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A bypass transition model based on the intermittency function

机译:基于间歇函数的旁路过渡模型

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摘要

An intermittency model that is formulated in local variables is proposed for representing bypass transition in Reynolds-Averaged Navier-Stokes (RANS) computations. No external data correlation is used to fix transition. Transition is initiated by diffusion, and a source term carries it to completion. A sink term is created to predict the laminar region before transition and vanishes in the turbulent region. Both the source and sink are functions of a wall-distance Reynolds number and turbulence scales. A modification is introduced to predict transition in separated boundary layers. The transition model is incorporated with the k − ω RANS model. The model is validated with several test cases. Decent agreement with the available data is observed in a range of flows.An extended model for roughness-induced transition is proposed based on this intermittency model. To predict roughness effects in the fully turbulent boundary layer, published boundary conditions for k and ω are used. They depend on the equivalent sand grain roughness height, and account for the effective displacement of wall distance origin. Similarly in our approach, wall distance in the transition model for smooth surfaces is modified by an effective origin, which depends on equivalent sand grain roughness. Flat plate test cases are computed to show that the proposed model is able to predict transition onset in agreement with a data correlation of transition location versus roughness height, Reynolds number, and inlet turbulence intensity. Experimental data for turbine cascades are compared to the predicted results to validate the proposed model.
机译:提出了在局部变量中制定的间歇模型,用于表示雷诺平均Navier-Stokes(RANS)计算中的旁路过渡。没有使用外部数据关联来解决过渡问题。过渡是通过扩散开始的,源术语将其完成。创建一个下沉项以在过渡之前预测层流区域并在湍流区域中消失。源和汇都是壁距雷诺数和湍流尺度的函数。引入了修改以预测分离的边界层中的过渡。过渡模型与k-ωRANS模型结合在一起。该模型已通过多个测试案例进行了验证。在一定的流量范围内观察到了与现有数据的良好一致性。在此间歇模型的基础上,提出了一种扩展的粗糙度诱发转变模型。为了预测在完全湍流边界层中的粗糙度影响,使用已发布的k和ω边界条件。它们取决于等效的沙粒粗糙度高度,并说明壁距起点的有效位移。同样,在我们的方法中,光滑表面过渡模型中的壁距会根据等效砂粒粗糙度的有效起点进行修改。计算平板测试案例表明,所提出的模型能够与过渡位置与粗糙度高度,雷诺数和入口湍流强度的数据相关性相一致地预测过渡开始。将涡轮叶栅的实验数据与预测结果进行比较,以验证所提出的模型。

著录项

  • 作者

    Ge, Xuan;

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  • 年度 2015
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  • 原文格式 PDF
  • 正文语种 en
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