The Interaction between a Spatially Oscillating Jet and a Crossflow

横流中的射流是一种基本的流动情况，它可以在几种应用中找到，如燃烧室中的燃料混合、涡轮机叶片的薄膜冷却或机翼上的主动流动控制。关于这一主题的长期研究历史提供了对注入横流的定常射流的基本流场的全面了解。最近，一些研究已经检查了空间振荡射流振荡器在横流中发出的流体。射流振荡不需要任何移动部件，并且仅基于内部流体动力学，这是这些装置的主要优点之一。近年来，空间振荡射流在横流中的有效和高效应用已被证明是增强混合和主动流动控制的重要手段。然而，尽管从基本的流动可视化提出了一些建议，空间振荡射流的上级性能的驱动机制仍然是未知的。然而，这些信息对于基本理解和应用程序的适当优化过程至关重要。该流场的三维性和不稳定性以及高振荡频率和速度使得实验和数值研究具有挑战性。在所提出的工作中，实验研究的基本，不可压缩流场的空间振荡射流与横流的相互作用。射流由安装在风洞内的射流振荡器发出。流动可视化用于提供对流场的初步定性洞察。一个可遍历的立体粒子图像测速系统与建立相平均技术相结合，产生的三维，时间分辨流场。定量数据（例如，轨迹，涡量，和流动特征）进行了比较，从文献中的稳定射流横流。这种比较有望揭示流场之间的共性和差异，阐明上级性能的驱动机制，并可能找到新的应用。这个问题的复杂性需要缩小调查的参数。在所提出的工作中，速度比，振荡频率，和射流出口角被选择的参数进行研究。选择这些参数是因为它们在流量控制和混合应用中的重要性。结果将提供第一个实验评估的三维，时间分辨的空间振荡射流和横流之间的相互作用，因此作为优化的应用程序，验证数值计算的基础，和未来的研究检查的影响，额外的参数。

Jet in crossflow is a fundamental flow scenario which may be found in several applications such as fuel mixing in combustors, film cooling of turbine blades, or active flow control on wings. The long history of research on this topic provides a comprehensive insight into the fundamental flow field of a steady jet injected into a crossflow. Recently, several studies have been examining spatially oscillating jets emitted by fluidic oscillators in a crossflow. The jets oscillation does not require any moving parts and is solely based on the internal fluid dynamics, which presents one of the main advantages of these devices. In recent years, the effective and efficient application of spatially oscillating jets in crossflow has been impressively demonstrated for mixing enhancement and active flow control. However, despite some suggestions made from rudimentary flow visualizations, the driving mechanisms for the superior performance of spatially oscillating jets are still unknown. However, this information is crucial for a fundamental understanding and a proper optimization process for applications. The three-dimensionality and unsteadiness of this flow field in conjunction with high oscillation frequencies and velocities make experimental and numerical studies challenging. In the proposed work, an experimental study on the fundamental, incompressible flow field of a spatially oscillating jet in interaction with a crossflow is pursued. The jet is emitted by a fluidic oscillator mounted inside a wind tunnel. Flow visualization is used for providing an initial qualitative insight into the flow field. A traversable stereoscopic particle image velocimetry system in combination with established phase-averaging techniques yields the three-dimensional, time-resolved flow field. The quantitative data (e.g., trajectory, vorticity, and flow features) is compared to that of steady jets in crossflow available from the literature. This comparison is expected to reveal commonalities and differences between the flow fields clarifying the driving mechanism for the superior performance and possibly finding new applications. The complexity of this topic requires narrowing down the investigated parameters. In the proposed work, velocity ratio, oscillation frequency, and jet exit angles are selected parameters to be studied. These parameters are chosen due to their importance in flow control and mixing applications. The results will provide the first experimental evaluation of the three-dimensional, time-resolved interaction between a spatially oscillating jet and a crossflow, hence serving as a basis for optimizations in applications, validation of numerical calculations, and future studies inspecting the influence of additional parameters.