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Lattice Boltzmann approach for immiscible multiphase flow.

机译：不混溶的多相流的莱迪思·波尔兹曼方法。

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摘要

Immiscible multiphase flows are encountered in many engineering applications. However, due to the complicated interfacial topologies and complex flow dynamics, the basic understanding of the immiscible multiphase flow is still missing and efficient numerical methods are lacking. This dissertation presents a systematic effort to develop a lattice Boltzmann multiphase numerical method. Our focus is on the mixing and transport across fluid interfaces in immiscible multiphase flows.; Unlike traditional methods solving the macroscopic continuum Navier-Stokes equations, the lattice Boltzmann method (LBM) solves the same macroscopic physics, but based on microscopic models and mesoscopic kinetic equations, i.e. the Boltzmann equation. By incorporating molecular interactions, phase separation and interfacial dynamics can be properly modeled. To control numerical errors, we introduce two sets of distribution functions, the index distribution function g for tracking the density interfaces, and the pressure distribution function g for tracking the flow hydrodynamics. A series of benchmark studies of the resulting LBM multiphase model, including the Laplace Law, dispersion of capillary wave, bubble relaxation and linear growth of the Rayleigh-Taylor instability, have been conducted.; We have carried out simulations for both the two- and three-dimensional Rayleigh-Taylor (R-T) instabilities using the LBM multiphase model. Most of the known features of the R-T instabilities were reproduced. In addition, we found several new physical insights, including a reacceleration of spikes at late stages, the dependence of bubbles and spikes on fluid viscosity, complicated flow structure patterns and effects of surface tension on interface pinching. A parametric study were conducted on the evolutions of bubbles and spikes.; Numerical studies of the two-dimensional two-phase Kelvin-Helmholtz instability have been undertaken to investigate effects of surface tension. We observed that large-scale vortex core could be broken up by surface tensions. Small-scale vortices are generated near the interfaces. Several types of interface pinch-off occur and droplets are formed.; Finally we examined the energy spectrum of two-dimensional immiscible two-phase forced homogeneous turbulence. A new k--2 scaling behavior in the inertial sub-range was found. A tentative explanation based on an analogy with Burgers turbulence was given.
机译：在许多工程应用中会遇到不混溶的多相流。但是，由于复杂的界面拓扑和复杂的流动动力学，仍然缺少对不混溶多相流的基本了解，并且缺乏有效的数值方法。本文为系统发展格子Boltzmann多相数值方法提供了系统的努力。我们的重点是在不混溶的多相流中跨流体界面混合和传输。与解决宏观连续体Navier-Stokes方程的传统方法不同，晶格Boltzmann方法（LBM）解决了相同的宏观物理学问题，但基于微观模型和介观动力学方程，即Boltzmann方程。通过结合分子相互作用，可以正确地模拟相分离和界面动力学。为了控制数值误差，我们引入了两组分布函数，用于跟踪密度界面的指数分布函数g和用于跟踪流动流体动力学的压力分布函数g。已对所得的LBM多相模型进行了一系列基准研究，包括拉普拉斯定律，毛细管波分散，气泡弛豫和瑞利-泰勒不稳定性的线性增长。我们使用LBM多相模型对二维和三维Rayleigh-Taylor（R-T）不稳定性进行了仿真。再现了R-T不稳定性的大多数已知特征。此外，我们发现了一些新的物理见解，包括后期尖峰的重新加速，气泡和尖峰对流体粘度的依赖性，复杂的流动结构模式以及表面张力对界面收缩的影响。对气泡和尖峰的演变进行了参数研究。为了研究表面张力的影响，已经进行了二维两相Kelvin-Helmholtz不稳定性的数值研究。我们观察到，大型涡流芯可能会因表面张力而破裂。在界面附近会产生小规模的涡旋。发生几种类型的界面夹断并形成液滴。最后，我们研究了二维不混溶的两相强迫均匀湍流的能谱。在惯性子范围内发现了新的k--2缩放行为。根据伯格斯湍流的类比给出了一个初步的解释。

著录项

  • 作者

    Zhang, Raoyang.;

  • 作者单位

    University of Delaware.;

  • 授予单位 University of Delaware.;
  • 学科 Engineering Mechanical.; Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 211 p.
  • 总页数 211
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;等离子体物理学;
  • 关键词

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