减阻水溶液槽道湍流特性POD分析

POD analysis for the turbulent characteristics of channel flow with drag-reducing aqueous solution

摘要:

为进一步分析减阻水溶液湍流减阻机理,对质量分数为30×10-6十六烷基三甲基氯化铵(CTAC)水溶液槽道湍流减阻流动进行了实验研究,并基于本征正交分解方法研究减阻水溶液流动中减阻剂对流动结构的影响．结果表明:CTAC水溶液流动在不同雷诺数(15×10⁴、25×10⁴和35×10⁴)下分别具有651％、700％和330％减阻效果;基于本征正交分解方法分析湍流脉动速度场,发现CTAC添加剂能够抑制湍流猝发过程中的低速流体的上喷及高速流体的下扫,即在一定程度上抑制了相干结构的发生及其发展过程,最终导致湍流减阻．

Abstract:

To investigate the turbulent drag-reducing mechanism of drag-reducing aqueous solution, turbulent drag reduction of 30×10-6 cetyltrimethyl ammonium chloride (CTAC) aqueous solution in a channel flow was investigated experimentally and the influence of the drag-reducing additives on the flow structures was studied based on proper orthogonal decomposition, and POD was used to analyze turbulent fluctuating velocity based on PIV. The experimental results showed that at different Reynolds numbers, such as, 15×10⁴, 25×10⁴ and 35×10⁴, drag reduction (DR) rate of CTAC aqueous solution can reach up to 651％, 700％ and 330％ respectively, and the CTAC additives can inhibit the ejection motion of low-speed fluid from the wall and sweep motion of high-speed fluid towards the wall associating with turbulent bursting events, that is to say, the CTAC additives can inhibit the formation and development of turbulent coherent structures, resulting in a great decrease of turbulent contribution to frictional drag and DR.