Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Suppress Numerical Oscillations in Transient Mixed Flow Simulations with a Modified HLL Solver

Version 1 : Received: 21 February 2020 / Approved: 24 February 2020 / Online: 24 February 2020 (03:38:08 CET)

A peer-reviewed article of this Preprint also exists.

Mao, Z.; Guan, G.; Yang, Z. Suppress Numerical Oscillations in Transient Mixed Flow Simulations with a Modified HLL Solver. Water 2020, 12, 1245. Mao, Z.; Guan, G.; Yang, Z. Suppress Numerical Oscillations in Transient Mixed Flow Simulations with a Modified HLL Solver. Water 2020, 12, 1245.

Journal reference: Water 2020, 12, 1245
DOI: 10.3390/w12051245

Abstract

Transition between free-surface and pressurized flows is an crucial phenomenon in many hydraulic systems, including water distribution systems, urban drainage systems, etc. During the transition, the force exerted on the structures changes drastically, thus it is meaningful to simulate this process. However, severe numerical oscillations are widely observed behind filling-bores, causing unphysical pressure variations and even computation failure. In this paper, some oscillation-suppressing approaches are reviewed and evaluated on a benchmark model. Then a new oscillation-suppressing approach is proposed to admit numerical viscosity when the water surface is at proximity of conduct roof which has first order accuracy. This approach adds numerical viscosity when water surface is at the proximity of conduct roof. It can sufficiently suppress numerical oscillations under an acoustic wave speed of 1000m/s and is simple to apply. In comparison with two experiments, the simulation results of this method show good agreement and little numerical oscillations. The results in this paper can help readers to choose an appropriate oscillation-suppressing method to improve the robustness and accuracy of flow regime transition simulations.

Subject Areas

flow regime transition; finite volume methods; numerical oscillations; numerical viscosity; Preissmann slot model

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