MOC−BASED SECOND−ORDER EXPLICIT SCHEME FOR WATER HAMMER ANALYSIS

John Twyman Q

Resumen


Method of Characteristics (MOC) needs to fulfil the Courant condition (Cn = 1.0) in order to guarantee the stability and convergence on the results. Otherwise, whenever Cn < 1.0 is necessary to apply interpolation processes to calculate the state variables Q and H at the discretization nodes. In many cases, the application of MOC with first-order accuracy is more convenient due to its minor complexity, even if its principal disadvantage is the introduction of significant numerical attenuation as Cn value decreases away from 1.0, being necessary to have numerical schemes with higher accuracy in these cases. This paper introduces a MOC-based second-order explicit scheme useful to solve the transient flow when Courant is different from 1.0. It verifies that MOC 2nd-order is more accuracy than MOC 1st-order in a wide range of Courant numbers, even when Cn > 1.0, where with the help of numerical filters or artificial viscosities MOC can continue to function without to affect its accuracy or numerical stability. This feature allows get a greater time step which helps to reduce significantly the computation time.


Palabras clave


interpolation scheme, Method of Characteristics, numerical oscillations, order of interpolation, water hammer.

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DOI: http://dx.doi.org/10.22201/iingen.0718378xe.2018.11.1.56510