自由汇流旋涡多相耦合输运演变机理

Mechanism of multiphase coupling transport evolution of free sink vortex

含自由液面的汇流旋涡抽吸演变中存在多相耦合、物质传输、能量剧烈交换等物理过程,其中所涉及的多相流体耦合输运机理是具有高度非线性特征的复杂动力学问题,多相黏滞耦合输运动力学建模与数值求解具有较高难度.针对上述问题,提出一种含自由液面的汇流旋涡多相耦合输运建模与求解方法.基于水平集-流体体积耦合(CLSVOF)计算方法,结合连续表面张力模型和可实现(k-ε)湍流模型,建立含自由液面的汇流旋涡多相耦合输运动力学模型;利用一种有效的体积修正方案来计算高速旋转多相流,保证流场质量守恒和无散度的速度场;结合相间耦合求解策略对多相流体分布与多相界面进行精确追踪.基于旋流场多特征物理变量,得到多相耦合界面动态演变与跨尺度涡团输运规律,揭示了多相耦合输运过程与压力脉动特性之间的相互作用机理.研究结果表明:多相耦合输运过程是流体介质过渡的关键状态,旋涡微团受到不同时空扰动模式在界面处形成层层螺纹波形;旋涡多相耦合输运过程随着水口尺度增大而增强,且耦合能量激波引起非线性压力脉动现象.研究结果可为旋涡输运机理、涡团跨尺度求解、流型追踪等方面的研究提供有益借鉴.

In the evolution of confluence sink vortex with a free surface,there exists some physical processes,such as multiphase coupling,mass transfer,and intensive energy exchange.Here,the transport mechanism of multiphase coupling is a complex dynamic problem with highly nonlinear characteristics.The mechanical modeling and numerical solution of multiphase viscous coupled transport are facing a significant challenge.To address the above problem,a method of modeling and solving multiphase coupling transport of the free sink vortex is proposed.Based on the coupled level set and volume-of-fluid(CLSVOF)method,a multiphase coupling transport model of the free sink vortex is set up with a continuous surface tension model and a realizable(k-ε)turbulence model.By using an effective volumetric correction scheme,the high-speed rotating flow is calculated,and the mass conservation of flow field and the velocity field without divergence are ensured.Then,an interphase coupling solution approach accurately traces the multiphase fluid distribution and multiphase interface.The multiphase coupling interface and cross-scale vortex cluster transport laws are obtained according to the multi-characteristic physical variables.The interaction mechanism between the multiphase coupling transport process and the pressure pulsation characteristics is revealed.The results show that the multiphase coupling transport is the critical state of the fluid medium transition.The vortex microclusters are subjected to different spatiotemporal disturbance modes and form the layered threaded waveforms at the interface.With the increase of the nozzle sizes,the multiphase coupling process is strengthened,and the coupling energy shock causes nonlinear pressure pulsation.This study can offer valuable references to the researches of the vortex transport mechanism,cross-scale solution of vortex cluster,and flow pattern tracking.