液体管道高频水力瞬变过程的数值模拟

Numerical simulation for high-frequent transients in liquid pipe flow

目前在液体管道高频水力瞬变分析中,人们通常采用经典的拟稳态摩阻模型进行分析。但这种方法针对管壁切应力具有拟稳态特性的缓慢瞬变的分析是可行的,而对高频瞬变流动过程而言却不能准确预测水击压力波具体的衰减过程以及出现的波形畸变现象。介绍了一种新的考虑瞬时加速度对高频水力瞬变过程影响的非恒定摩阻模型,并结合特征线法给出了其数值解法,最后通过实例验证了该模型能比经典的拟恒定摩阻模型更为准确地模拟液体管道中高频瞬变流压力波的衰减和波形畸变。该模型对计算机的要求和计算耗时与经典的拟稳态摩阻模型相差不大,是一种具有良好工程应用潜力的液体管道高频瞬变分析数学模型。

Traditionally the hydraulic transient analysis in liquid pipe flow is based on the classic quasi-steady assumption that the unsteady friction in transients can be approximately calculated by the formulas used in steady pipe flow,i.e.quasi-steady friction model.The model,in fact,is only applicable to slow transients in liquid pipe flow.And it is not applicable to rapid transients because it would lead to significant discrepancies in attenuation and phase shift of pressure traces compared to the results of measurements.In this paper,a new unsteady friction model which is based on both local temporal and convective derivatives of velocity is proposed and its numerical solution with the method of characteristics is obtained.The corresponding calculation programs of the traditional quasi-steady friction model and the unsteady friction model have been developed and applied to transient simulation in an experimental pipeline.Compared to the results of measurements,the unsteady friction model show more accurate and predominant in simulating high-frequent transients in liquid pipe flow.