减阻剂对管道内流动结构及安全性影响研究

减阻剂可以有效改变管道内流动结构，减少流动阻力，在保证管道输量的前提下，降低管道的工作压力，提高管道的安全性能。采用Giesekus模型对表面活性剂减阻流动进行直接数值模拟，并基于模拟计算结果，采用小波多分辨分析方法研究减阻剂对流动结构的影响，定量计算减阻剂的作用效果，分析其对管道运行安全的影响。计算结果表明:在减阻剂作用下，流向速度分量的大尺度脉动所含能量显著增强，与牛顿流体相比，减阻流体的大尺度结构增大约1.5倍，而小尺度流动结构明显减少，进一步证明了减阻剂对小尺度湍流结构的抑制作用。得到的减阻率为47.07%，可使管道在较低压力下运行，降低管道的安全风险，提升管道的安全性能。

Influence on flow structures and safety of pipeline by drag-reducing additives

The frictional resistance of fluid flow can be reduced observably by drag-reducing additives through changing the flow structure of pipeline, which can keep pipelines operating at lower pressure and much safer state in premise of same throughput. In this paper, the Giesekus model was adopted for direct numerical simulation of surfactant drag-reducing flow. Based on DNS data, wavelet analysis was employed to investigate the effect of drag-reducing additives to flow structure and pipeline safety, and the drag-reducing rate was calculated. The results showed that under the effect of drag-reducing additives, the energy contained in large scale fluctuation of streamwise velocity increases apparently, the large scale structure increases 1.5 times compared with the Newtonian fluid, meanwhile the small scale flow structure reduces significantly. It is further proved that drag reducing additives can extremely suppress small scale turbulence structure. The obtained drag reduction rate was 47.07%, which can make the pipeline running at lower pressure with much lower safety risk, so as to improve the safety performance of pipeline.