Analysis of thermal effects on sediment grain escape velocity under combined cohesive and viscous forces using the truncated pyramid model

Abstract

A sediment grain on a riverside is surrounded by similar grains and is subjected to both cohesive and viscous forces. The present study considers the orientation of sediment grains based on the established truncated pyramid model and proposes an expression for the grain’s escape velocity. The escape velocity depends strongly on the inter-grain separation gap and temperature for a given water volume entrapped between two neighboring grains. This serves as a key measure of the volumetric erosion rate. A thorough comparative study was conducted, linking the escape velocity values reported in published work—where only cohesive forces were considered—with results obtained when both viscous and cohesive forces were accounted for under varying thermal conditions. Both scenarios were evaluated at a fixed liquid bridge volume and at different separation gaps, while all other parameters were kept constant. The findings revealed that the escape velocity increased relative to that reported in earlier research. In this study, the combined effect of viscous and cohesive forces results in a significant increase in the escape velocity required for a grain, indicating enhanced stability of the riverside compared to cases where only cohesive forces are considered at lower separation times. For the 1st time, temperature dependency is incorporated in the truncated pyramid model. In addition, a one-second threshold was identified, after which viscous forces and temperature no longer significantly affect grain binding.

Keywords

Separation gap / Sediment grain / Cohesive force / Escape velocity / Viscous force / Temperature

Funding

None.

Conflict of interest

The authors declare that they have no competing interests.

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