Applicability of Kinematic and Diffusive models for mud-flows: a steady state analysis

• Published in: Journal of hydrology (Amsterdam) Vol. 559; pp. 585 - 595
• Main Authors: Di Cristo, Cristiana, Iervolino, Michele, Vacca, Andrea
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2018
• Subjects: Mud-flow; Power-law fluid; Simplified wave models; Steady flow; Power-law fluid; Simplified wave models; Mud-flow; Steady flow
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2018.02.016

•The paper studies the applicability of Kinematic-Diffusive models for mud-flows.•The fluid is represented with a power-law shear-thinning rheology.•Similarly to the clear-water studies, the steady state analysis is adopted.•The analytical solution of the flow depth profiles in a wide channel is derived.•Applicability criteria for clear-water are not conservative for shear-thinning fluids. The paper investigates the applicability of Kinematic and Diffusive Wave models for mud-flows with a power-law shear-thinning rheology. In analogy with a well-known approach for turbulent clear-water flows, the study compares the steady flow depth profiles predicted by approximated models with those of the Full Dynamic Wave one. For all the models and assuming an infinitely wide channel, the analytical solution of the flow depth profiles, in terms of hypergeometric functions, is derived. The accuracy of the approximated models is assessed by computing the average, along the channel length, of the errors, for several values of the Froude and kinematic wave numbers. Assuming the threshold value of the error equal to 5%, the applicability conditions of the two approximations have been individuated for several values of the power-law exponent, showing a crucial role of the rheology. The comparison with the clear-water results indicates that applicability criteria for clear-water flows do not apply to shear-thinning fluids, potentially leading to an incorrect use of approximated models if the rheology is not properly accounted for.