $0.5\mathrm{m}∕\mathrm{s}$ ). After erosion had occurred, the effective stress in the test section was within 15% of the bottom stress calculated with the Schlichting equation, as long as the increased cross-sectional area was accounted for.