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

Resumen

Method of Characteristics (MOC) needs to fulfil the Courant condition (C_n = 1.0) in order to guarantee the stability and convergence on the results. Otherwise, whenever C_n < 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 C_n 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 C_n > 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.