This paper investigates the spatial evolution of a disturbance in an open-channel flow of a power-law fluid at non-uniform accelerated and decelerated initial profiles, up to the occurrence of roll-waves in mild and steep slope channels. Both theoretical and numerical analyses are applied to the depthaveraged continuity and momentum conservation equations, deduced from the von Kármán’s integral method. For the theoretical investigation, the nonlinear near-front expansion technique was applied. Then, the full nonlinear problem in its conservative formulation was numerically solved. Independently of the rheology of the flowing medium, non-uniform initial conditions strongly influence the perturbation celerity, the disturbance evolution and the roll-wave development. For mild slope channels, an initially decelerated profile of shear-thinning fluids has a stabilizing effect, while the opposite is found for accelerated profiles. For shear-thickening fluids, only the stabilizing effect caused by a decelerated profile is observed. In steep slope channels, independently of the fluid rheology, decelerated initial conditions promote roll-wave occurrence, while accelerated conditions inhibit the perturbation growth. Although experimental verifications are needed, the present results have to be properly accounted for in defining roll-wave prediction methods and in assigning appropriate boundary conditions to enhance or to reduce their formation.

Development of roll-waves in power-law fluids with non-uniform initial conditions / Campomaggiore, Francesca; DI CRISTO, Cristiana; Iervolino, Michele; Vacca, Andrea. - In: JOURNAL OF HYDRAULIC RESEARCH. - ISSN 0022-1686. - 54:3(2016), pp. 289-306. [10.1080/00221686.2016.1140684]

Development of roll-waves in power-law fluids with non-uniform initial conditions

Di Cristo Cristiana;Vacca Andrea
2016

Abstract

This paper investigates the spatial evolution of a disturbance in an open-channel flow of a power-law fluid at non-uniform accelerated and decelerated initial profiles, up to the occurrence of roll-waves in mild and steep slope channels. Both theoretical and numerical analyses are applied to the depthaveraged continuity and momentum conservation equations, deduced from the von Kármán’s integral method. For the theoretical investigation, the nonlinear near-front expansion technique was applied. Then, the full nonlinear problem in its conservative formulation was numerically solved. Independently of the rheology of the flowing medium, non-uniform initial conditions strongly influence the perturbation celerity, the disturbance evolution and the roll-wave development. For mild slope channels, an initially decelerated profile of shear-thinning fluids has a stabilizing effect, while the opposite is found for accelerated profiles. For shear-thickening fluids, only the stabilizing effect caused by a decelerated profile is observed. In steep slope channels, independently of the fluid rheology, decelerated initial conditions promote roll-wave occurrence, while accelerated conditions inhibit the perturbation growth. Although experimental verifications are needed, the present results have to be properly accounted for in defining roll-wave prediction methods and in assigning appropriate boundary conditions to enhance or to reduce their formation.
2016
Development of roll-waves in power-law fluids with non-uniform initial conditions / Campomaggiore, Francesca; DI CRISTO, Cristiana; Iervolino, Michele; Vacca, Andrea. - In: JOURNAL OF HYDRAULIC RESEARCH. - ISSN 0022-1686. - 54:3(2016), pp. 289-306. [10.1080/00221686.2016.1140684]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/700998
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