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在水击计算中,如果系统中流体的速度远小于波速,则用常规的特征线法来进行数值运算是十分有效的。当流体的粘性不很大时,采用一阶精度模型来处理摩擦项就足够了。但是在粘性摩擦起较大作用的问题中,利用一阶精度模型可能会引起解的不稳定,或给出错误的结果,为了在不使用较小的距离步长的条件下,保证解的稳定性和改进解的精度,有必要使用高阶精度模型来处理摩擦项。
In the calculation of water hammer, if the velocity of the fluid in the system is far less than the wave velocity, it is very effective to perform the numerical calculation by the conventional characteristic line method. When the fluid viscosity is not very large, the first-order accuracy model to deal with the friction term is sufficient. However, in the problem that the viscous friction plays a major role, using the first-order accuracy model may lead to instability of the solution or give wrong results. In order to ensure the stability of the solution without using smaller distance steps And improve the accuracy of solution, it is necessary to use the high-order precision model to deal with the friction term.