Improved Discrete Random Walk Stochastic Model for Simulating Particle Dispersion and Deposition in Inhomogeneous Turbulent Flows
Improved Discrete Random Walk Stochastic Model for Simulating Particle Dispersion and Deposition in Inhomogeneous Turbulent Flows
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DOI：
10.1115/1.4047538
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发表时间：
2020-10-01
影响因子：
2
通讯作者：
Ahmadi, Goodarz
中科院分区：
文献类型：
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作者：
Mofakham, Amir A.;Ahmadi, Goodarz
研究了不同版本的离散随机漫步模型在具有非均匀正态均方根速度波动和湍流时间尺度的湍流中的性能。采用OpenFOAMv2 - flow雷诺数紊流模型，对紊流通道中完全发育的顺流速度和壁面法向RMS速度波动曲线进行了评价。然后将结果应用于matlab粒子跟踪代码中，包括阻力和布朗力，并在单向耦合假设下评估随机注入直径为10nm至30 μ m的点粒子的轨迹。采用常规离散随机游动（DRW）模型、包含速度梯度漂移修正的改进DRW模型和包含速度和时间梯度漂移项的改进DRW模型，对流体示踪剂和有限粒径颗粒的分布和沉积速度进行了评估。结果表明，传统的drw模型会导致流点颗粒向壁面的过量迁移和错误的颗粒沉积速率。采用改进的drw模型得到的示踪粒子浓度分布仍然不均匀。结果表明，采用速度和时间尺度漂移修正后的改进drw模型可使液点颗粒分布均匀，使有限尺寸重颗粒的浓度分布合理。此外，改进的drw模型估计的不同粒径颗粒的沉积速度与现有数据吻合较好。
The performance of different versions of the discrete random walk models in turbulent flows with nonuniform normal root-mean-square (RMS) velocity fluctuations and turbulence time scales were carefully investigated. The OpenFOAMv2 - f low Reynolds number turbulence model was used for evaluating the fully developed streamwise velocity and the wall-normal RMS velocity fluctuations profiles in a turbulent channel flow. The results were then used in an in-house matlab particle tracking code, including the drag and Brownian forces, and the trajectories of randomly injected point-particles with diameters ranging from 10nm to 30 mu m were evaluated under the one-way coupling assumption. The distributions and deposition velocities of fluid-tracer and finite-size particles were evaluated using the conventional-discrete random walk (DRW) model, the modified-DRW model including the velocity gradient drift correction, and the new improved-DRW model including the velocity and time gradient drift terms. It was shown that the conventional-DRW model leads to superfluous migration of fluid-point particles toward the wall and erroneous particle deposition rate. The concentration profiles of tracer particles obtained by using the modified-DRW model still are not uniform. However, it was shown that the new improved-DRW model with the velocity and time scale drift corrections leads to uniform distributions for fluid-point particles and reasonable concentration profiles for finite-size heavy particles. In addition, good agreement was found between the estimated deposition velocities of different size particles by the new improved-DRW model with the available data.