“经验关联法”耦合“多尺度特性”的表面活性剂湍流减阻机制及模型研究

The surfactant turbulent drag-reduction technology has great application potential in district heating/cooling system. However, the present drag-reduction data and theory obtained from experiments can be barely utilized to guide its practical application. It is mainly because that the understanding of drag-reduction mechanism is not clear enough and there is lack of drag-reduction model describing the relations between drag-reduction and flow conditions. Consequently, the drag-reduction of surfactant flow can’t be well predicted under different flow conditions. A new thought combining the empirical correlation method and multi-scale characteristic of surfactant flow is put forward in the present study to build the drag-reduction model in view of that the model can hardly be worked out only by experiments. The mesoscopic shear-induced behaviors of rodlike micelles will be studied to build the relationship between rodlike micelle length and flow conditions utilizing Brownian dynamic numerical simulation. The influences of different flow conditions on drag-reduction will be experimentally studied. Taking the rodlike micelle length that has high degree of relevance with drag-reduction as the empirical correlation parameter, the model describing the relations between drag-reduction and flow conditions can be established combining the results of numerical simulation and experiments. The drag-reduction model can be used to further explore and reveal the drag-reduction mechanism and predict the surfactant drag-reduction under different flow conditions. The present study provides new feasible idea for the research of drag-reduction model, and enriches the theory of surfactant turbulent drag-reduction, also provides theoretical support for promoting the application of surfactant drag-reduction technology.

表面活性剂湍流减阻技术在区域集中供热/供冷系统中应用潜力巨大，但现有减阻实验数据和理论很难指导其实际应用。主要原因在于对其减阻机制理解不够清晰，欠缺描述减阻性能与流动条件耦合关系的减阻模型，无法较好预测表面活性剂在不同流动条件下的减阻性能。纯实验法很难建立减阻模型，本课题提出“经验关联法”与“多尺度特性”相结合的研究新思路：利用介观布朗动力学数值模拟，研究介观尺度棒状胶束剪切诱导行为，建立描述各流动条件对棒状胶束长度影响规律的耦合关系式；通过实验研究获得不同流动条件对减阻性能的影响规律；取与减阻性能有高度关联性的棒状胶束长度作为经验关联参数，耦合数值模拟和实验结果，建立宏观尺度减阻性能与各流动条件间耦合关系的减阻模型，进一步探索和揭示减阻机制，准确预测不同流动条件下表面活性剂的减阻性能。该课题为减阻模型研究提供可行的新思路，进一步丰富表面活性剂减阻理论，为此技术推广应用提供理论支撑。

减阻机制不够清晰、减阻模型欠缺限制了表面活性剂湍流减阻技术的大规模实际应用。基于此，本项目利用介观布朗动力学数值模拟，研究了介观尺度表面活性剂棒状胶束剪切诱导行为，获得了各流动条件对棒状胶束剪切诱导行为的影响规律，建立了描述各流动条件对棒状胶束长度影响规律的耦合关系式；搭建了管道减阻实验平台，并实验获得了各流动条件对表面活性剂湍流减阻性能的影响规律；耦合数值模拟和实验结果，建立了宏观尺度表面活性剂减阻性能与各流动条件间耦合关系的减阻模型；在此基础上，将研究对象由单纯表面活性剂减阻体系扩展到聚合物/表面活性剂复配减阻体系，从介观分子动力学角度研究获得了复配体系内聚合物、表面活性剂分子之间的相互作用机制，并采用分子动力学模拟与实验测试相结合的方法证实此复配体系可用作消防减阻添加剂；此外，针对表面活性剂减阻剂在实际工业应用中失效的问题，分析工业应用中管道流体流动环境特点，研究了弱碱性溶液环境及铁锈对表面活性剂胶束结构及湍流减阻性能的影响，揭示了表面活性剂湍流减阻失效机制，提出了消除两种因素影响的方法。以上工作为推广表面活性剂湍流减阻技术的实际应用提供科学依据和理论基础。