Prediction of the clogging profile using the apparent porosity and momentum impulse

This paper advances prediction of the clogging profile using the apparent porosity concept. The clogging profile is the vertical distribution of fine sand particles within a gravel-bed substrate that is overlain by hydraulically rough open channel flow. The author introduces the apparent porosity to represent the conveyance of fluid momentum through porous media, which is therefore a function of both the media and fluid, i.e., an apparent property. The author parameterizes the apparent porosity considering that coherent structures inject fluid momentum and sand into a clean gravel bed and the flow becomes laminar at its limit when the gravel is fully packed with sand. The author couples the apparent porosity with the previously published momentum-impulse model to provide a process-based prediction of the clogging profile, and the results show good agreement with experimental data. Results analyzed in dimensionless form via the dimensionless clogging depth show that the gravel porosity and roughness Reynolds numbers are the primary factors controlling clogging, which agrees with empirical research. In application, researchers can integrate the clogging profile model with sediment continuity models for gravel-bed rivers.