论文标题
剪切流中运动学不稳定性的客观早期识别
Objective early identification of kinematic instabilities in shear flows
论文作者
论文摘要
提出了一种运动学方法，以鉴定流动不稳定性。通过在拉格朗日框架中定义流动不稳定，因为流体颗粒线的折叠增加，微妙的扰动及其不稳定的生长仅基于有限时间的材料线的曲率变化而早期检测到。材料线曲率是客观的，独立于参数化，并且可以应用于一般复杂性的流动，而无需了解基本流动。得出了欧拉速度模式的生长之间的分析连接，这些速度模式会扰动一般剪切流量和诱导的流量图和拉格朗日曲率变化。该方法经过验证，以迅速捕获不稳定的射流流动，在弯曲的机翼上的不稳定的分离剪切流以及在圆形圆柱体后面的尾流不稳定性时。
A kinematic approach for the identification of flow instabilities is proposed. By defining a flow instability in the Lagrangian frame as the increased folding of lines of fluid particles, subtle perturbations and unstable growth thereof are detected early based solely on the curvature change of material lines over finite time. The material line curvature is objective, parametrization independent, and can be applied to flows of general complexity without knowledge of the base flow. An analytic connection between the growth of Eulerian velocity modes perturbing a general shear flow and the induced flow map and Lagrangian curvature change is derived. The approach is verified to capture instabilities promptly in a temporally developing jet flow, an unstable separated shear flow over a cambered airfoil, and in the onset of a wake instability behind a circular cylinder.
